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SR770 Manual - Stanford Research Systems

1. 100 Example program using Microsoft GW BASIC and the National 110 Instruments GPIB card Program is equivalent to the C 120 Example program See the comments in the C program 130 140 Use the file DECL BAS provided by National Instruments 150 160 CLEAR 60000 IBINIT1 60000 IBINIT2 IBINIT1 3 BLOAD bib m IBINIT1 170 CALL IBINIT1 IBFIND IBTRG IBCLR IBPCT IBSIC IBLOC IBPPC IBBNA IBONL IBRSC IBSRE IBRSV IBPAD IBSAD IBIST IB DMA IBEOS IBTMO IBEOT IBRDF IBWRTF IBTRAP IBDEV IBLN 180 CALL IBINIT2 IBGTS IBCAC IBWAIT IBPOKE IBWRT IBWRTA IBCMD IBCMDA IBRD IBRDA IBSTOP IBRPP IBRSP IBDIAG IBXTRC IBRDI IBWRTI IBRDIA IBWRTIA IBSTA IBERR IBCNT 185 190 Done with DECL BAS this is our program 200 210 BDNAME FFT770 220 CALL IBFIND BDNAME SR770 find the sr770 230 IF SR770 lt 0 GOTO 770 240 250 WRT rst reset the fft analyzer 260 GOSUB 780 this subroutine sends a command 270 WRT STOP 5 34 ee REMOTE PROGRAMMING 280 GOSUB 780 stop data acquisition in the sr770 290 WRT navg1000 avgo1 turn on 1000 averages 300 GOSUB 780 310 WRT strt and start the average 320 GOSUB 780 330 340 CALL IBRSP SR770 SP poll until no data acquisition in progress average done 350 IF SP MOD 2 0 GOTO 340 360 PRINT Finished Acquiring Spectrum 370 380 DIM BINARY 400 dimension a 400 element integer array 800 bytes 390 V amp HA V 10H linef
2. Se 13 3 DA 1023 cx 2 9 gt gt gt gt gt lt gt lt gt gt qoqa gog e E E ni Gk C0 C0 03 2 ta SR770 FFT SPECTRUM ANALYZER description Set Query the Input to A 0 or A B 1 Set Query the Input Grounding to Float 0 or Ground 1 Set Query the Input Coupling to AC 0 or DC 1 Set Query the Input Range to i dBV full scale 60 lt lt 34 and i is even Set Query the Auto Range mode to Manual 0 or Auto 1 Perform Auto Offset calibration Set Query the Auto Offset Mode to Off 0 or On 1 Set Query the Trigger Mode to Cont 0 Int 1 Ext 2 Ext TTL 3 or source 4 Set Query the Trigger Level to x percent 100 0 lt x lt 99 22 Set Query the Trigger Delay to i samples 13300s i lt 65000 Set Query the Arming Mode to Auto 0 or Manual 1 Manually arm the trigger description Set Query the real time Analysis to None 0 Harmonic 1 Sideband 2 or Band 3 Query result i 0 or 1 of the latest real time analysis Set Query the Harmonic Fundamental to frequency f Hz Set Query the Number of Harmonics to 0 lt i lt 400 Move the Marker or Center Frequency to the next harmonic to the left Move the Marker or Center Frequency to the next harmonic to the right Set Query the Sideband Carrier to f
3. CENTER key Turns Marker Offset on and sets the offset equal to the marker position Set Query the Marker Offset to Off 0 or On 1 Set Query the Marker Offset X value to x Set Query the Marker Offset Y value to x Move the marker to the next peak to the left Move the marker to the next peak to the right Display message s on the screen and sound an alarm description Set Query the Top Reference to x Set Query the Bottom Reference to x Set Query the Vertical Scale Y Div to x AutoScale graph g Similar to the AUTO SCALE key Set Query the Horizontal Expand to no expand 5 128 64 30 15 or 8 bins 4 0 Set Query the Left Bin when expanded to bin i Set Query the X Axis scaling to Linear 0 or Log 1 viii INPUT ISRC 2 i IGND 2 i ICPL i IRNG i ARNG i AOFF AOFM i TMOD 2 i TRLV TDLY i ARMM i ARMS ANALYSIS ANAM g 00 CALC gii FUND 9 9 00 NHRM 2 g 1 NHLT NHRT TSTS i PASF LTBL g 11 12 1 2 LINX 2 i LINS LIDT LLTB LARM 2 i AVERAGING AVGO i NAVG i AVGT i AVGM 2 i OVLP x SOURCE STYP i SLVL i x SFRQ i NTYP i SCAL i APHS PLOT AND PRINT PLOT PTRC AaAanana a annn 2 rls r er dese de CR ER CX
4. This key links the markers on the two traces When the dual trace display format is used linked markers means that the two markers are always at the same location on the graph This is true even if one of the traces is showing the time record This is strictly a graphical function To move the markers activate either trace and use the MARKER key to move the markers with the knob This function turns on the marker offset When marker offset is on a small delta 0 is displayed at the beginning of the marker readout above the graph The marker readout is now relative to the marker offset The marker offset location on the graph is marked with a small star shaped symbol The MARKER REF key toggles the marker offset on and off as well When the MARKER REF key turns on the offset the X and Yoffsets are set to the current marker position Pressing the MARKER REF key again turns the marker offset off This key activates the marker X Offset entry field This is the offset of the marker along the X axis Only numeric entry is permitted The X offset is stored as unitless number When displaying spectra the offset is interpreted as a frequency The X offset does not have to be a frequency which is within the current span 4 18 en MARKER MODE MENU BN Y Offset Next Peak Left Next Peak Right This key activates the marker Y Offset entry field This is the offset of the marker along the Y axis Only numeric entry is permitted
5. AUTO SCALE MARKER MAX MIN d Record the marker Y reading for each range Frequency response is checked at frequencies above 1 kHz The test frequencies are listed below The measurements are performed for two different input ranges Test Frequencies 24 kHz 48 kHz 76 kHz 99 kHz a Set the AC calibrator to 1 kHz and an amplitude of 99 881 mVrms b Set the frequency synthesizer to 1 kHz c Press FREQ lt Center Freq gt 1 lt kHz gt INPUT lt Input Range gt 1 4 lt dBv gt START AUTO SCALE MARKER MAX MIN The Y value of the marker should now read 17 0 dB 0 30 dB d Set the AC calibrator and frequency synthesizer to the frequency in the table Press FREQ Center Freq gt Enter the signal frequency START MARKER MAX MIN f Record the marker Y reading Repeat steps 4d and 4e for all of the frequencies listed 6 9 PERFORMANCE TESTS 4 Now repeat the frequency response measurements at a different input range a Set the AC calibrator to 1 kHz and an amplitude of 6 3021 Vrms b Set the frequency synthesizer to 1 kHz c Press FREQ lt Center Freq gt 1 kHz INPUT lt Input Range gt 2 2 lt dBV gt START AUTO SCALE MARKER MAX MIN MARKER REF The Y value of the marker should now read 19 0 dB 0 30 dB d Repeat steps 4d through 4f above 5 This completes the amplitude accuracy and frequency response test Enter the results of
6. Marker Width Norm Wide Spot Marker Seeks Max Min Mean Grid Div Scm Off 10 Graph Style ure Fil Format Marker On Off Trk Marker Width The Display menu is used to change the graph parameters and marker type The settings for the active trace are displayed in this menu Note that marker movement is activated by the MARKER key and not by this menu DISPLAY The Format key toggles between single and dual trace screen formats The ACTIVE TRACE key toggles the active trace If a single graph is displayed the ACTIVE TRACE switches the graph between 0 and 7 1 If two graphs are displayed ACTIVE TRACE selects either the upper or lower trace as active When the format is switched back to Single the active trace becomes the single displayed trace This function turns the marker on and off or selects tracking mode This function only affects the active trace Each trace has its own marker It is sometimes desirable to turn off the marker before printing the screen When the marker is set to Track the marker automatically seeks the maximum or minimum point of the trace according to the Marker Seeks selection This function selects the width of the marker region defined by the vertical dashed lines on the graph Only the marker for the active trace is affected Normal width is 1 2 of a division Wide is 1 division and Spot is a single X position on the screen the marker
7. Press 2 kHz 10 Press Table Index Press 2 Enter 11 Press X Value Press 2 5 4 kHz 12 Press Insert Item Press Delete Item 13 Press SYSTEM Press Print 14 Press DISPLAY Press Format Highlight the X Value menu box Enter the frequency of the 2nd harmonic into the data table Line 1 now has the frequency of the 2nd harmonic Note how the Y values update with the graph In the Analysis menu many of the frequencies or X values may be entered by copying the X location of the marker using MARKER ENTRY or by entering the numerical value with the keypad Let s add another line to the table Highlight the X Value menu box Enter some frequency which is representative of the noise floor of the signal We decided that we wanted another harmonic in the table This key inserts a new line before the highlighted line We could enter an X value for this new line now But we changed our mind Let s delete this line Display the System menu Display the Printing submenu If we have a printer attached then the Print Data function will print the data table with updated Y values Show the Display menu Choose the Single trace display format This removes the data table display and restores the Screen to a single trace display 1 22 eee GETTING STARTED EN USING LIMIT TABLES A limit table lists the XY coordinates of the line segments
8. ALT RUN STOP STOP Invid The RUN indicator is on whenever data is being taken and spectra are being calculated STOP indicates that data is not being acquired and the data display is not being updated STOP Invid means that the data on the display may not match the graph parameters or the analyzer settings For example if the display is paused using the PAUSE CONT key or some other means and the span is changed clearly the displayed data does not reflect the new span In this case the STOP Invid indicator will turn on SETTLING When changing between narrow frequency spans with long acquisition times the digital filter requires some settling time before all of the data is replaced with new data This time is longer than the record time While this indicator is on the filter is still settling and the displayed spectrum may not be accurate Input Range The input range is always displayed If the range is set manually the display is in normal characters If Auto Range is on then inverse characters are used OvrLoad This indicator turns on if the input signal overloads the analog amplifier or A D converter No Avg Avrging This indicates whether averaging is in effect Averaging affects both traces if they are live If linear averaging is on then the number below the Avrging indicator is the number of averages accumulated so far If averaging is off or exponential then no number is displayed Trigger Trg Wait If t
9. C 1009 5 00225 548 1U AXIAL Capacitor Ceramic 50V 80 20 Z5U AX C 1010 5 00225 548 1U AXIAL Capacitor Ceramic 50V 80 20 Z5U AX C 1011 5 00225 548 1U AXIAL Capacitor Ceramic 50 80 20 Z5U C 1012 5 00225 548 1U AXIAL Capacitor Ceramic 50V 80 20 Z5U AX C 1013 5 00225 548 10 AXIAL Capacitor Ceramic 50V 80 20 Z5U AX 1014 5 00100 517 2 20 Capacitor Tantalum 35V 20 Rad C 1015 5 00225 548 AXIAL Capacitor Ceramic 50V 80 20 Z5U AX C 1016 5 00225 548 10 AXIAL Capacitor Ceramic 50 80 20 Z5U C 1017 5 00225 548 1U AXIAL Capacitor Ceramic 50V 80 20 Z5U AX 7 9 REF 1018 1019 C 1020 1021 1022 1023 1024 1025 1026 1027 1028 C 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 C 1039 1040 1041 1042 1043 1044 CU901 D 100 D 401 D 601 D 602 D 603 D 604 D 605 D 606 D 607 D 608 D 701 D 702 D 703 D 704 D 705 D 810 JP201 JP301 JP302 JP303 JP601 JP603 JP702 SRS PART 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00100 517 5 00225 548 5 00225 548 5 00100 517 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00100 517 5 00225 548 5 00225 548 5 00225 548 5 00100 517 5 00225 548 5 00225 548 5 00114 501 3 00391 301 3 00004 301 3 00004 301 3 00004 301 3 00004 301
10. Only segments or the portions of segments within the frequency span are tested Limits outside the span are ignored This key activates the Table Index entry field Knob adjustment and numeric entry are both permitted When using the knob scrolling past the last index will add a new line If an index greater than the last index is entered then a new line is added after the end of the table New segments are generated with Xbegin equal to Xend of the previous segment and the same X span The Y values are set to the value of Y2 for the previous segment This simplifies the building of a continuous limit table 4 42 en ANALYZE MENU X Values Y Values Limit Type More Return If the table is longer than what can be displayed in the window then the table index can be used to scroll the window Entering an index will always display that line in the window for viewing or editing This key activates the selected X Value entry field Pressing the key again toggles to the other X value The upper value is Xbegin and the lower value is Xend The X values of the highlighted line may be entered using the numeric keypad No knob adjustment is allowed When this field is active the MARKER ENTRY key will copy the marker X position into this field This key activates the selected Y Value entry field Pressing the key again toggles to the other Y value The upper value is Y1 and the lower value is Y2 The Y values of the highlight
11. Press lt Coupling gt to choose DC Press lt Input Range gt Press 4 lt dBV gt 4 Press DISPLAY Press lt Format gt to choose Up Dn 5 Press MEAS Press lt Measure Menu gt Press lt Time Record gt Press lt Return gt Press lt Display Menu gt Press lt Linear Mag gt 6 Press INPUT Press lt Trigger Menu gt Press lt Trigger gt to select Internal Press lt Trigger Level gt When the power is turned on with the backspace key depressed the analyzer returns to its default settings See the Default Settings list in the Menu section of this manual for a complete listing of the settings The input impedance of the analyzer is 1 The generator may require a terminator Many generators have either a 50 1 or 600 O output impedance Use the appropriate feedthrough termination if necessary In general not using a terminator only means that the output amplitude will not agree with the generator setting and the distortion may be greater than normal Let s choose DC coupling and an input range that doesn t overload Set the input range to 4 dBV Adjust the pulse amplitude so that no overloads occur Show two traces We will show the time record on the upper trace Go to the Measure menu to choose Time Record Let s show the time record on a linear scale Now set up the trigger Trigger on the signal itself The input is a 1 V pulse so set the trigger level to 1 11 GETTIN
12. backspace key Wait until the power on When the power is turned on with the backspace key depressed the analyzer returns to its default tests are completed Connect the SR770 Source output to the A input Press SOURCE Press lt Sine gt Press lt Configure Source gt Press lt Level gt Press 3 lt dBV gt Press AUTO RANGE Press SPAN DOWN until the span is 6 25 kHz Press AUTO SCALE Press MEAS Press lt Calculator Menu gt Press lt Do Calc gt 8 Press DISPLAY settings See the Default Settings list in the Menu section for a complete listing of the settings Display the Source menu Turn on the Sine output Display the Sine frequency and level Select the Sine output level Enter 3 dBV for the Sine output level Note that the Sine level can be entered in either mV pk or dBV pk Let the analyzer automatically set its input range Set the span to display the 1 kHz signal and its first few harmonics Set the graph scaling to display the entire range of the data Display the Measure menu Select the Calculator menu This operation defaults to adding zero to the trace data The default operation is the default argument is the constant zero We re doing this so that the trace does not update This is now the graph we will use as the reference data Reference data normally comes from a disk file Recalling a stored file brings the data back to the active graph b
13. progress When the command execution terminates the Interface Ready bit is set again and new commands will be processed Since most commands execute very quickly the host computer does not need to continually check the Interface Ready bit Commands may be sent one after another and they will be processed immediately However some commands such as file commands and math operations may require a long time to execute In addition the host program may need to check that these operations executed without error In these cases after the command is sent the Status Bytes should be queried 5 2 When using the GPIB interface serial polling may be used to check the Interface Ready bit in the Serial Poll Byte while an operation is in progress After the Interface Ready bit becomes set signalling the completion of the command then the ERR bit may be checked to verify successful completion of the command If the RS232 interface is used or serial polling is not available then the STB ESR ERRS and FFTE status query commands may be used to query the Status Bytes Since the 5 770 processes one command at a time the status query will not be processed until the previous operation is finished Thus a response to the status query in itself signals that the previous command is finished The query response may then be checked for various errors For example the command line SVTR ERRS lt will save the data to disk and return th
14. 3 0103 double rxBufffi 512 0 5 32 ee REMOTE PROGRAMMING To calculate absolute dBV from dB relative to full scale we need to query the full scale input range txsr770 IRNG ibrd sr770 tstr 30 sscanf tstr ld amp full_ scale full_scale input range in dBV for i 0 i lt 400 i dbs i full scale printf 6d 01 4 0050 getch f wait for keypress alternatively we can read the spectrum point by point using the ASCII SPEC g i command for i 0 i lt 400 i sprintf tstr SPEC 0 d i construct each query string txsr770 tstr ibrd sr770 tstr 30 read each point back in ASCII sscanf tstr lf amp dbs i convert ASCII string to a value printf 6d 96fin i dbs i end of main program void txsr770 char str function to send a command to the sr770 char serPol ibwrt sr770 str strlen str do ibrsp sr770 amp serPol now poll for IFC RDY to ensure completion of the command while serPol amp 2 0 f before returning 5 33 REMOTE PROGRAMMING EXAMPLE PROGRAM 2 Using BASIC with the National Instruments GPIB card on the IBM PC To successfully interface the SR770 to a PC via the GPIB interface the instrument interface card and interface drivers must all be configured properly To configure the SR770 the GPIB address must be set in the SETUP menu The default GPIB address is 1
15. DATA TABLE COMMANDS The Data Table commands listed below require that the data table display be active The commands affect the displayed table and thus the active trace only TABL DTBL i 6f DINX 2 i DINS DIDT DLTB The TABL command activates the data table for the active trace The screen display changes to the data table display To turn off the data table set the display back to single trace mode The DTBL command sets or queries the data table The DTBL command queries the entire table The data is returned in the form X1 Y1 X2 Y2 X3 Y3 If where Xn Yn are the table X and Y entries for line n The Y values are taken from the latest trace Any Y value which corresponds to and X value not within the span returns the value 1 23E 034 The DTBL i command queries the X and Y values for line i only The data is returned in the from XY If The DTBL i f command sets the X value of line i to f Remember that the X values have no units However they are usually frequencies and as such the parameter f is a real number of Hz If i is greater than the last line number in the table the new line is added to the end of the table The DINX command sets or queries the table index The parameter i ranges from 0 to 199 If i is greater than the last index in the table then a new line is added to the end of the table The DINS command inserts a new line before the table index the highlighted line The new line beco
16. Now we have 2 traces which differ in amplitude Let s take the ratio Go back to the Calculator menu We will divide the active graph Trace1 Live by the inactive graph TraceO reference Select the divide operation Do the calculation Since the graphs are displayed in dBV the ratio of the peaks should simply be the difference in their amplitudes expressed in dBV Remember the calculations work on the underlying 1 29 ENN GETTING STARTED M data points in Volts The active graph now displays the ratio of the two traces in dB Press AUTO SCALE The marker on the lower graph should read the difference between the two peak amplitudes 17 0 dB Clearly only the frequencies which correspond to the signal and its harmonics have much meaning in this ratio One noise floor divided by another noise floor is going to be pretty noisy A better way to read these harmonic ratios is using the data table A data table can display the values of selected frequencies in easy to read form See Using Data Table earlier in this section The data table would be defined for Trace1 Other operations which may be performed are x square root log phase unwrap and d dx The second argument may be a constant for scaling or offset 201 0 differentiate or integrate the spectrum or the other graph reference trace from disk 1 30 een GETTING STARTED EN USING THE SOURCE The SR770 has a built in signal sour
17. Procedure 1 PRESET Turn the analyzer off wait a few seconds then back on with the key pressed 2 Setthe frequency synthesizer to a frequency of 10 kHz and an amplitude of 400 mVrms 3 Press the keys in the following sequence INPUT Input Range 2 lt Trigger Menu gt lt Trigger gt Select Internal Trigger AUTO SCALE DISPLAY lt Format gt Select Up Dn lt Marker Width gt Select Spot MARKER MAX MIN ACTIVE TRACE DISPLAY lt Marker Width gt Select Spot MEAS lt Display Menu gt lt Phase gt ACTIVE TRACE MARKER MODE lt Linked Markers gt Select On AVERAGE lt Number of Averages gt 2 0 lt Enter gt 6 15 PERFORMANCE TESTS lt Average Type gt Select Vector lt Averaging gt Select On 4 Record the marker Y reading for Trace1 lower trace Y reading in degrees 5 Press INPUT lt Trigger Menu gt lt Trigger Slope gt Select Falling Edge START 6 Record the marker Y reading for Trace1 in degrees 7 This completes the phase accuracy test Enter the results of this test in the test record at the end of this section 6 16 eee PERFORMANCE TESTS 9 Harmonic Distortion This test measures the harmonic distortion of the analyzer Setup We will use the low distortion oscillator to provide the signal Connect the output of the low distortion oscillator to the A input of the analyzer Be sure to use the appropri
18. Turn the knob to change the vertical scale to 0 5 dB div mode The spectra are taken with no overlap at all spans but without using the trigger circuits When each time record finishes the next one begins without delay Any signal which is EXACTLY periodic over a time record will be the same in EVERY time record For this type of signal this has the same effect as triggering We need to use source triggering in order to get phase information from this spectrum Go back to the main Input menu Turn off Auto Offset In order to preserve the phase information from source triggering we need to turn off Auto Offset calibration The SR770 does not synchronize phase when turning the source on and off Hence the phase of the chirp components will be stable but arbitrary The Auto Offset calibration interrupts the input and restarts data acquisition without synchronization Thus the phases of the components will change whenever Auto Offset calibration occurs disrupting our measurements Show the Scale menu Highlight the Y vertical scale Zoom in so that the ripple in the spectrum is easily visible This spectrum has very little ripple If this source was the input to a device under test the output spectrum would be the amplitude transfer function of the device The chirp source is digitally synthesized and passes through an output reconstruction filter The Source Cal feature adjusts the input calibrations to compensate for
19. 3 00004 301 3 00004 301 3 00004 301 3 00004 301 3 00004 301 3 00203 301 3 00004 301 3 00004 301 3 00004 301 3 00004 301 3 00820 301 0 00772 000 0 00772 000 0 00772 000 0 00772 000 1 00113 100 0 00772 000 1 00083 130 VALUE AXIAL AXIAL AXIAL AXIAL AXIAL 2 2U AXIAL AXIAL 2 2U AXIAL AXIAL AXIAL AXIAL AXIAL AXIAL AXIAL AXIAL AXIAL AXIAL AXIAL 2 2U AXIAL AXIAL AXIAL 2 2U AXIAL AXIAL 200P MBR360 1N4148 1N4148 1N4148 1N4148 1N4148 1N4148 1N4148 1N4148 1N4148 1N5711 1N4148 1N4148 1N4148 1N4148 1N5228B 1 5 WIRE 1 5 WIRE 1 5 WIRE 1 5 WIRE DIN 5 1 5 WIRE 26 PIN DIL PARTS LIST DESCRIPTION Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Tantalum 35V 20 Rad Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Tantalum 35V 20 Rad Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic
20. 4 00034 401 4 00034 401 4 00034 401 4 00034 401 4 00063 401 4 00080 401 4 00080 401 4 00021 401 4 00056 401 4 00079 401 4 00022 401 4 00062 401 4 00060 401 4 00081 401 4 00031 401 4 00021 401 4 00021 401 4 00053 401 4 00038 401 VALUE 20 PIN DIL 1 5 WIRE 3 PIN SI 30 PIN DRA 34 PIN DRA GPIB SHIELDED RS232 25 PIN D 26 PIN ELH 5 PIN WHITE 10KX7 10KX5 10KX5 22KX9 1 0KX5 10KX5 150X5 10KX4 003 015 CONTRLR 2N5210 2N3906 2N3904 2N3904 2N3906 2N3906 2N3904 10K 4 7K 10K 10K 10K 51K 1 0K 10K 10K 10K 10K 3 0K 47 47 1 0K 22 4 7K 1 0M 270 240 470 100 1 0K 1 0K 200 120 DESCRIPTION Connector Male Hardware Misc Connector Male Connector Male Right Angle Connector Male Right Angle Connector IEEEA88 Reverse R A Female Connector D Sub Right Angle PC Female Connector Male Header Amp MTA 156 Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Res Network SIP 1 4W 2 Isolated Printed Circuit Board Transistor TO 92 Package Transistor TO 92 Package Transistor TO 92 Package Transistor TO 92 Package Transistor TO 92 Package Transistor TO 92 Package Transistor TO 92 Package Resistor Carbon Film 1 AW 5 Resistor
21. 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Tantalum 35V 20 Rad Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Tantalum 35V 20 Rad Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic Disc 50V 10 SL Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Hardware Misc Hardware Misc Hardware Misc Hardware Misc Connector Misc Hardware Misc Connector Male 7 10 eee PARTS LIST REF JP801 JP802 JP803 JP901A JP901B JP902 JP903 JP1000 JP1002 N 101 N 102 N 501 N 601 N 701 N 801 N 901 N 902 PC1 Q 401 Q 701 Q 702 Q 703 Q 705 Q 810 Q 811 R 401 R 402 R 502 R 601 R 602 R 701 R 702 R 703 R 704 R 705 R 706 R 707 R710 R711 R712 R713 R714 R 801 R 802 R 808 R 809 R 810 R 811 R 812 R 813 R 814 SRS PART 1 00035 130 0 00772 000 1 00086 130 1 00207 133 1 00209 133 1 00238 161 1 00016 160 1 00170 130 1 00039 116 4 00587 425 4 00334 425 4 00334 425 4 00227 425 4 00270 425 4 00334 425 4 00221 425 4 00244 421 7 00809 701 3 00026 325 3 00022 325 3 00021 325 3 00021 325 3 00022 325 3 00022 325 3 00021 325 4 00034 401 4 00079 401 4 00034 401 4 00034 401 4 00034 401 4 00088 401 4 00021 401
22. C 524 C 525 C 526 C 527 C 528 C 529 C 530 C 531 C 533 C 534 C 535 C 536 C 537 C 538 C 539 D 101 D 102 D 103 D 104 D 105 D 106 D 107 D 108 D 109 D 110 D 111 D 112 D 301 D 302 D 303 D 304 J 101 J 102 JP401 JP402 JP503 K 101 K 102 K 103 K 104 K 105 SRS PART VALUE 5 00100 517 2 20 5 00260 544 4700 5 00023 529 1U 5 00260 544 4700 5 00023 529 1U 5 00100 517 2 20 5 00100 517 2 20 5 00260 544 4700 5 00023 529 1U 5 00260 544 4700 5 00023 529 1U 5 00023 529 1U 5 00023 529 1U 5 00100 517 2 20 5 00100 517 2 20 5 00100 517 2 20 5 00023 529 1U 5 00100 517 2 20 5 00023 529 1U 5 00225 548 10 AXIAL 5 00225 548 10 AXIAL 5 00225 548 1U AXIAL 5 00225 548 1U AXIAL 5 00100 517 2 20 5 00100 517 2 20 3 00457 301 1N5241B 3 00004 301 1N4148 3 00004 301 14148 3 00004 301 1N4148 3 00004 301 14148 3 00004 301 14148 3 00004 301 14148 3 00004 301 1N4148 3 00004 301 1N4148 3 00004 301 1N4148 3 00004 301 1N4148 3 00004 301 1N4148 3 00004 301 1N4148 3 00004 301 1N4148 3 00293 301 1N5226B 3 00293 301 1N5226B 0 00388 000 PHONO 0 00388 000 PHONO 0 00772 000 1 5 WIRE 0 00772 000 1 5 WIRE 0 00772 000 1 5 WIRE 3 00239 335 5 212 12 3 00239 335 5 212 12 3 00239 335 5 212 12 3 00239 335 5 212 12 3 00239 335 5 212 12 DESCRIPTION Capacitor Tantalum 35V 20 Rad Cap Mini Electrolytic 25V 20 Radial Cap Monolythic Ceramic 50V 20 Z5U Cap Mini Electrolytic 25V 2
23. Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Electrolytic 35V 20 Rad Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Diode Diode Hardware Misc Hardware Misc Relay 7 17 EN PARTS LST REF K 302 N 301 N 501 N 502 N 601 N 602 N 603 PC1 Q 301 Q 302 R 101 R 201 R 301 R 302 R 303 R 304 R 305 R 306 R 307 R 501 R 502 R 503 R 504 R 505 R 506 R 507 R 508 R 509 R 510 R 511 R 512 R 513 R 514 R 515 R 516 R 517 R 518 R 519 R 524 R 525 R 526 R 527 R 528 R 530 R 531 R532 R 542 R 543 R 602 R 603 R 610 SRS PART 3 00196 335 4 00284 421 4 00262 425 4 00262 425 4 00468 420 4 00255 421 4 00255 421 7 00351 701 3 00022 325 3 00022 325 4 00079 401 4 00079 401 4 00034 401 4 00034 401 4 00034 401 4 00142 407 4 00034 401 4 00030 401 4 00030 401 4 00772 402 4 00772 402 4 00177 407 4 00771 407 4 00163 407 4 00409 408 4 00409 408 4 00467 407
24. Knob Main Memory Video Memory DSP Test 2 DC Offset Input Range 30 dBV 60 dBV Reading 3 Common Mode Rejection Input Range 2 dBV Frequency 1 0 kHz Reading Date Upper Limit lt 85 dBV lt 85 dBV 4 Amplitude Accuracy and Flatness Input Range 46 dBV 38 dBV 30 dBV 14 dBV 4 dBV 10 dBV Calibrator Ampl 2 509 mVrms 6 302 mVrms 15 830 mVrms 99 881 mVrms 0 7934 Vrms 1 5830 Vrms Flatness relative to 1 kHz Input Range 14 dBV 14 dBV 14 dBV 14 dBV Frequency 24 kHz 48 kHz 76 kHz 99 kHz Lower Limit 49 20 dBV 41 20 dBV 33 20 dBV 17 20 dBV 0 80 dBV 6 80 dBV Lower Limit 17 30 dBV 17 30 dBV 17 30 dBV 17 30 dBV Tested By Upper Limit 80 dB Reading Reading Upper Limit 48 80 dBV 40 80 dBV 32 80 dBV 16 80 dBV 1 20 dBV 7 20 dBV Upper Limit 16 70 dBV 16 70 dBV 16 70 dBV 16 70 dBV 6 23 PERFORMANCE TESTS M SR770 Performance Test Record 4 Amplitude Accuracy and Flatness Continued Flatness relative to 1 kHz Input Range Frequency Lower Limit Reading Upper Limit 22 dBV 24 kHz 0 3 dBV 0 3 dBV 22 dBV 48 kHz 0 3 dBV 0 3 dBV 22 dBV 76 kHz 0 3 dBV 0 3 dBV 22 dBV 99 kHz 0 3 dBV 0 3 dBV 5 Amplitude Linearity Input Range Calibrator Ampl Lower Limit Reading Upper Limit 22 dBV 6 3021 Vrms 18 80 dBV 19 20 dBV 1 1207 Vrms 3 80 dBV 4 20 dBV 141 09 mVrms 14 21 dBV 13 80 dBV 22 361 mVrms 30 82 dB
25. On Number Averages Average Type Vector Peak Hold Average Mode Linear Exponential Overlap 10 0 Averaging On Off Number of Averages The Average menu selects trace averaging number of averages type of averaging and amount of overlap The averaging parameters apply to both traces AVERAGE Note The START key starts an average The PAUSE CONT key will pause an average in progress Pressing PAUSE CONT again will resume the average where it was paused Pressing the START key always resets the average before restarting With wide frequency spans the high real time bandwidth of the SR770 allows many averages to be completed between each screen update For small numbers of averages averaging is almost instantaneous This key turns Averaging on and off The Avrging No Avg indicator at the bottom of the screen shows the state of this function This key activates the Number of Averages entry field for both numeric entry and knob adjustment This is the number of spectra which are averaged together in linear averaging and the weighting factor for exponential averaging The number of averages allowed ranges from 2 to 32 767 Changing the number of averages while in the RUN mode resets the averages and starts over If the analyzer is stopped then the average is not reset nor restarted 4 45 AVERAGE MENU Average Type Average Mode This function selects the Aver
26. Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Wire Wound Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Wire Wound Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Header Amp MTA 156 Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Voltage Reg TO 220 TAB Package Voltage Reg TO 220 TAB Package Voltage Reg TO 220 TAB Package Voltage Reg TO 220 TAB Package Voltage Reg TO 220 TAB Package Voltage Reg TO 220 TAB Package Voltage Reg TO 220 TAB Package Voltage Reg TO 220 TAB Package Tie Screw Panhead Phillips Screw Panhead Phillips Washer nylon Washer nylon Screw Panhead Phillips Insulato
27. TAB Package Q7 3 00378 329 102 Voltage Reg TO 220 TAB Package Q8 3 00257 329 41 Voltage Reg TO 220 TAB Package R3 4 00034 401 10K Resistor Carbon Film 1 4W 5 R4 4 00032 401 100K Resistor Carbon Film 1 4W 5 R5 4 00034 401 10K Resistor Carbon Film 1 4W 5 7 14 eee PARTS LIST EMEN REF R6 R7 R8 R9 R 10 R 11 R 12 R 13 R 14 R15 R 16 R17 R 18 R 19 SRS PART 4 00046 401 4 00065 401 4 00021 401 4 00021 401 4 00436 409 4 00446 407 4 00054 401 4 00034 401 4 00034 401 4 00021 401 4 00021 401 4 00436 409 4 00770 407 4 00054 401 4 00034 401 4 00034 401 4 00360 401 4 00048 401 4 00360 401 4 00027 401 4 00027 401 4 00185 407 4 00185 407 4 00522 407 4 00517 407 4 00522 407 4 00517 407 1 00152 116 3 00039 340 3 00319 340 3 00088 340 3 00088 340 3 00119 329 3 00346 329 3 00346 329 3 00330 329 3 00149 329 3 00141 329 3 001 14 329 3 00120 329 0 00089 033 0 00186 021 0 00187 021 0 00231 043 0 00246 043 0 00309 021 0 00316 003 1 00087 131 7 00285 721 0 00158 070 VALUE 2 0M 3 3K 1 0K 1 0K 0 1 47 5K 200K 10K 10K 1 0K 1 0K 0 1 38 3K 200K 10K 10K 430 2 2K 430 1 5K 1 5K 4 02K 4 02K 243 3 57K 243 3 57K 11 PIN WHITE 74HC14 AD586JN LF353 LF353 7905 7812 7812 7912 LM317T LM337T 7815 7915 4 6 32X1 3 8PP 4 40X1 4PP 1 32 4 SHOULD 8 X 1 16 8 32X1 4PP PLTFM 28 2 PIN JUMPER PLTFM 21 60MM 24V DESCRIPTION
28. The offset is stored as a unitless number If the display units are changed then the Y offset needs to be changed The Y offset does not have to be a value which is currently within the vertical span of the graph This function moves the marker to the next peak to the left of the current marker position This function moves the marker to the next peak to the right of the current marker position 4 19 Inout Source Grounding Float Ground Coupling AC Input Range 2 dBV Trigger Menu Auto Offset Input Source Grounding Coupling The Input menu is used to change the input configuration and input range In addition the Trigger and Arming submenus set the triggering mode level and delay INPUT Input Source Trigger Source Arming Mode Trigger Level Trigger Slope Grounding Coupling Input Range Trigger Delay Trigger Menu Arming Menu Auto Offset The Input Source key selects the front end signal input configuration The input amplifier can be single ended A or differential A B In general when looking at very small signals connect A to the signal source and B to the signal source ground and use A B In this case make sure that the two input cables do not encompass any loop area twist them together or run them side by side This key chooses the shield grounding configuration The shields of the input connectors A and B are
29. The other trace must be measuring spectrum PSD or time record 4 5 MEASURE MENU Se To choose the number of bands displayed the starting band and the weighting Bands function use the FREQ menu The FREQ menu will display the band selection 30 menu shown the right whenever octave analysis is on Starting Band ex Weighting The Bands key toggles the octave analysis range between 15 30 bands The bands are always 1 3 octave Starting Band Pressing this key activates the Starting Band number entry field The SR770 can display bands 2 through 49 The starting band can range from 2 to 49 minus the number of bands 15 or 30 Weighting The Weighting key toggles between no weighting and A weighting A weighting compensates for auditory sensitivity and can provide data comparable to that derived from analog analysis equipment Return The Return key will return to the main MEAS menu 4 6 en MEASURE MENU EN Display Log Linear Mag e Real Part Imag Part Return Log Mag Linear Mag Real Part Imag Part The Display sub menu allows the user to choose the displayed quantity for the active trace Display This key displays the magnitude of the measurement on a logarithmic scale Only the active trace display is affected Both the Time Record as defined in this analyzer and the corresponding FFT are complex quant
30. Z5U Capacitor Ceramic Disc 50V 10 SL Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Ceramic 50V 80 20 Z5U AX Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad 7 20 eee PARTS LIST EMEN REF 274 C 301 C 302 C 303 C 304 C 305 C 306 C 307 C 308 C 309 C 310 C 311 C 350 C 351 C 352 C 353 C 354 C 355 C 356 C 357 C 358 C 359 C 360 C 361 C 363 C 364 C 365 C 401 C 402 C 403 C 404 C 405 C 406 C 407 C 408 C 409 C 410 C 411 C 412 C 413 C 414 C 415 C 416 C 417 C 418 C 503 C 509 C 510 C 511 C 512
31. display change the Format in the Display menu back to Single 4 30 en ANALYZE MENU Harmonic Fundamental 10 0000 kHz Harmonics Next Harmonic o Return Fundamental Harmonics Next Harmonic Left The Harmonic analysis submenu turns on real time harmonic analysis and sets the fundamental frequency and number of harmonics Functions also automatically move the span center frequency to adjacent harmonics ANALYZE Fundamental Next Harmonic Left Next Harmonic Right Return This key activates the fundamental frequency entry field If no real time analysis was on when the harmonic submenu was entered then this field is automatically filled with the marker frequency The Marker Entry key copies the marker frequency into this field even when it is not activated When this field is activated knob adjustments and numeric entry are permitted Note that marker entries and knob adjustments are done with the resolution of the current frequency span If the actual fundamental is not exactly equal to a frequency bin then higher harmonic frequencies will be more and more inaccurate In this case the frequency should be entered numerically with as much precision as necessary The harmonic frequency bins on the graph are identified by a small triangle marker located at the Y positions of each harmonic bin This is helpful in determining whether the fundamental frequency is accurat
32. harmonic distortion and common mode rejection CMR To provide such performance a FET input differential amplifier with common mode feedback architecture was chosen The input signal is first passed through a series of relays to select input mode input coupling and input attenuation The 30 dB input attenuator formed by resistors R102 R105 serves to attenuate very large signals that enter the instrument but also serves a dual purpose of providing protection to the input FETs in the presence of very high voltages 75Vpk To prevent damage to the input FETs the input voltage is monitored by comparator U105 High voltages cause the input attenuator to be automatically engaged regardless of the user gain setting at the front panel Resistors R107 and R108 provide some input protection to the input FETs with only a slight penalty in input voltage noise The input FETs U100A and U100B are extremely low noise matched FET s with a voltage input noise of approximately 3 5 nv VHz To improve distortion performance the input FETs are cascoded to maintain a constant drain source voltage across each FET This prevents modulation of the drain source voltage by the input voltage U104 senses the source voltage and maintains the same voltage at the drain with some DC offset determined by resistors R113 R116 and R120 R123 U103 provides common mode feedback and maintains a constant drain current in each FET The gain of the front end is either 2 o
33. is exactly equal to one time record So setting the delay to half of a time record will place the pulse at the middle of the record Remember that the time record only displays the first 400 points out of 512 so that the middle of the record is not the middle of the display trace The spectrum should reappear on the lower trace This is because windowing preserves the central part of the time record eee GETTING STARTED EN 10 Press 4 7 5 Samples 11 Press Trigger to select Continuous 12 Press MEAS Press Window Press Uniform Lets delay the signal some more Now we ve delayed the time record by almost a full period The pulse is now near the end of the time record Notice how the spectrum is greatly attenuated This is the effect of the window function attenuating the start of the timer record Now if we go to continuous triggering the time record becomes unstable The spectrum is also unstable because of the windowing Some time records place the pulse at the middle some at the ends If we set the window back to Uniform we find that the spectrum does not vary with the position of the pulse within the time record ENN GETTING STARTED M USING THE DISK DRIVE The disk drive on the SR770 may be used to store 3 types of files 1 Data File This includes the data in the active trace the measurement and display type the units and the graph scaling In addition the associated data and
34. lt Argument gt Press 9 0 0 0 0 lt Enter gt Press lt Do Calc gt Press AUTO SCALE Highlight the argument denominator 360 x 250 Hz 90000 sec 1 Convert the curve to group delay in seconds The graph still reads out in degrees though the actual units are now sec The calculator does math with numbers not units We need to remember the appropriate units to assign to the marker The group delay varies between 1 9 ms to 1 9 ms Using the chirp source the SR770 can measure amplitude and phase transfer curves for a device under test The amplitudes are calibrated using the Source Cal mode The phase spectrum can be calibrated to zero at any time using the Auto Phase function Phases relative to the stored phase curve are displayed live This gives the SR770 the functionality of a network analyzer with only a single input channel 1 46 eee GETTING STARTED EN THINGS TO WATCH OUT FOR If the analyzer is on but doesn t seem to be taking data there are a number of things to check 1 Press the START key to make sure that the indicator at the lower left of the screen displays RUN instead of STOP 2 Check if linear averaging is on When the analyzer finishes a linear average of N spectra the analyzer stops and the data is no longer updated Press START to take another average 3 Make sure the triggering mode is CONTinuous Otherwise the analyzer may be waiting for a trigger as shown by the Trg
35. single frequency or time bin The Marker Position displays the X position frequency or time and the Y data of the marker Pressing the MARKER key will draw a box around the marker information When the marker readout is surrounded by this box the spin knob adjusts the position of the marker region The marker region moves in increments of one frequency or time bin MENU DISPLAY The Soft Key menu boxes define the functions of the 6 soft keys to the right of the screen The menu boxes are grouped into menus Pressing each of the ten Menu keys will display a different menu of boxes Related functions are grouped into a single menu In general pressing a soft key does one of two things One is to toggle between 2 or 3 specific choices An example is the Display Format box illustrated on the previous page Pressing the first Soft key toggles the display between Single and Up Dn The second soft key mode is to highlight an entry field and knob function An example would be the Start Freq Pressing the soft key will highlight the Start Freq value The Start Freq may then be adjusted with the knob or entered as a value using the numeric entry keys Each menu is described at length in a following section STATUS INDICATORS In addition to the data display and menu boxes there are a number of status indicators which are displayed at the bottom of the screen 3 6 RUN AutoRng Avrging Trg Wait Settling OvrLoad BIS
36. the start of data collection by the SR770 so that the resulting transient is captured in one FFT time record The Trigger input can be a TTL level signal or an analog signal T301 provides some common mode rejection for the trigger input Relay K302 selects TTL or Analog Level Trigger Relay K301 allows the trigger signal to come from the output CIRCUIT DESCRIPTION of the analog front end amplifiers or the external TRIGGER front panel BNC Trigger signals pass through the 74F86 XOR gate where it can be inverted if falling edge trigger slope is selected TTL triggers proceed directly to the F86 XOR gate via some input protection Analog level signals are first converted to a TTL signal via high speed comparator U303 and then proceed to the F86 XOR gate At the heart of the trigger input is the analog high speed comparator U303 LT1016 It s input is buffered by U301A and protected by resistor N301A and diodes D301 and D302 C301 provides high frequency hysteresis when the output latch cannot respond fast enough and U301B and U302A provide low frequency hysteresis R304 and N301B determine the level of hysteresis The DC trigger level is set by the 8 bit DAC U513B U515 buffers the DAC output and provides a DC offset to correct the offset from the anti aliasing filter U304 guarantees that triggers occur on the next rising edge of the output from XOR gate U302B Flip Flops U304B and U305A synchronize the trigger sign
37. until the span is 6 25 kHz 5 Press AUTO SCALE 6 Press ANALYZE Press Data Table 7 Press MARKER MAX MIN Press X Value Press MARKER ENTRY 8 Press Table Index Press 1 Enter 1 21 When the power is turned on with the backspace key depressed the analyzer returns to its default settings See the Default Settings list in the Menu section for a complete listing of the settings Display the Source menu Turn on the Sine output Leave the sine frequency and level at the default settings 1 kHz and 1 Vpk Let the analyzer automatically set its input range Set the span to display the 1 kHz signal Set the graph scaling to display the entire range of the data Display the Analysis menu Select Data Table display The display switches to dual trace format with the spectrum on top and the data table listed below This moves the marker to the peak of the spectrum This should center the marker on the 1 kHz fundamental frequency Highlight the X Value menu box This copies the marker X position into the X Value menu box The X value of data table line 0 is now equal to the 1 kHz signal frequency The Y value of line is updated each time the graph is updated This highlights the Table Index menu box Let s add another line to the data table Entering an index or line number beyond the end of the table adds a new line to the end ENN GETTING STARTED ee 9 Press lt X Value gt
38. 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 7 24
39. 2 2 points at 128 kHz or half of the input rate 256 KHz The net result is the digital filter outputs a time record of 1024 points effectively sampled at 128 kHz to make up an 8 ms record The FFT processor operates on a constant number of points and the resulting FFT will yield 400 points from dc to 50 kHz The resolution or linewidth is 125 Hz This process of doubling the time record and halving the span can be repeated by using multiple stages of digital filtering The SR770 can process spectra with a span of only 191 mHz with a time record of 2098 seconds if you have the patience However this filtering process only yields baseband measurements frequency spans which start at dc Starting the span somewhere other than dc Besides being able to choose the span and resolution of the spectrum we would also like the span to be able to start at frequencies other than dc It would be nice to center a narrow span around any frequency below 100 kHz Using digital filtering alone requires that every span start at dc What is needed is heterodyning is the process of multiplying the incoming signal by a sine wave The resulting spectrum is shifted by the frequency of the sine wave If we incorporate heterodyning with our digital filtering we can shift any frequency span so that it starts at dc The resulting FFT yields a spectrum offset by the heterodyne frequency When this spectrum is displayed the frequencies o
40. 208 R 209 R 210 R 211 R 212 R 213 R 214 R 216 R 217 R 218 R 219 R 250 R 251 R252 R 253 R 256 R 259 R 260 R 261 R 262 R 263 R 264 R 265 R 266 R 267 R 268 R 269 SRS PART 4 00034 401 4 00030 401 4 00030 401 4 00030 401 4 00030 401 4 00142 407 4 00619 408 4 00619 408 4 00234 407 4 00138 407 4 00411 407 4 00411 407 4 00138 407 4 00722 401 4 00042 401 4 00141 407 4 00141 407 4 00196 407 4 00185 407 4 00206 407 4 00130 407 4 00130 407 4 00210 407 4 00130 407 4 00653 407 4 00737 407 4 00661 407 4 00665 407 4 00302 407 4 00736 407 4 00169 407 4 00138 407 4 00663 407 4 00663 407 4 00138 407 4 00141 407 4 00141 407 4 00141 407 4 00141 407 4 00141 407 4 00141 407 4 00141 407 4 00141 407 4 00141 407 4 00141 407 4 00141 407 4 00030 401 4 00030 401 4 00030 401 4 00030 401 4 00030 401 VALUE 10K 10 10 10 10 100K 909 909 10 10 0K 1 37K 1 37K 10 0K 43K 15K 100 100 6 04K 4 02K 8 06K 1 00K 1 00K 9 09K 1 00K 205 162 130 102 82 5 64 9 10 0K DESCRIPTION Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W
41. 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 35V 20 Rad Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 35V 20 Rad Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 35V 20 Rad Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 35V 20 Rad Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 35V 20 Rad Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 35V 20 Rad Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 35V 20 Rad Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 35V 20 Rad Cap Mini Electrolytic 25V 20 Radial Cap Mini Electrolytic 25V 20 Radial Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 35V 20 Rad 7 21 EN PARTS LST REF C 514 C 515 C 516 C 517 C 518 C 519 C 520 C 521 522 C 523
42. 5 00219 529 6 00004 611 6 00076 600 6 00089 610 7 00124 720 7 00254 721 7 00270 735 7 00281 720 7 00284 720 7 00286 720 7 00287 721 7 00289 720 7 00292 720 7 00350 720 7 00392 720 VALUE PHONO PLUG 1 72X1 4 1 72X5 32X3 64 6 32X13 16 4 40X1 2 M F 8 32X1 4PF GROMMET STRIP CLIP CABLE SWITCH 23 18 BLACK 23 18 RED 554808 1 3 18 13 18 8 32X3 8PF 5 PIN 18AWG OR INSL 4 PIN SIL 30 PIN DIL 3 PIN 18AWG OR 30 COND DIL 34 COND 5 PIN SI 5 PIN SIL 11 PIN 18AWG OR 14 26 IDC 40 CE 34 60 CE TO IDC 9418 20 COND DPDT ENA1J B20 SAS50B 130V 1200A 100K 56240 100P 010 2 SPKR TRANSCOVER2 MOD PLTFM 4 PLTFM 7 PLTFM 18 PLTFM 20 7 CRT SCREEN PLTFM 23 PLTFM 26 PLTFM 27 PLTFM 29 SR770 4 DESCRIPTION Hardware Misc Screw Slotted Nut Hex Standoff Standoff Screw Flathead Phillips Grommet Hardware Misc Hardware Misc Wire 18 UL1007 Stripped 3 8x3 8 No Tin Wire 18 UL1007 Stripped 3 8x3 8 No Tin Hardware Misc Wire 18 UL1015 Strip 3 8 x 3 8 No Tin Wire 18 UL1007 Stripped 3 8x3 8 No Tin Screw Black All Types Connector Amp MTA 156 Connector BNC Cable Assembly Ribbon Connector Male Connector Amp MTA 156 Cable Assembly Ribbon Cable Assembly Ribbon Connector Male Cable Assembly Ribbon Connector Amp MTA 156 Cable Assembly Custom Cable Assembly Custom Cable Assembly Multiconductor Cable Assembly Ri
43. 7 00147 720 7 00394 720 7 00395 720 7 00402 720 7 00405 720 VALUE 27C010 120 27C010 120 27C512 120 27 512 120 27 512 120 4 FAN GUARD RIGHT FOOT LEFT FOOT 6 32X3 8PP 4 40X1 4PP REAR FOOT 6 32X3 8TR PH 10 32X3 8TRUSSP 4 40X1 2 PP 6 32X7 16 PP BAIL SR770 6 SR770 7 SR770 8 SR770 11 DESCRIPTION Fabricated Part Printed Circuit Board Fabricated Part Fabricated Part Fabricated Part Fabricated Part Fabricated Part Fabricated Part Injection Molded Plastic Fabricated Part Fabricated Part Fabricated Part Machined Part Fabricated Part Printed Circuit Board Printed Circuit Board Fabricated Part Fabricated Part Fabricated Part Fabricated Part Keypad Conductive Rubber Lexan Overlay Fabricated Part Disk Drive CRT Display Product Labels DESCRIPTION EPROM PROM I C EPROM PROM I C EPROM PROM I C EPROM PROM I C EPROM PROM I C Tie Hardware Misc Hardware Misc Hardware Misc Screw Panhead Phillips Screw Panhead Phillips Hardware Misc Screw Truss Phillips Screw Black All Types Screw Panhead Phillips Screw Panhead Phillips Fabricated Part Fabricated Part Fabricated Part Fabricated Part Fabricated Part 7 30 eee PARTS LIST EMEN REF SRS PART VALUE DESCRIPTION 20 7 00408 720 SR770 14 Fabricated Part 7 31 EN PARTS LST 7 32
44. ANALYZER SAFETY AND PREPARATION FOR USE WARNING Dangerous voltages capable of causing injury or death are present in this instrument Use extreme caution whenever the instrument covers are removed Do not remove the covers while the unit is plugged into a live outlet CAUTION This instrument may be damaged if operated with the LINE VOLTAGE SELECTOR set for the wrong AC line voltage or if the wrong fuse is installed LINE VOLTAGE SELECTION The SR770 operates from a 100V 120V 220V or 240V nominal AC power source having a line frequency of 50 or 60 Hz Before connecting the power cord to a power source verify that the LINE VOLTAGE SELECTOR card located in the rear panel fuse holder is set so that the correct AC input voltage value is visible Conversion to other AC input voltages requires a change in the fuse holder voltage card position and fuse value Disconnect the power cord open the fuse holder cover door and rotate the fuse pull lever to remove the fuse Remove the small printed circuit board and select the operating voltage by orienting the printed circuit board so that the desired voltage is visible when pushed firmly into its slot Rotate the fuse pull lever back into its normal position and insert the correct fuse into the fuse holder LINE FUSE Verify that the correct line fuse is installed before connecting the line cord For 100V 120V use a 1 Amp fuse and for 220V 240V use a 1 2 Amp fuse LIN
45. ASCII form to the file specified by the FNAM command See the Store and Recall menu secion for more details on ASCII files The SVST command saves the analyzer settings to the file specified by the FNAM command The RCTR command recalls trace data display and measurement settings and scaling parameters from the file specified by the FNAM command to the active trace graph Data and limit tables are also recalled The RCST command recalls the analyzer settings from the file specified by the FNAM command 5 20 ee REMOTE PROGRAMMING TRACE MATH COMMANDS When using the math command COPR the status bytes should be queried after the command is sent to check if the command generated an error Common sources of errors are divide by zero math overflow and underflow For example the command line COPR ESR lt gt will perform an operation and return the Standard Event Status Byte when finished The Execution Error bit may be checked to make sure that the FITS command terminated without error CSEL 7 i The CSEL command sets or queries the type of math operation selected The parameter i selects the operation operation 0 4 2 x 3 4 5 log base 10 6 phase unwrap 7 d dx COPR i The COPR command starts the calculation selected by the CSEL command This may take some time Use status byte query to detect when the calculation is done Make sure that CARG and CONS have been used to set the argument value before u
46. Baud Rate for the plotter may be selected The baud rate is adjusted using the knob and must match the baud rate of the plotter Plotter Addr Plotter Addr If the Plot Mode is GPIB then the Plotter Address must be set The Plotter Address may be entered from the keypad or by using the knob The Plotter Address must agree with the address of the plotter in use SYSTEM MENU Plot Speed Define Pens Trace Pen Alpha Pen Marker Pen Return This key toggles the Plot Speed Normally when plotting on paper the Fast Plot Speed is used When plotting on transparencies or other nonstandard media the Slow plot speed may be better Many plotters have a multipen carousel In this case each part of the screen may be plotted using a different color pen The Define Pens key activates a submenu in which each feature of the screen may be assigned a pen number The allowable pen numbers are from 1 to 6 When using a single pen plotter all features are plotted using the one pen regardless of the pen definitions Trace This field assigns a pen number to the data trace on the screen Grid Pen This field assigns a pen number to the graph grid Alpha Pen This field assigns a pen number to all of the alphanumeric labels on the screen Marker Pen This field assigns a pen number to the dashed marker region lines and marker Return This key returns to the Setup Plotter menu The Return key will return to the ma
47. C 513 SRS PART 5 00197 501 5 00148 545 5 00148 545 5 00148 545 5 00148 545 5 00148 545 5 00148 545 5 00148 545 5 00148 545 5 00148 545 5 00100 517 5 00002 501 5 00100 517 5 00100 517 5 00100 517 5 00100 517 5 00100 517 5 00100 517 5 00100 517 5 00100 517 5 00023 529 5 00023 529 5 00100 517 5 00100 517 5 00023 529 5 00023 529 5 00023 529 5 00023 529 5 00219 529 5 00100 517 5 00219 529 5 00100 517 5 00219 529 5 00100 517 5 00219 529 5 00100 517 5 00219 529 5 00219 529 5 00100 517 5 00219 529 5 00219 529 5 00100 517 5 00219 529 5 00100 517 5 00219 529 5 00100 517 5 00172 544 5 00172 544 5 00023 529 5 00023 529 5 00100 517 VALUE 18P 1000P 1000P 1000P 1000P 1000P 1000P 1000P 1000P 1000P 2 2U 100P 2 2U 2 2U 2 2U 2 2U 2 2U 2 2U 2 2U 2 2U 2 20 2 20 010 2 20 010 2 20 010 2 20 010 2 20 010 DESCRIPTION Capacitor Ceramic Disc 50V 10 SL Capacitor Monolythic Ceramic COG 1 Capacitor Monolythic Ceramic COG 1 Capacitor Monolythic Ceramic COG 1 Capacitor Monolythic Ceramic COG 1 Capacitor Monolythic Ceramic COG 1 Capacitor Monolythic Ceramic COG 1 Capacitor Monolythic Ceramic COG 1 Capacitor Monolythic Ceramic COG 1 Capacitor Monolythic Ceramic COG 1 Capacitor Tantalum 35V 20 Rad Capacitor Ceramic Disc 50V 10 SL Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum
48. Error ROM Error A D Error DSP Error Overload usage Set when an error occurs during printing or plotting Set when an internal math error occurs Set when the RAM Memory test finds an error Set when an error occurs during a disk or file operation Set when the ROM Memory test finds an error Set when the A D test finds an error Set when the DSP test finds an error Set when the signal input exceeds the input range The Error Status bits stay set until cleared by reading or by the CLS command 5 30 ee REMOTE PROGRAMMING EXAMPLE PROGRAM 1 Using Microsoft C with the National Instruments GPIB card on the IBM PC To successfully interface the SR770 to a PC via the GPIB interface the instrument interface card and interface drivers must all be configured properly To configure the SR770 the GPIB address must be set in the SETUP menu The default GPIB address is 10 use this address unless a conflict occurs with other instruments in your system The SR770 will be set to GPIB address 10 whenever a reset is performed power on with the lt key down Make sure that you follow all the instructions for installing the GPIB card The National Instruments card cannot be simply unpacked and put into your computer To configure the card you must set jumpers and switches on the card to set the I O address and interrupt levels You must run the program IBCONF to configure the resident GPIB driver for you GPIB card Please ref
49. FUNCTIONS Display Measurements Analysis Trace Math Graphic Expand MARKER FUNCTIONS Harmonic Marker Delta Marker Next Peak Harmonic Data Tables Limit Tables SOURCE OUTPUT Amplitude Range Amplitude Resolution DC Offset Output Impedance SINE Amplitude Accuracy Frequency Resolution Harmonics Sub Harmonics Spurious Signals TWO TONE Amplitude Accuracy Frequency Resolution Harmonics Sub Harmonics Spurious Signals WHITE NOISE Flatness PINK NOISE Flatness CHIRP Flatness Phase GENERAL Monitor Real imaginary magnitude or phase spectrum Spectrum power spectral density time record and 1 3 octave Band sideband total harmonic distortion and trace math Add subtract multiply and divide with a constant 2zf or another trace Log base 10 square root phase unwrap and d dx functions Display expands up to 50x about any point in the display Displays up to 400 harmonics of the fundamental Reads amplitude and frequency relative to defined reference Locates nearest peak or harmonic to the left or right Lists Y values of up to 200 user defined X points Automatically detects data exceeding up to 100 user defined upper and lower limit trace segments 0 1 mVpk to 1 000 Vpk 1 mVpk Output gt 100 mVpk 0 1 mVpk Output x 100 0 mVpk 10 0 mV typical lt 5 50 mA peak output current 1 0 09 dB of setting O Hz to 100 kHz 0 1 Vpk to 1 0 Vpk high impedance load 15 26 mH
50. Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1W 1 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 7 18 eee PARTS LIST EMEN REF R 611 SO501 SO504 T 301 T 501 TP301 TP302 TP502 TP503 TP505 TP601 TP602 U 101 U 102 U 103 U 104 U 105 U 106 U 108 U 201 U 202 U 203 U 204 U 207 U 301 U 302 U 303 U 304 U 305 U 306 U 501 U 502 U 503 U 506 U 507 U 508 U 509 U 510 U 511 U 512 U 513 U 514 U 515 U 516 U 517 U 518 U 519 U 520 U 521 U 601 U 602 SRS PART 4 00086 401 1 00108 150 1 00026 150 6 00009 610 6 00137 601 1 00143 101 1 00143 101 1 00143 101 1 00143 10
51. Integrated Circuit Surface Mount Pkg STATIC RAM I C STATIC RAM I C STATIC RAM GAL PAL Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg STATIC RAM I C STATIC RAM I C Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Transistor TO 92 Package Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg nnn Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg 7 19 EN PARTS LST REF U 603 U 604 U 605 U 606 U 607 U 608 U 609 U 610 U 611 U 612 U 613 U 614 Z0 Analog Input Board Parts List REF C 101 C 102 C 103 C 104 C 105 C 106 C 107 C 108 C 109 C 110 C 111 C 112 C 113 C 118 C 202 C 250 C 251 C 252 C 253 C 256 C 259 C 260 C 261 C 262 C 263 C 264 C 265 C 266 C 268 C 269 C 270 C 271 C 272 C 273 SRS PART 3 0045
52. Linear i20 or Exponential i71 The OVLP command sets or queries the overlap percentage The OVLP x command sets the overlap to x percent The value of x ranges from 0 to 99 8 If the programmed value exceeds the maximum allowable overlap for the span the overlap will be set to the maximum allowed 5 15 REMOTE PROGRAMMING SOURCE COMMANDS STYP 2 i SLVL i 4 x SFRQ 2 Cf SCAL i APHS NTYP i The STYP command sets or queries the source type The parameter i selects Off 150 Sine i21 2 Tone i 2 Noise i 3 or Chirp i24 The configuration of each source may be set before the source is turned on The SLVL command sets or queries the source level The parameter i selects Sine 150 Tone 1 i21 Tone 2 i22 Noise i23 or Chirp i24 The parameter i is required The SLVL i x command sets source i level to x mV The SFRQ command sets or queries the source frequency The parameter i selects Sine i20 Tone 1 i21 Tone 2 i22 The parameter i is required The SFRQ i f command sets source i frequency to f Hz The SCAL command sets or queries the Source Cal mode for noise and chirp Sources The parameter i selects Source Cal Off 150 or On i21 This command only has an effect when the source type is noise or chirp Source Cal has NO effect unless the source is Chirp or Noise Do not select Source Cal On and use an external signal source The input calibrations are modif
53. Menu OPERATION Default Settings Front Panel 3 1 Power On Off 3 1 PROGRAMMING Reset 3 1 GPIB Communications Video Display 3 1 RS232 Communications Soft Keys 3 2 Status Indicators and Queues Keypad 3 2 Command Syntax Spin Knob 3 2 Interface Ready and Status Disk Drive 3 2 BNC Connectors 3 2 Detailed Command List Frequency Commands Screen Display 3 3 Measurement Commands Data Display 3 3 Display and Marker Commands Single Dual Trace Displays 3 3 Scale Commands Marker Display 3 5 Input Commands Menu Display 3 5 Analysis Commands Status Indicators 3 5 Data Table Commands Limit Table Commands Keypad 3 7 Averaging Commands Normal and Alternate Keys 3 7 Source Commands Menu Keys 3 7 Print and Plot Commands 5 02 02 09 2 02 2 09 2 62 wo 7777 7 7 CO O CO CO KO Co CO 62 02 QD o M cali di ca CIL QUII UI eM gt gt gt gt gt 2 gt System Setup Commands Store and Recall Commands Trace Math Commands Front Panel Control Commands Data Transfer Commands Interface Commands Status Reporting Commands Status Byte Definitions Serial Poll Status Byte Serial Polls Service Requests SRQ Standard Event Status Byte FFT Status Byte Error Status Byte Program Examples Microsoft C Nat l Instruments GPIB BASIC Nat l Instruments GPIB TESTING Introduction Preset Serial Number Firmware Revisio
54. Package Voltage Reg TO 220 TAB Package Heat Sinks Nut Kep 7 27 EN PARTS LST REF Z0 Z0 Z0 Z0 20 SRS PART 0 00209 021 0 00231 043 0 00243 003 0 00373 000 1 00087 131 VALUE 4 40X3 8PP 1 32 4 SHOULD TO 220 CARD EJECTOR 2 PIN JUMPER Chassis Assembly Parts List REF 20 20 20 20 20 20 SRS PART 0 00014 002 0 00043 01 1 0 00048 01 1 0 00079 031 0 00084 032 0 00089 033 0 00098 042 0 00108 054 0 00111 053 0 00112 053 0 001 16 050 0 00122 053 0 00123 053 0 00149 020 0 00168 023 0 00187 021 0 00190 030 0 00209 021 0 00210 020 0 00212 021 0 00231 043 0 00241 021 0 00248 026 0 00256 043 0 00257 000 0 00259 021 0 00310 010 0 00330 050 0 00331 031 0 00335 000 0 00336 027 0 00337 027 0 00338 023 0 00340 016 0 00343 027 0 00350 053 0 00368 053 0 00369 053 0 00372 000 0 00377 004 0 00378 004 0 00382 000 VALUE 6J4 4 40 KEP 6 32 KEP 4 40X3 16 M F 36154 4 6 LOCK 1 26 1 3 4 24B 1 3 4 24R 11 3 4 18 2 1 4 24 21 24 4 40X1 4PF 6 32X5 16R 4 40X1 4PP 8X1 4 40X3 8PP 4 40X5 16PF 6 32X2PP 1 32 4 SHOULD 4 40X3 16PP 10 32X3 8TRUSSP 6 SHOULDER HANDLES 4 40X1 2 PP HEX 3 8 32 5 1 2 18 4 40X5 8 F F FAN GUARD 2 4X1 4PP B 4X3 8PP B 2 56X1 4RP F0204 4X1 4PF B 2 1 4 24 21 24 21 24 CU FFT SR760 830 780 CAP 760 830 780 CARD GUIDE 4 5 DESCRIPTION Screw Panhead Phillips Washer nylon Insulators Hardware Misc Conn
55. Pressing ACTIVE TRACE toggles the active trace In the single trace display format the graph switches between 0 1 In the dual screen display ACTIVE TRACE switches which trace is active as indicated by the highlighted trace identification at the upper right of the graph In both cases the active trace determines which trace s parameters are displayed in the menus For example activating TraceO and then selecting the Measure menu will allow you to select the measurement for 13 0 Pressing ACTIVE TRACE once allows you to select the measurement for Trace1 using the same menu Only those parameters which are associated with an individual trace have differing values between the traces Parameters such as input configuration frequency span and window function are the same for any live trace AUTO RANGE Pressing AUTO RANGE toggles the input ranging mode between Manual and Auto In Manual mode the input range is set within the INPUT menu When the mode is toggled to Auto the input range is stepped quickly from 60 dB towards 30 dB until no overload is detected Any overload in the signal will cause the input scale to change to remove the overload If the signal decreases the input scale is not changed The range can be autoranged at any time by toggling the mode from Auto to Manual and back to Auto Switching back to Manual ranging leaves the input range at the current setting be inverse The Inp
56. THE CHIRP SOURCE Source triggering allows a stable phase curve to be measured at all spans Remember the source does not turn on sychronously with the input time record so the measured phase curve will be stable but with an arbitrary time delay Turn Auto Offset off in the INPUT menu to avoid interrupting the input and changing the absolute phases This key activates the chirp level entry field The output level is expressed in mV pk The level may be entered in either mV or dBV The knob always adjusts the level in mV The resolution is 1 mV for levels greater than 100 mV and 0 1 mV for levels less than 100 mV The peak output level is only approximate due to the ripple in the source output reconstruction filter The amplitude of each frequency component is roughly 32dB relative to the peak output If the individual frequency components were perfectly random then each component would be 1 0400 26 dB of the peak 4 56 een SOURCE MENU Auto Phase Source Cal Return However the chirp waveform is identical from time record to time record and each component has a fixed phase relative all the other components This reduces the amplitude of each component by another 6dB worsens the crest factor Thus the dynamic range of the measurement is reduced when using the chirp source This key performs the Auto Phase function When Source Triggering is on the measured phases of the frequency components of the chirp are
57. The alternate setup keys should only be used when accessing files on the disk drive or labelling plots SCALE Sets the graph scaling and expansion and selects linear or log MENU KEYS X axis All operating parameters of the SR770 are grouped ANALYZE Turns on harmonic sideband and into ten function menus The ten menu keys select band analysis as well as data and which menu of parameters is displayed next to the limit tables six soft keys The soft keys then either toggle a parameter highlight a parameter entry field for AVERAGE Tums averaging on and off and numeric entry or knob adjustment or display a selects the averaging type submenu The menus are listed below SOURCE Turns on and off and configures FREQ Sets the frequency span and start built in source and center frequencies SYSTEM Configures the computer interfa MEAS Displays submenus for selecting ces sound real time clock the measurement type displayed plotter printer screen 3 8 Mee OPERATION location The TEST submenu tests the keypad external keyboard knob RS232 interface printer interface disk drive video screen and memory The INFO submenu displays various information screens STORE RECALL This menu stores and recalls data and settings to and from the disk Also contains a disk utilities submenu Detailed descriptions of each menu are provided in a later chapter ENTRY KEYS The numeric entry keys can be used to
58. Wait indicator at the bottom of the screen 4 If the unit is being triggered check that the arming mode is set to AUTO If the arming mode is MANUAL then the analyzer will only trigger once and then wait for the next manual arming command 5 Check that the data is on scale by using AUTORANGE and AUTOSCALE 6 Make sure that the analyzer is not in the REMOTE state where the computer interfaces have locked out the front panel Press the LOCAL key the HELP key to restore local control If the analyzer still seems to function improperly turn the power off and turn it back on while holding down the lt backspace key This will reset the analyzer into the default configuration The analyzer should power on running and taking spectra 1 47 een ANALYZERBASICS WHAT IS AN FFT SPECTRUM ANALYZER The SR770 FFT Spectrum Analyzer takes a time varying input signal like you would see on an oscilloscope trace and computes its frequency spectrum Fourier s basic theorem states that any waveform in the time domain can be represented by the weighted sum of pure sine waves of all frequencies If the signal in the time domain as viewed on an oscilloscope is periodic then its spectrum is probably dominated by single frequency component What the spectrum analyzer does is represent the time domain signal by its component frequencies Why look at a signal s spectrum For one thing some measurements which are ve
59. and right using the Setup Screen function in the SYSTEM SETUP menu horizontal axis The graph is continuously updated while the unit is in the RUN mode A complete description of the screen display follows in the next section SOFT KEYS The SR770 has a menu driven user interface The 6 soft keys to the right of the video display have different functions depending upon the information displayed in the menu boxes at the right of the video display In general the soft keys have two uses The first is to toggle a feature on and off or to choose between settings The second is to highlight a parameter which is then changed using the spin knob or numeric keypad In both cases the soft keys affect the parameters which are displayed adjacent to them KEYPAD The keypad consists of five groups of keys The ENTRY keys are used to enter numeric parameters which have been highlighted by a soft key The MENU keys select a menu of soft keys Pressing a menu key will change the menu boxes which are displayed next to the soft keys Each menu presents a group of similar parameters and functions The CONTROL keys start and stop actual data acquisition select the marker and toggle the active trace These keys are not in a menu since they are used frequently and while displaying any menu The SYSTEM keys print the screen to a printer and display help messages Once again these keys can be accessed from any menu The MARKER keys determine the marke
60. are not shown do not figure in the autoscaling calculations This key is identical to the AUTO SCALE key The Expand X key allows the active trace graph to be expanded and translated in the X axis This key activates knob control of translation the left icon and expand the right icon Graph expansion is a convenient way of examining closely spaced details of a spectrum without decreasing the span and increasing the acquisition time Horizontal expansion displays 128 64 30 15 or 8 bins across the graph Expansion is about the marker position unless the marker is too close the edge of the span In this case expansion leaves one edge of the graph fixed Whenever a graph is expanded the Expand at the bottom right of the graph is on Horizontal translation is in increments of one bin No graphical expansion is allowed when the X axis is logarithmic This key selects the X axis scaling for the active trace Linear graphs are the normal display for spectrum analyzers The logarithmic graph is convenient for certain types of filter or broadband noise measurements The number of frequency bins displayed is always 400 and they are linearly spaced The log axis merely displays these points differently The first displayed point of a baseband span one that starts at DC is the frequency of the first bin not DC or 0 Hz 4 28 en ANALYZE MENU EHI Analyze Harmonic Sideband None Harmonic Sideband The Analyze menu turn
61. around the largest data point on the graph The marker should now be on the 1 kHz signal The marker readout above the graph displays the frequency and amplitude of the signal The MARKER MAXMIN key can also be configured to search for the minimum point on the graph Pressing the MARKER MAX MIN key also selects the knob to adjust the marker position The Span Menu box becomes unhighlighted A box is drawn around the marker readout to indicate that the knob will move the marker een GETTING STARTED EN 12 Decrease the span to 1 56 kHz using the Span key and knob the SPAN DOWN key or by entering the span numerically Press MARKER MAX MIN Press MARKER CENTER Decrease the span to 97 5 Hz using the Span key and knob the SPAN DOWN key or by entering the span numerically Press MARKER MAX MIN Press AUTO SCALE Press ANALYZE Press lt Harmonic gt Press lt Next Harmonic Right gt 1 3 This isolates the 1 kHz fundamental frequency Move the marker to the peak at 1 kHz This sets the span center frequency to the marker frequency The signal will be at the center of the span Further adjustments to the span will keep the center frequency fixed You may notice that the spectrum takes a while to settle down at this last span This is because the frequency resolution is 1 400 of the span or 244 mHz This resolution requires least 4 096 seconds of time data Note that the Settling
62. as the Soft Key or simply the Soft Key 1 23 The Measurement This measurement is designed to familiarize the user with the limit tables We will use the SR770 Source to provide a test signal so that there is some data to test Specifically you will generate a limit table to test the signal level as well as the noise floor ENN GETTING STARTED LIMIT TABLES 1 the analyzer on while holding down the lt backspace key Wait until the power on tests are completed 2 Connect the SR770 Source output to the A input Press SOURCE Press lt Sine gt 3 Press AUTO RANGE 4 Press SPAN DOWN until the span is 6 25 kHz 5 Press AUTO SCALE 6 Press ANALYZE Press Limit Table 7 Press MARKER MAX MIN 8 Press X Values Press 9 0 0 Hz Press X Values again Press 1 1 kHz When the power is turned on with the backspace key depressed the analyzer returns to its default settings See the Default Settings list in the Menu section for a complete listing of the settings Display the Source menu Turn on the Sine output Leave the sine frequency and level at the default settings 1 kHz and 1 Vpk Let the analyzer automatically set its input range Set the span to display the 1 kHz signal and its first few harmonics Set the graph scaling to display the entire range of the data Display the Analysis menu Select Limit Table display The display swi
63. auto binary dump mode will be turned off 5 24 en REMOTE PROGRAMMING INTERFACE COMMANDS RST IDN LOCL 7 i OVRM 2 i The RST command resets the SR770 to its default configurations The communications setup is not changed All other modes and settings are set to their default conditions and values This command takes some time to complete The IDN query returns the SR770 s device identification string This string is in the format Stanford_Research_Systems SR770 s n00001 ver007 In this example the serial number is 00001 and the firmware version is 007 The LOCL command sets the RS232 local remote function If 0 the SR770 is LOCAL if i 1 the SR770 will go REMOTE and if i 2 the SR770 will go into LOCAL LOCKOUT state The states duplicate the GPIB local remote states In the LOCAL state both command execution and keyboard input are allowed In the REMOTE state command execution is allowed but the keyboard and knob are locked out except for the HELP key which returns the SR770 to the LOCAL state In the LOCAL LOCKOUT state all front panel operation is locked out including the HELP key The OVRM command sets or queries the GPIB Overide Remote Yes No condition The parameter i selects No i 0 or Yes i21 When Overide Remote is set to Yes then the front panel is not locked out when the unit is in the REMOTE state 5 25 REMOTE PROGRAMMING STATUS REPORTING COMMANDS The Status By
64. be confugured before using the PRSC command The ACTG command sets or queries the active trace number The parameter i selects TraceO i 0 or Trace1 i21 This is similar to the ACTIVE TRACE key The ARNG command sets or queries the ranging mode The parameter i selects Manual i20 or Auto i21 This is similar to the AUTO RANGE key If i 1 and autorange is already on a new autorange is performed The AUTS command performs the Auto Scale function on trace g This function is the same as pressing the AUTO SCALE key when trace g is active The AUTS command affects the TREF BREF and YDIV parameters below 5 22 ee REMOTE PROGRAMMING DATA TRANSFER COMMANDS SPEC g i BVAL g i SPEB g The SPEC command reads the trace data in ASCII format from trace g If the parameter i is included only the value of the data in bin i is returned The first bin is i 0 and the last bin is i 399 0 O 10 14 for 15 band octave analysis and 00 is omitted then the entire trace is returned In this case data is sent continuously starting with bin 0 and ending with the bin 399 bin 14 or bin 29 for 15 or 30 band octave analysis Each data point is separated by a comma and the last data point is followed by a line feed GPIB or carriage return RS232 This format is convenient when using DMA driven host interfaces The data points are real numbers If SPEC is used to transfer the entire record over the RS232 interface the h
65. between settings The second is to highlight a parameter which is then changed using the knob or numeric keypad In both cases the softkey affects the parameter which is displayed adjacent to it Knob The knob is used to adjust parameters which have been highlighted using the softkeys Most numeric entry fields may be adjusted with the knob In addition functions such as display zooming and scrolling use the knob as well In these cases the knob function is selected by the softkeys The MARKER key which can be pressed at any time will set the knob function to scrolling the marker Example Measurement This measurement is designed to investigate the spectrum of a 1 kHz sine wave You will need a function generator capable of providing a 1 kHz sine wave at a level of 100 mV to 1 V such as the SRS DS345 The actual settings of the generator are not important since you will be using the SR770 to measure and analyze its output Choose a generator which has some distortion at least 70 dBc or use a square or triangle wave Specifically you will measure the spectrum of the sine wave measure its frequency and measure its harmonic distortion ENN GETTING STARTED M ANALYZING A SINE WAVE 1 the analyzer on while holding down the lt backspace key Wait until the power on tests are completed 2 Turn on the generator set the frequency to 1 kHz and the amplitude to approximately 1 Vrms Connect the generator s
66. directly enter parameter values Parameters may be entered only if their menu box is displayed and their entry field is highlighted For example if the FREQ menu is displayed the fifth soft key is next to the Start Freq box Pressing this soft key will highlight the entry field displaying the start frequency The menu box will appear as below Start Freq A new start frequency may now be entered using the numeric keys For example to set the start to 1 25 kHz press 1 2 5 As soon as the 1 is pressed the entry parameter is displayed in the upper left hand corner of the screen as shown below Note that the frequency menu is also replaced with a units menu iin This menu shows the available units for the active entry field in this case mHz Hz or kHz The entry field displays the char acters as the keys are pressed The is the entry point If an error is made the backspace lt Escape 3 9 key will erase the last character Pressing the Escape soft key will abort the entry operation and leave the value unchanged When the entry string is correct press the kHz units soft key to change the start frequency to the new value Entries may be made in exponential form using the EXP key The entry above may be made by pressing 1 2 5 EXP 1 and then the Hz units Soft key In general whenever a parameter entry field is highlighted the knob may also be used to adjust the valu
67. eee PARTS LIST EMEN REF R 270 R 271 R 272 R 301 R 303 R 304 R 305 R 306 R 307 R 308 R 309 R 310 R 311 R 312 R 313 314 315 R 316 317 R 318 R 319 320 321 322 323 324 325 326 327 R 328 329 350 351 352 353 354 355 356 357 358 359 R 360 361 362 363 364 365 366 367 368 402 SRS PART 4 00030 401 4 00030 401 4 00030 401 4 00162 407 4 00745 407 4 00417 407 4 00188 407 4 00188 407 4 00475 407 4 00235 407 4 00351 407 4 00188 407 4 00188 407 4 00348 407 4 00414 407 4 00601 407 4 00188 407 4 00188 407 4 00746 407 4 00747 407 4 00700 407 4 00188 407 4 00188 407 4 00655 407 4 00742 407 4 00188 407 4 00130 407 4 00048 401 4 00164 407 4 00161 407 4 00130 407 4 00030 401 4 00030 401 4 00030 401 4 00030 401 4 00030 401 4 00030 401 4 00030 401 4 00030 401 4 00141 407 4 00141 407 4 00030 401 4 00030 401 4 00141 407 4 00141 407 4 00141 407 4 00130 407 4 00136 407 4 00111 402 4 00111 402 4 00041 401 VALUE 10 DESCRIPTION Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resis
68. for the active trace This key chooses units of dBVolts RMS or dBEngineering Units RMS for the active trace dB units are not available when displaying Real or Imaginary parts of the spectrum This is because the data values may be negative This key chooses whether the fundamental unit is Volts or user defined Engineering Units EU Choosing EU will activate the EU definition menu shown below 4 9 MEASURE MENU M EU Label Pressing this key activates the EU Label entry field Use the ALT keys to enter EU Label a name for the engineering units EU Volt Pressing this key activates the EU scaling entry field Enter the number of EUVolt engineering units per Volt Return This key returns to the Units sub menu Return When Phase is being displayed on the active trace the Units menu appears as shown to the left Phase values are always between 180 and 180 degrees The analyzer does not unwrap phase The phase of a particular frequency bin is set to zero if neither the real nor imaginary part of the FFT is greater than 0 012 of full scale 78 dB below f s This avoids the messy phase display associated with the noise floor Remember even if a signal is small its phase extends over the full 360 degrees Return Degs This key chooses degrees for the Phase display Rads This key chooses radians for the Phase display Return The Return key will return to the main MEAS menu Note The choice of units
69. in this memory may be graphed on the screen 4 of the 7 80C186 s peripheral chip select strobes are used by peripherals on the CPU board PCSO is decoded into 16 I O strobes which access the clock keypad keyboard knob printer port etc PCS1 decodes the disk controller the GPIB controller and DMA acknowledge strobes PCS2 7 2 selects the UART and PCS3 selects the video graphics controller Whenever the video controller is accessed the ARDY line is asserted U504A which puts the processor into a wait state When the video controller acknowledges the data transfer by pulling Video_Rdy low the ARDY line is de asserted U805A and U815D and the processor moves on to the next instruction Interrupts generated by peripherals on the CPU board are combined in 0505 into single prioritized interrupt The highest priority pending interrupt will be encoded on U505 s outputs and read via the status port 0608 The UART directly interrupts the processor since it can never be masked KEYPAD INTERFACE The keypad is organized as 8 columns and 8 rows of switch closures The conductive rubber keys provide the switch closures 0607 strobes the columns and U606 detects the switch closure The diodes D601 D608 prevent one column from affecting another All of the outputs from U607 are set high and U606 is read periodically by the processor As long as OOH is read no key is pressed and the strobes are left on When a non zero byte
70. is read then the key strobes are activated individually in order to decode which key is down KEYBOARD INTERFACE The PC keyboard interface uses U603 to convert serial data from the keyboard into a parallel byte for the processor to read The data format from the keyboard is a leading start bit followed by 8 data bits U603 is reset by a processor read When a key is pressed the bits are shifted into U603 When the start bit appears at the QH output 7 bits of the data byte are 0603 0601 is the 9th bit of the shift register When U601 clocks in the start bit U601 must have the 8 bits of the data U601 then latches the serial data in U601 and interrupts the processor Only keyboards which operate in the PC or 8088 mode will function with this interface CIRCUIT DESCRIPTION SPIN KNOB The knob is an optical encoder buffered by U612 Each transition of its outputs is clocked into U610 or U611 and generates an interrupt at the output of U602A The processor keeps track of the knob s position continuously SPEAKER The speaker is driven by a timer on the 80C186 The timer outputs a square wave which is enabled by U602B and drives the speaker through Q705 CLOCK CALENDAR U702 is an MC146818 real time clock chip which keeps track of time and date The time base is a 32 768 kHz oscillator made by U706 Both U702 and U706 are battery backed up PRINTER INTERFACE The printer interface allows screen displa
71. is ready to receive it If either buffer overflows both buffers are cleared and an error reported The present value of a particular parameter may be determined by querying the SR770 for its value A query is formed by appending a question mark to the command mnemonic and omitting the desired parameter from the command Values returned by the SR770 are sent as a string of ASCII characters terminated by a carriage return lt cr gt on RS232 and by a line feed lt f gt on GPIB If multiple REMOTE PROGRAMMING queries are sent on one command line separated by semicolons of course the answers will be returned individually each with a terminator Examples of Command Formats TRSL O lt if gt CTRF 10 If Set trigger slope to positive Set the center frequency to 10000 Hz 10 kHz IDN If Queries the device identifica tion STRT If Starts data acquisition same as START key DISP 1 lt gt Queries the display type of the active trace INTERFACE READY AND STATUS The Interface Ready bit in the Serial Poll Status Byte signals that the SR770 is ready to receive and execute a command When a command is received this bit is cleared indicating that an operation is in progress While the operation is in progress no other commands will be processed Commands received during this time are stored in the buffer to be processed later Only GPIB serial polling will generate a response while a command is
72. key activates the File Name entry field File names are entered using the keypad and alternate keypad The ALT key allows letters to be entered DOS file name conventions must be followed i e file names are 8 characters or less with an extension of up to characters ABCDEFGH XYZ is a valid file name DOS sub directories are not supported All files are read from the root directory This key toggles the file catalog display screen on and off The use of this key is identical to the Catalog On Off function in the Save Data submenu describe previously The Return key will return to the main Store Recall menu Return also removes the catalog display screen and restores 4 81 ENN STORE RECALL MENU ee Recall Settings The Recall Settings submenu is used to recall the analyzer settings from a disk file The settings include all parameters which are set with the menus Recall Recall Settings Settings File Name File Name Catalog On Off Catalog On Return Pressing this key will read the settings information from the file specified in the File Name field This key activates the File Name entry field File names are entered using the keypad and alternate keypad The ALT key allows letters to be entered DOS file name conventions must be followed i e file names are 8 characters or less with an extension of up to characters ABCDEFGH XYZ is a valid file name DOS sub directories are not supported All files a
73. key copies the marker frequency into this field even when it is not activated When this field is activated knob adjustments and numeric entry are permitted Note that marker entries and knob adjustments are done with the resolution of the current frequency span For increased precision enter the frequency numerically 4 35 ANALYZE MENU Se Band Width Return This key activates the bandwidth entry field When this field is activated knob adjustments and numeric entry are permitted Note that knob adjustments are done with the resolution of the current frequency span For increased precision enter the frequency numerically This key returns to the main Analyze menu 4 36 ANALYZE MENU Data Table The data table reports the Y values for user entered X locations For example the entries could be a set of harmonic frequencies which need to be monitored To generate a report of the measurement the active trace s data table may be printed out using the Plot menu Each trace has its own data table though only the table associated with the active trace is active and displayed at any time To remove the data table display change the Format in the Display menu back to Single Table Index ANALYZE Table Mode Table Index Insert Item m Delete I3 Delete Table Return Note If no data table is entered or the data table has been deleted and harmonic or sideband anal
74. limits menu Set the audio alarm on Now whenever a trace is taken that exceeds the limit an alarm sounds Set the audio alarm off You re probably ready to turn off the alarms by now anyway Go back to the main limits menu Highlight the upper Y values menu field Enter a value higher than the signal peak Highlight the lower Y values menu field Enter a value higher than the signal peak The limit segment is now entirely above the signal peak and the PASS indicator is on at the bottom of the screen Remember this segment is an upper limit Let s add another segment to this table Highlight the Table Index menu box Entering an index or line number beyond the end of the table adds a new line to the end Notice how the new segment is a continuation of the previous one This makes building a continuous limit much simpler The starting point of the new line equals the ending point of the previous one 1 25 ENN GETTING STARTED M 12 13 14 15 14 Press Values gt until the upper field is highlighted Press 2 2 lt kHz gt Press lt X Values gt Press 2 8 lt kHz gt Press lt YValues gt until the upper field is highlighted Press 9 0 lt Enter gt Press lt Y Values gt Press 9 0 lt Enter gt Press lt Limit Type gt Press lt More gt Press lt Testing gt Press DISPLAY Press lt Format gt The new segment s length along the X axis is
75. message The alarm messages may be displayed for a variable length of time Enter a number from 1 shortest length to 10 longest length The Return key will return to the main System Setup menu 4 63 SYSTEM MENU Setup Time The Setup Time key activates the clock calendar sub menu The time and date Time E 45 12 Date 103 15 91 are used to label all screen prints and plots as well as disk files This menu is used to check or change the time and date SYSTEM Return Return Time The time is displayed as hours minutes seconds A 24 hour format is used This key toggles the entry field from hours to minutes to seconds A new entry may be made using the keypad or knob From the keypad the clock is set when the Enter softkey is pressed When the knob is used the clock is set whenever the highlighted value is changed Date The date is displayed as month day year This key toggles the entry field from months to days to years A new entry may be made using the keypad or knob From the keypad the calendar is set when the Enter Softkey is pressed When the knob is used the calendar is set whenever the highlighted value is changed Return The Return key will return to the main System Setup menu 4 64 en SYSTEM MENU EN Plot Plot All Plot Trace Plot Marker Title Today s Data Subtitle S Setu Plotter Plot All Plot Trace Plot Marker
76. most window functions are zero at the start and end of the time record Thus the points at the ends of the time record do not contribute much to the FFT With overlap these points are re used and appear as middle points in other time records This is why overlap speeds up averaging and smoothes out window variations Typically time records with 5096 overlap provide as much noise reduction as non overlapping time records when RMS averaging When RMS averaging narrow spans this can reduce the measurement time by a factor of 2 The maximum overlap is determined by the amount of time it takes to calculate an FFT and the length of the time record and thus varies according to the span 4 47 AVERAGE MENU The SR770 always tries to use the maximum amount of overlap possible Whenever a new frequency span is selected the overlap is set to the maximum possible value for that span If less overlap is desired then use this key to program in a smaller value On the widest spans 25 50 and 100 kHz no overlap is allowed If the measurement is triggered then overlap is ignored Time records start with the trigger The analyzer must be in continuous trigger mode to use overlap processing 4 48 een AVERAGE MENU BN 4 49 SOURCE M Source Configur Source Source Off Sine 2 Tone Noise The Source menu selects source output waveform The configure source menu sets the source parameters such a
77. multiple of the linewidth The keypad allows random frequencies to be entered The fundamental frequency resolution of the sine source is 15 26 mHz 1 kHz 65536 The entered frequency will be rounded to the nearest multiple of 15 26 mHz Remember the output is periodic over the input time record only if the frequency is a multiple of the linewidth Source triggering will not result in a stable phase for random frequencies This key activates the sine level entry field The output level is expressed in mVpk The level may be entered in either mVpk or dBVpk The knob always adjusts the level in mVpk The resolution is 1 mV for levels greater than 100 mV and 0 1 mV for levels less than 100 mV This key returns the main source selection menu 4 52 een SOURCE MENU Configure 2 Tone Frequency 1 00 kHz Level 1 500 mv Frequency 2 1 00 kHz Level 2 500 mV Return Frequency 1 2 Level 1 2 Return The Configure 2 Tone submenu allows the frequencies and amplitudes of the tones to be set SOURCE These keys activate the frequency entry fields for tones 1 and 2 When the knob is used to adjust the frequency the resolution is equal to the linewidth of the measurement span The knob always sets the tone frequency to an exact multiple of the linewidth The keypad allows random frequencies to be entered The fundamental frequency resolution of the tone is 15 26 mHz 1 kHz 65536 The en
78. of 1 3 of an octave 21 3 The octave analysis spectra will closely resemble data taken with older analog type equipment commonly used acoustics and sound measurement To compute the amplitude of each band the normal FFT is taken Those bins which fall within a single band are rms summed together square root of the sum of the squared magnitudes The resulting amplitudes are real quantities and have no phase information They represent total signal amplitude within each band We will have more about octave analysis later een ANALYZERBASICS DISPLAY TYPES Spectrum The most common measurement is the spectrum and the most useful display is the Log Magnitude The Log Mag display graphs the magnitude of the spectrum on a logarithmic scale using dBV as units Why is the Log Mag display useful Remember that the SR770 has a dynamic range of 90 dB and a display resolution of 114 dB below full scale Imagine what something 0 0196 of full scale would look like on a linear scale If we wanted it to be 1 centimeter high on the graph the top of the graph would be 100 meters above the bottom It turns out that the log display is both easy to understand and shows features which have very different amplitudes clearly Of course the analyzer is capable of showing the magnitude on a linear scale if you wish The real and imaginary parts are always displayed on a linear scale This avoids the problem of taking the log of negative
79. output to the A input of the analyzer 3 Press AUTO RANGE 4 Press the lt Span gt softkey to highlight the span Use the knob to adjust the span to 6 25 kHz You can also use the SPAN UP and SPAN DOWN keys to adjust the span 5 Press MARKER MAX MIN 6 Use the knob to move the marker around Take a look at some of the harmonics 7 Let s measure the frequency exactly 1 2 When the power is turned on with the backspace key depressed the analyzer returns to its default settings See the Default Settings list in the Menu section for a complete listing of the settings The input impedance of the analyzer is 1 The generator may require terminator generators have either a 50 1 or 600 O output impedance Use the appropriate feedthrough termination if necessary In general not using a terminator means that the output amplitude will not agree with the generator setting and the distortion may be greater than normal Since the signal amplitude may not be set accurately let the analyzer automatically set its input range to agree with the actual generator signal Note that the range readout at the bottom of the screen is displayed in inverse when the autoranging is on Set the span to display the 1 kHz signal and its first few harmonics You can also use the numeric keypad to enter the span In this case the span will be rounded to the next largest allowable span This centers the marker region
80. phase within each time record the absolute phase of the signal is arbitrary This is because the SR770 does not turn on and off the source synchronously with the FFT Go back to the Source menu Display the Sine frequency and level Select the frequency Set the frequency to 10 1 kHz This is NOT an exact bin frequency Note that the signal peak is dramatically reduced This is the effect of vector averaging a non coherent signal The signal peak is restored to its correct value once the frequency is an exact bin frequency again Go back to the Average menu Turn averaging off Display the Measure menu Choose the Window menu Windowing is used to turn a non periodic time record into a periodic one 1 35 ENN GETTING STARTED M Press MEAS Read Windowing in the Analyzer Basics section for more information In this case the source sine Press lt Window Menu gt is exactly periodic over a time record so windowing is not required The uniform window is no window at all The signal peak is unchanged in amplitude but has no frequency width This is because the signal is exactly on a frequency bin Press lt Uniform gt Note that this only works when the noise level is very low If the sine is noisy then windowing will still be required to achieve a clean spectrum Go back to the Source menu Display the Sine frequency and level 11 Press SOURCE Select the frequency Press lt Configure Source gt Set the frequ
81. selective window it selects a small range of frequencies around each bin However since the filter is narrow it falls off from center rapidly This means that even frequencies close to the bin may be attenuated somewhat If the filter is wide then frequencies far from the bin will contribute to the bin amplitude but those close by will probably not be attenuated much The net result of windowing is to reduce the amount of smearing in the spectrum from signals not exactly periodic with the time record The different types of windows trade off selectivity amplitude accuracy and noise floor The SR770 offers four types of window functions Uniform none Flattop Hanning and Blackman Harris BMH 2 6 Uniform The uniform window is actually no window at all The time record is used with no weighting A signal will appear as narrow as a single bin if its frequency is exactly equal to a frequency bin It is exactly periodic within the time record If its frequency is between bins it will affect every bin of the spectrum These two cases also have a great deal of amplitude variation between them up to 4 dB In general this window is only useful when looking at transients which do not fill the entire time record Hanning The Hanning window is the most commonly used window It has an amplitude variation of about 1 5dB for signals between bins and provides reasonable selectivity Its filter rolloff is particularly
82. starting band for octave analysis The starting band may be programmed from 2 O i O 30 subject to the limit that the starting band plus the number of bands 15 or 30 is less than 50 If the parameter i exceeds these limits then the value will be set to the maximum or minimum allowed value The WTNG command sets or queries the weighting function for octave analysis The parameter 0 selects no weighting and i21 selects A weighting 5 4 ee REMOTE PROGRAMMING 5 5 REMOTE PROGRAMMING MEASUREMENT COMMANDS When setting the trace type set the measurement first then the display type then the units This will change the trace type regardless of the previous settings This is because measurements take priority over the display type MEAS 2 i DISP g i UNIT g 6i VOEU 2 i EULB 2 05 EUVT 7 x WNDO 2 i The MEAS command sets or queries the measurement type for trace g The parameter i selects Spectrum i 0 PSD i 1 Time Record i 2 or Octave Analysis i 3 If the display type is incompatible with the new measurement then the display will be set to log magnitude The DISP command sets or queries the display type for trace g The parameter i selects Log Magnitude i 0 Linear Magnitude i 1 Real Part i 2 Imaginary Part i 3 or Phase i 4 Not all display types are available for all measurement types The table below lists which display types m
83. state to Off 0 or On 1 5 15 Set Query the Key Click to Off 0 or On 1 5 15 Set Query the Alarms to Off 0 or On 1 5 15 Set Query the Hours to 0 lt i lt 23 5 15 Set Query the Minutes to 0 lt i x 59 5 15 Set Query the Seconds to 0 x i x 59 5 15 Set Query the Month to 1 lt 1 lt 12 5 15 Set Query the Day to 1 lt 1 lt 31 5 15 Set Query the Year to 0 lt 1 lt 99 5 15 Set Query the Plotter Mode to RS232 0 or GPIB 1 5 15 Set Query the Plotter Baud Rate to 300 0 1200 1 2400 2 4800 3 oO lt lt gt gt gt gt A CO CO lt lt gt gt AA KO 9600 4 Set Query the Plotter GPIB Address to 0 x i lt 30 Set Query the Plot Speed to Fast 0 or Slow 1 Set Query the Trace Pen Number to 1 i lt 6 Set Query the Grid Pen Number to 1 i lt 6 Set Query the Alphanumeric Pen Number to 1 x i x 6 Set Query the Cursor Pen Number to 1 lt lt 6 Set Query the Printer Type to Epson 0 or HP 1 description Set Query the current File Name to string Save the Active Trace Data to the file specified by FNAM Save the Active Trace Data to the file specified by FNAM as an ASCII file Save the Settings to the file specified by FNAM Recall the Trace Data from the file specified by FNAM t
84. the frequency range allows The NHRT command moves the marker to the next harmonic to the right of the current marker position if it is on the graph If it is beyond the edge of the graph the span center frequency is set to the frequency of the next harmonic or as close as the frequency range allows The SBCA command sets or queries the sideband carrier frequency for trace g The parameter f is a real number of Hz The value of f can be programmed with more resolution than the span linewidth The SBSE command sets or queries the sideband separation frequency for trace g The parameter f is a real number of Hz The value of f can be programmed with more resolution than the span linewidth The NSBS command sets or queries the number of sidebands for trace g to i sidebands The parameter i can range from 0 to 200 The BSTR command sets or queries the band start frequency for trace g The parameter f is a real number of Hz The value of f can be programmed with more resolution than the span linewidth 5 12 en REMOTE PROGRAMMING BCTR g f BWTH 7 g f The BCTR command sets or queries the band center frequency for trace g The parameter f is a real number of Hz The value of f can be programmed with more resolution than the span linewidth The BWTH command sets or queries the band width for trace g The parameter f is a real number of Hz The value of f can be programmed with more resolution than the span linewidth
85. the power is turned off Remember that the values in the table do not have units associated with them An X location of 10 kHz is stored as 10 k and a Y value of 20 dBV is reported as simply 20 The Y values come directly from the graph so it is important to use the proper display units to get consistent data table readings There are two types of front panel keys which will be referenced in this section Hardkeys are those keys with labels printed on them Their function is determined by the label and does not change Hardkeys are referenced by brackets like this HARDKEY The softkeys are the six gray keys along the right edge of the screen Their function is labelled by a menu box displayed on the screen next to the key Softkey functions change depending upon the situation Softkeys will be referenced as the lt Soft Key gt or simply the Soft Key 1 20 The Measurement This measurement is designed to familiarize the user with the data tables We will use the SR770 Source to provide a test signal so that there is some data to report Specifically you will generate a data table to measure some harmonics as well as the noise floor eee GETTING STARTED EN DATA TABLES 1 Turn the analyzer on while holding down the lt backspace key Wait until the power on tests are completed 2 Connect the SR770 Source output to the A input Press SOURCE Press lt Sine gt 3 Press AUTO RANGE 4 Press SPAN DOWN
86. the table Wait for the Settling message at the bottom left corner of the screen to go out after changing the center frequency then press START AUTO SCALE MARKER MAX MIN b Record the marker Y reading for each center frequency 8 This completes the noise and spurious signal test Enter the results of this test in the test record at the end of this section 6 20 eee PERFORMANCE TESTS 11 Sine Source This test measures the source sine output Setup Connect the Source output to the A input Procedure 1 PRESET Turn the analyzer off wait a few seconds then back on with the lt key pressed 2 Press the keys in the following sequence SOURCE lt Sine gt AUTO RANGE MARKER MAX MIN 3 Record the marker Y reading 4 Press SOURCE lt Configure Source gt lt Level gt 2 0 lt dBV gt 5 Record the marker Y reading 6 Press 0 lt dBV gt 7 For each of the frequencies below perform steps 7a and 7b Frequency 10 kHz 20 kHz 40 kHz 60 kHz 80 kHz 99 kHz a Press lt Frequency gt Enter the frequency from the table MARKER MAX MIN b Record the marker Y reading 8 This completes the source sine test Enter the results of this test in the test record 6 21 PERFORMANCE TESTS 6 22 ee PERFORMANCE TESTS MEN SR770 Performance Test Record Serial Number Firmware Revision Equipment Used 1 Self Tests Test Power On Test Keypad
87. the table index can be used to scroll the window Entering an index will always display that line in the window for viewing or editing This key activates the X Value entry field The X value of the highlighted line may be entered using the numeric keypad No knob adjustment is allowed When this field is active the MARKER ENTRY key will copy the marker X position into this field This function inserts a new line before the highlighted line The new line becomes highlighted and is ready for editing 4 38 en ANALYZE MENU Delete Item This function deletes the highlighted line and highlights the following line Delete Table This function deletes the entire table Return This key returns to the main Analyze menu 4 39 ANALYZE MENU Limit Table The limit table lists the XY coordinates of the line segments which define the trace test limits When trace data exceeds these limit segments then the test fails To generate a listing of the active trace s limit table use the Print Limits function in the Plot menu Each trace has its own limit table though only the table associated with the active trace is active and displayed at any time To remove the limit table display change the Format in the Display menu back to Single Table Index ANALYZE Limit Table X Values 20 k 25 Y Values Table Index Limit Type per Lower Limit Type More A limit segment is defined as the line
88. this eliminates windowing effects and allows for source triggering and vector averaging Move the marker to the signal peak The marker picks the larger tone they should be just about equal This narrows the span and puts the center of the span on one of the tones 1 37 Press AVERAGE Press lt Number of Averages gt Press 2 0 lt Enter gt Press lt Average Mode to select Exponential Press lt Averaging gt to turn averaging on Press MARKER MAX MIN Press MARKER REF Use the knob to measure the distortion components GETTING STARTED M Display the Average menu Highlight the number of averages Enter 20 averages Select exponential averaging so that the display is live Turn averaging Notice how the noise floor has averaged to a stable value RMS averaging averages the magnitude of the signal and reduces the fluctuations in the data Note that distortion products may now be visible Intermodulation distortion IMD results in signal sidebands separated by the difference frequency In this case the two tones are at 9 and 10 kHz and the difference is 1 kHz Thus IMD products will show up at 8 7 kHz and 11 12 kHz Move the marker to the signal peak This turns on the marker offset and sets the reference marker to the current marker position From now on the marker will read relative to the signal peak A is displayed before the marker readout to indicate that t
89. this output filter s ripple The actual signal at the Source Output is not affected The output ripple is measured at the factory and is not adjustable by the user Source Cal only has an effect if the source is Noise or Chirp Source Cal can be turned off in the Configure Noise or Chirp menu Never select Noise or Chirp source with Source Cal On and use an external signal source The input calibrations are modified and will result in measurement errors unless the SR770 internal source is used as the test signal The amplitude of each frequency component is 1 43 ENN GETTING STARTED M 5 Press DISPLAY Press lt Format gt to select Up Dn Press ACTIVE TRACE to select the lower trace Press lt MEAS gt Press lt Display Menu gt Press lt Phase gt Press SOURCE Press lt Configure Source gt Press lt Auto Phase gt Press SPAN DOWN Press SPAN UP roughly 32dB relative to the peak output If the individual frequency components were perfectly random then each would be 1 0400 26 dB of the peak However the chirp source is deterministic and each frequency component has a fixed phase relative to all the other components This reduces the amplitude of each component by another 6dB worsens the crest factor Thus the dynamic range of the measurement is reduced when using the chirp source Go to the Display menu Display two traces The active trace has its trace identifier upper right of graph d
90. through an output reconstruction filter The Source Cal feature adjusts the input calibrations to compensate for this output filter s ripple The actual signal at the Source Output is not affected The output ripple is measured at the factory and is not adjustable by the user Source Cal only has an effect if the source is Noise or Chirp Source Cal can be turned off in the Configure Noise or Chirp menu Never select Noise or Chirp source with Source Cal On and use an external signal source The input calibrations are modified and will result measurement errors unless the SR770 internal source is used as the test signal Display the Measure menu Go to the Measure submenu Select Power Spectral Density Auto scale the graph The spectrum measures the amount of noise within a linewidth of each frequency bin Since the linewidth is simply 1 400th of the span the amount of noise signal in each bin will decrease with the span Power Spectral Density PSD normalizes all measurements to a 1 Hz bandwidth instead of the linewidth Since white noise is Gaussian it has a constant noise density 7 Measurements with the same bandwidth will yield the same noise level Thus PSD will measure the same noise at any span Move the marker Read the PSD at 50 kHz Remember this number Change the span to 25 kHz 1 40 eee GETTING STARTED EN Press SPAN DOWN twice to select a 25 kHz span Press FREQ Press Ce
91. varies from 1 to the of sidebands This key activates the carrier frequency entry field If no real time analysis was on when the sideband submenu was entered then this field is automatically filled with the marker frequency The Marker Entry key copies the marker frequency into this field even when it is not activated When this field is activated knob adjustments and numeric entry are permitted Note that marker entries and knob adjustments are done with the resolution of the current frequency span If the actual carrier is not exactly equal to a frequency bin then higher order sideband frequencies will be more and more inaccurate In this case enter the frequency numerically with as much precision as necessary The sideband frequency bins on the graph are identified by small triangle markers located at the Y positions of each sideband bin This is helpful in determining whether the carrier and separation frequencies are accurate enough to ensure that all sidebands are correctly identified This key activates the separation frequency entry field When this field is activated the knob adjusts the separation with the resolution of the current frequency span This resolution may lead to the higher order sideband frequencies being more and more inaccurate In this case enter the frequency numerically with as much precision as necessary 4 33 ANALYZE MENU Se Sidebands Return This key activates the of Sidebands entry fie
92. voltages The PSD and Octave analysis are real quantities and thus may only be displayed as magnitudes In addition the Octave analysis requires the display to be Log Magnitude Phase In general phase measurements are only used when the analyzer is triggered The phase is relative to the start of the time record 2 5 The phase is displayed in degrees or radians on a linear scale from 180 4 to 180 6 degrees rads There is no phase unwrap The phase of a particular frequency bin is set to zero if neither the real nor imaginary part of the FFT is greater than 0 012 of full scale 78 dB below fs This avoids the messy phase display associated with the noise floor Remember even if a signal is small its phase extends over the full 360 degrees Watch Out For Phase Errors The FFT can be thought of as 400 bandpass filters each centered on a frequency bin The signal within each filter shows up as the amplitude of each bin If a signal s frequency is between bins the filters act to attenuate the signal a little bit This results in a small amplitude error The phase error on the other hand can be quite large Because these filters are very steep and selective they introduce very large phase shifts for signals not exactly on a frequency bin On full span this is generally not a problem The bins are 250 Hz apart and most synthesized sources have no problem generating a signal right on a frequency bin But whe
93. we just saved Recalling the data from disk will restore the graph to what it was Display the Recall Data menu Display the disk catalog The 2 files which you just saved should be listed Pressing the MARKER key allows the knob to adjust the marker When the disk catalog is displayed the marker highlights a file Use the knob to choose a file to recall This recalls the data file from disk and displays it on the active graph Data acquisition is stopped so that the graph is not updated The file name is 1 16 ee GETTING STARTED EN 18 Press DISPLAY Press Format Press ACTIVE TRACE 19 Press START displayed below the graph The marker may be moved on the recalled graph to read specific data points The graph scaling may also be changed Show the Display menu Choose the Up Dn dual trace display format Make trace1 active the lower graph The active graph has a highlighted label at its upper right This restarts data acquisition but only for the active trace trace1 The recalled trace on 03 0 is still displayed To restart data acquisition on trace press ACTIVE TRACE to make 03 0 upper graph active and then START ENN GETTING STARTED M STORING AND RECALLING SETTINGS 1 Turn the analyzer on while holding down the lt backspace key Wait until the power on tests are completed Press SPAN DOWN a number of times to change the span Press INPUT Press lt Co
94. which define the trace test limits When trace data exceeds these limit segments then the test fails The limit table is a convenient way to test devices against a specification defined over a range of frequencies To generate a printed listing of a limit table use the Print Limits function in the Plot menu Each trace has its own limit table though only the table associated with the active trace is on and displayed at any time Limit tables are saved along with the trace data when data is saved to disk Limit tables are not stored in non volatile memory and are not retained when the power is turned off Remember that the values in the table do not have units associated with them An X location of 10 kHz is stored as 10 k and a Y value of 20 dBV is simply 20 The limit test compares the data on the graph in the display units to the Y values in the table It is important to use the correct units in the display to get consistent limit table tests There are two types of front panel keys which will be referenced in this section Hardkeys are those keys with labels printed on them Their function is determined by the label and does not change Hardkeys are referenced by brackets like this HARDKEY The softkeys are the six gray keys along the right edge of the screen Their function is labelled by a menu box displayed on the screen next to the key Softkey functions change depending upon the situation Softkeys will be referenced
95. will turn on the HI V indicator The input range is displayed in dBV The maximum and minimum range equivalents are tabulated below Max 34 dBVpk 31 dBVrms 50 1 Vpk 35 4 Vrms Min 60 dBVpk 63 dBVrms 1 0 mVpk 0 7 mVrms 2 9 Manual Range The input range can be specified in the Input menu to be fixed at a certain value Signals that exceed the range will overload and become distorted Signals which fall to a small percentage of the range will become hard to see Auto Range The input range can be set to automatically correct for signal overloads When autoranging is on and an overload occurs the input range is adjusted so that the signal no longer overloads If the signal decreases the input range is not adjusted You must take care to ensure that the signal does not fall dramatically after pushing the input range to a very insensitive setting While the analyzer is performing linear averaging the input range is NOT changed even if the signal overloads The overload indicator will still light to indicate an over range condition Changing the range during a linear average invalidates the average ANALYZER BASICS THE SOURCE The SR770 source provides a variety of test signals which allow the SR770 to measure the response of electronic mechanical and acoustic devices without the need for an external generator In many cases the SR770 source is better than an external source since it is synchronous with the inp
96. 0 Radial Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Cap Mini Electrolytic 25V 20 Radial Cap Monolythic Ceramic 50V 20 Z5U Cap Mini Electrolytic 25V 20 Radial Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 35V 20 Rad Cap Monolythic Ceramic 50V 20 Z5U Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Hardware Misc Hardware Misc Hardware Misc Hardware Misc Hardware Misc Relay Relay Relay Relay Relay 7 22 eee PARTS LIST EMEN REF K 106 K 107 L 501 N 501 N 502 N 503 P 101 P 102 P 103 P 104 P 301 PC1 Q 101 Q 102 Q 103 Q 104 Q 105 Q 106 Q 107 Q 501 R 101 R 102 R 103 R 104 R 105 R 106 R 107 R 108 R 109 R110 R111 R112 R113 R114 R115 R116 R117 R118 R119 R 120 R 121 R 122 R 123 R 124 R 125 R 126 R 127 R 128 R 129 R 130 R 131 SRS PART 3 00240 335 3 00
97. 0 use this address unless a conflict occurs with other instruments in your system The SR770 will be set to GPIB address 10 whenever a reset is performed power on with the lt key down Make sure that you follow all the instructions for installing the GPIB card The National Instruments card cannot be simply unpacked and put into your computer To configure the card you must set jumpers and switches on the card to set the I O address and interrupt levels You must run the program IBCONF to configure the resident GPIB driver for you GPIB card Please refer to the National Instruments manual for information In this example the following options must be set with IBCONF Device name fft770 Device address 10 EOS character OAH linefeed Terminate Read on EOS Yes Once all the hardware and GPIB drivers are configured use IBIC This terminal emulation program allows you to send commands to the SR770 directly from your computer s keyboard If you cannot talk to the SR770 via IBIC then your programs will not run Use the simple commands provided by National Instruments Use IBWRT and IBRD to write and read from the SR770 After you are familiar with these simple commands you can explore more complex programming commands 1 0 ER ERR ERE RR ER ERR ERE ERR KERR ERE KERR ER ERE ER ERR ER ERE ER ERE RR
98. 0136 171 1 00137 165 VALUE 74HC74 TAACTA 74HC164 74 299 63484 98 TAHC374 74HC374 32KX8 70L 32KX8 70L 74HC86 TAALSOA NAT9914BPD DS75160A DS75161A SCN2641 MC1488 DP8473AV 74HC157 24 000 MHZ 13 5168 MHZ 24 000 MHZ 3 6864 MHZ 3 1 2 24 1 5 X 30 ORA 26 COND 25 PIN IDC Power Supply Parts List REF C1 C2 C3 C4 C5 C7 C8 C9 C 10 C 11 C 12 C 13 C 16 C 17 C 18 C 19 C 20 C 21 C 23 C 24 SRS PART 5 00124 526 5 00124 526 5 00228 526 5 00228 526 5 00230 550 5 00229 521 5 00023 529 5 00127 524 5 00038 509 5 00027 503 5 00002 501 5 00027 503 5 00002 501 5 00127 524 5 00127 524 5 00127 524 5 00192 542 5 00127 524 5 00127 524 5 00192 542 5 00127 524 VALUE 5600U 5600U 15000U 15000U 47000U 15000U 220 100 010 100P 010 100P 2 2U 2 2U 2 2U 22U MIN 2 2U 2 2U 22U MIN 2 2U DESCRIPTION Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg STATIC RAM STATIC RAM I C Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Surface Mount Pkg Integrated Circ
99. 0dB 34dB 40dB 54dB and 6003 are realizable The resistive ladder attenuator provides attenuation from OdB to 12dB in 2 dB steps This improves the resolution with which gain can be selected At the output of the attenuator is U211 which detects overloads ANTI ALIASING FILTER To prevent aliasing the input signal passes through a low pass filter so that all frequency components greater than half the sampling frequency are attenuated by at least 96 dB This is accomplished with an 8 zero 9 pole elliptical low pass filter The pass band of this filter is DC to 100kHz with a ripple of 0 25 dB The stopband begins at 156 kHz Stopband attenuation is nominally 100 dB CIRCUIT DESCRIPTION The architecture of the filter is based on a singly terminated passive LC ladder filter L s simulated with active gyrators formed by op amp pairs Passive LC ladder filters have the special characteristic of being very tolerant of variations in component values Because no section of the ladder is completely isolated from the other a change in value of any single component affects the entire ladder The design of the LC ladder however is such that the characteristics of the rest of the ladder will shift to account for the change in such a way as to minimize its effect on the ladder Not only does this loosen the requirement for extremely high accuracy resistors and capacitors but it also makes the filter extremely stable d
100. 1 1 00143 101 1 00143 101 1 00143 101 3 00448 360 3 00366 341 3 00366 341 3 00366 341 3 00049 340 3 00476 343 3 00155 340 3 00448 360 3 00366 341 3 00366 341 3 00366 341 3 00472 343 3 00461 340 3 00364 340 3 00211 340 3 00238 340 3 00238 340 3 00238 340 3 00533 340 3 00366 341 3 00366 341 3 00531 340 3 00532 340 3 00130 340 3 00130 340 3 00130 340 3 00423 340 3 00130 340 3 01017 340 3 00383 340 3 00091 340 3 00116 325 3 00454 340 3 00440 340 3 00045 340 3 00371 340 3 00467 340 3 00440 340 3 00387 340 VALUE 51 PLCC 68 TH 28 PIN 600 MIL T1 1 X65 15MH TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK DSP56001 FE27 32KX8 35 32KX8 35 32KX8 35 74HC74 U106 74HC04 DSP56001 FE27 32KX8 35 32KX8 35 32KX8 35 U207 DSP2DEC OPA2604 TAF86 LT1016 74 74 74 74 74 74 ADSP2105 32KX8 35 32KX8 35 AD766JN 0744 5532 5532 5532 5534 5532 TLC7528CN LM6321 LF412 78L05 TAHC574 TAHC573 74HC32 DG444 T4HCT74 74HC573 74 245 DESCRIPTION Resistor Carbon Film 1 4W 5 Socket THRU HOLE Socket THRU HOLE Transformer Inductor Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Integrated Circuit Surface Mount Pkg STATIC RAM I C STATIC RAM I C STATIC RAM Integrated Circuit Thru hole Pkg GAL PAL Integrated Circuit Thru hole Pkg
101. 1 4W 5 7 25 EN PARTS LST REF R 403 R 501 R 502 R 503 R 504 R 505 R 506 R 507 R 508 R 509 R 510 R 511 R 512 50100 50101 505 101 TP102 TP103 TP201 TP202 TP203 TP204 TP205 TP206 TP301 TP302 TP303 TP401 TP402 TP403 TP404 TP405 TP406 TP407 TP408 TP501 TP502 TP503 TP504 TP505 TP506 TP507 TP508 TP511 TP512 TP513 TP514 TP515 TP516 TP517 SRS PART 4 00041 401 4 00169 407 4 00163 407 4 00163 407 4 00169 407 4 00107 402 4 00107 402 4 00107 402 4 00107 402 4 00112 402 4 00112 402 4 00042 401 4 00084 401 1 00173 150 1 00173 150 6 00009 610 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 1 00143 101 VALUE 150 249 2 80K 2 80K 249 5 1K 8 PIN MACH 8 PIN MACH T1 1 X65 TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST JACK TEST J
102. 213 U 301 U 302 U 303 U 304 U 305 U 306 U 307 U 308 U 309 U 401 U 501 U 504 U 505 U 506 U 507 U 509 U 510 U 511 U 512 U 513 U 514 U 515 U 516 U 517 U 518 U 519 Z0 Z0 SRS PART 1 00143 101 1 00143 101 1 00143 101 1 00143 101 3 00246 340 3 00817 340 3 00382 340 3 0047 1 340 3 00461 340 3 00087 340 3 0037 1 340 3 00155 340 3 00382 340 3 0037 1 340 3 00382 340 3 0037 1 340 3 00130 340 3 0037 1 340 3 0037 1 340 3 00423 340 3 00143 340 3 00037 340 3 00045 340 3 00130 340 3 00130 340 3 00130 340 3 00130 340 3 00423 340 3 001 16 325 3 00059 340 3 00091 340 3 00130 340 3 00392 340 3 00049 340 3 00265 340 3 00265 340 3 00265 340 3 00039 340 3 001 14 329 3 00120 329 3 00096 340 3 00100 340 3 001 16 325 3 00117 325 3 00116 325 3 00123 325 3 00122 325 3 001 12 329 3 00346 329 0 00012 007 0 00043 011 VALUE TEST JACK TEST JACK TEST JACK TEST JACK NPD5564 NPD5566 OP37 OP27GP OPA2604 LF347 DG444 74HC04 OP37 DG444 OP37 DG444 5532A DG444 DG444 5534 LM393 74HC138 74HC32 5532A 5532A 5532A 5532A 5534 78L05 7542 LF412 5532A PCM1750P 74HC74 74 595 74 595 74 595 74HC14 7815 7915 LM317L LM337L 78L05 78L12 78L05 79L12 79L05 7805 7812 TO 220 4 40 KEP DESCRIPTION Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Cir
103. 240 335 6 00055 630 4 00265 421 4 00265 421 4 00468 420 4 00354 445 4 00231 445 4 00730 445 4 00015 445 4 00016 445 7 00352 701 3 00021 325 3 00021 325 3 00021 325 3 00021 325 3 00021 325 3 00021 325 3 00021 325 3 00021 325 4 00616 453 4 00593 408 4 00259 408 4 00593 408 4 00259 408 4 00203 407 4 00580 407 4 00580 407 4 00544 407 4 00528 408 4 00528 408 4 00203 407 4 00138 407 4 00652 407 4 00652 407 4 00138 407 4 00217 408 4 00301 408 4 00142 407 4 00138 407 4 00652 407 4 00652 407 4 00138 407 4 00217 408 4 00234 407 4 00301 408 4 00142 407 4 00142 407 4 00234 407 4 00021 401 4 00192 407 VALUE BS 211 DC12 GF BS 211 DC12 GF FB43 1801 100X4 100X4 300X8 20 50K 100 100K 10K FFT ANALOG 2N3904 2N3904 2N3904 2N3904 2N3904 2N3904 2N3904 2N3904 49 9 965 0K 31 60K 965 0K 31 60K 75 0K 475 475 165 499 499 75 0K 10 0K 1 58K 1 58K 10 0K 1 000K 110 100K 10 0K 1 58K 1 58K 10 0K 1 000K 10 110 100K 100K 10 1 0K 49 9K DESCRIPTION Relay Relay Ferrite Beads Res Network SIP 1 4W 2 Isolated Res Network SIP 1 4W 2 Isolated Resistor Network DIP 1 4W 2 8 Ind Pot Multi Turn Side Adjust Pot Multi Turn Side Adjust Pot Multi Turn Side Adjust Pot Multi Turn Side Adjust Pot Multi Turn Side Adjust Printed Circuit Board Transistor TO 92 Package Transistor TO 92 Package Transistor TO 92 Package Transistor TO 92 Package Transistor TO 92 Pac
104. 3 5 00127 524 220 Capacitor Tantalum 50V 2096 Rad C 34 5 00127 524 2 20 Capacitor Tantalum 50V 2096 Rad D2 3 00391 301 MBR360 Diode D3 3 00391 301 MBR360 Diode D4 3 00391 301 MBR360 Diode D5 3 00391 301 MBR360 Diode D6 3 00391 301 MBR360 Diode D7 3 00391 301 MBR360 Diode D8 3 00391 301 MBR360 Diode D9 3 00391 301 MBR360 Diode D 12 3 00004 301 134148 Diode D 13 3 00004 301 134148 Diode D 15 3 00391 301 MBR360 Diode D 16 3 00001 301 1N4001 Diode D 17 3 00001 301 134001 Diode D 18 3 00001 301 134001 Diode D 19 3 00001 301 134001 Diode D 20 3 00001 301 134001 Diode D 30 3 00479 301 MUR410 Diode D 31 3 00479 301 MUR410 Diode D 32 3 00479 301 MUR410 Diode D 33 3 00479 301 MUR410 Diode D 34 3 00391 301 MBR360 Diode D 35 3 00391 301 MBR360 Diode D 36 3 00391 301 MBR360 Diode D 37 3 00391 301 MBR360 Diode D 38 3 00001 301 134001 Diode DS1 3 00011 303 RED LED T1 Package JP1 1 00039 116 5 PIN WHITE Header Amp MTA 156 JP2 1 00116 130 4 PIN DI DISK Connector Male JP3 1 00119 116 3 PIN WHITE Header Amp MTA 156 JP4 1 00171 130 34 PIN ELH Connector Male JP5 1 00086 130 3 PIN SI Connector Male JP6 1 00086 130 3 PIN SI Connector Male PC1 7 00354 701 4 Printed Circuit Board Q3 3 00021 325 2N3904 Transistor TO 92 Package Q4 3 00021 325 2N3904 Transistor TO 92 Package Q5 3 00257 329 41 Voltage Reg TO 220 TAB Package Q6 3 00378 329 102 Voltage Reg TO 220
105. 3 dBV 0 3 dBV 80 kHz 0 dBV 0 3 dBV 0 3 dBV 99 kHz 0 dBV 0 3 dBV 0 3 dBV 6 25 PERFORMANCE TESTS 6 26 PERFORMANCE TESTS 6 27 eee CIRCUIT DESCRIPTION Power Supply Board CPU Board DSP Logic Board Analog Input Board CAUTION Always disconnect the power cord and wait at least one minute before opening the unit Dangerous power supply voltages may be present even after the unit has been unplugged Check the LED at the front edge of the power supply board The unit is safe only if the LED is OFF If the LED is ON then DO NOT attempt any service on the unit This unit is to be serviced by qualified service personnel only There are no user serviceable parts inside 7 1 VIDEO DRIVER AND CRT Potentially lethal voltages are present in this circuit Do not attempt to service the CRT and Video Driver Board Refer any service problems to the factory CIRCUIT BOARDS The SR770 has four main printed circuit boards The four boards shown contain most of the active circuitry of the unit The CRT and video driver boards are mounted inside the CRT shield assembly A front panel circuit board only has keypad contacts printed on it and holds no active components CIRCUIT DESCRIPTION CPU BOARD The CPU board contains the microprocessor system All display front panel disk and computer interfaces are on this board MIC
106. 4 00193 407 4 00158 407 4 00409 408 4 00409 408 4 00746 407 4 00317 407 4 00652 407 4 00409 408 4 00409 408 4 00523 407 4 00177 407 4 00136 407 4 00048 401 4 00188 407 4 00161 407 4 00188 407 4 00654 407 4 00356 407 4 00031 401 4 00057 401 4 00782 448 4 00080 401 4 00080 401 4 00086 401 VALUE HS 2128 5 1 0KX4 100X7 100X7 300X8 100X3 100X3 FFT DIGITAL 2N3906 2N3906 4 7K 4 7K 10K 10K 10K 100K 10K 10 10 33 33 3 48K 66 5 2 80K 1 210K 1 210K 2 43K 499 2 00K 1 210K 1 210K 2 05K 422 1 58K 1 210K 1 210K 649 3 48K 1 82K 2 2K 4 99K 2 49K 4 99K 182 DESCRIPTION Relay Res Network SIP 1 4W 2 Isolated Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Resistor Network DIP 1 4W 2 8 Ind Res Network SIP 1 4W 2 Isolated Res Network SIP 1 4W 2 Isolated Printed Circuit Board Transistor TO 92 Package Transistor TO 92 Package Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 AW 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Comp 1 2W 5 Resistor Carbon Comp 1 2W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal
107. 4 340 3 00454 340 3 00475 343 6 00110 621 3 00364 340 3 00473 343 3 00474 343 3 00463 340 3 00117 325 3 00123 325 3 00190 340 6 00121 621 0 00373 000 SRS PART 5 00060 512 5 00060 512 5 00023 529 5 00100 517 5 00023 529 5 00159 501 5 00023 529 5 00100 517 5 00100 517 5 00100 517 5 00100 517 5 00100 517 5 00100 517 5 00225 548 5 00023 529 5 00023 529 5 00023 529 5 00023 529 5 00023 529 5 00023 529 5 00023 529 5 00023 529 5 00023 529 5 00023 529 5 00023 529 5 00023 529 5 00100 517 5 00100 517 5 00100 517 5 00100 517 5 00100 517 5 00100 517 5 00100 517 5 00100 517 VALUE 74HC574 74HC574 U605 PLTDECOD 30 208 MHZ TAF86 U608 COUNT118 U609 A ADCONTR TAF574 78L12 79L12 10MHZ 25PPM 27 000 MHZ CARD EJECTOR VALUE 1 0U 1 0U 220 6 8P 220 220 220 220 2 20 2 20 AXIAL 220 2 20 DESCRIPTION Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg GAL PAL Crystal Oscillator Integrated Circuit Thru hole Pkg GAL PAL GAL PAL Integrated Circuit Thru hole Pkg Transistor TO 92 Package Transistor TO 92 Package Integrated Circuit Thru hole Pkg Crystal Oscillator Hardware Misc DESCRIPTION Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 35V 20 Rad Cap Monolythic Ceramic 50V 20
108. 56 kHz To make sure that Nyquist s theorem is satisfied the input signal passes through an analog filter which attenuates frequency components above128 kHz by 90 dB This is the anti aliasing filler The resulting digital time record is then mathematically transformed into a frequency spectrum using an algorithm known as the Fast Fourier Transform or FFT The FFT is simply a clever set of operations which implements Fourier s basic theorem The resulting spectrum shows the frequency components of the input signal Now here s the interesting part The original digital time record comes from discrete samples taken at the sampling rate The corresponding FFT yields a spectrum with discrete frequency samples In fact the spectrum has half as many frequency points as there are time points Remember Nyquist s theorem Suppose that you take 1024 samples at 256 kHz It takes 4 ms to take this time record The FFT of this record yields 512 frequency points but over what frequency range The highest frequency will be determined by the period of 2 time samples or 128 kHz The lowest frequency is just the period of the entire record or 1 4 ms or 250 Hz Everything below 250 Hz is considered to be dc The output spectrum thus represents the frequency range from dc to 128 kHz with points every 250 Hz Advantages and limitations The advantage of this technique is its speed The entire spectrum takes only 4 ms to measure The limitation of th
109. 7 i g i MRKX g MRKY g MRPK MRCN MRRF MROF Ci The ACTG command sets or queries the active trace number The parameter i selects TraceO 150 or Trace1 i 1 The FMTS command sets or queries the display format The parameter i selects Single 150 or Up Dn i21 The GRID command sets or queries the grid on off condition for trace g The parameter i selects Off 150 8 i21 or 10 i22 divisions per screen The FILS command sets or queries the graph style for trace g The parameter i selects Line i 0 or Fill i1 The MRKR command sets or queries the marker on off track state for trace g The parameter i selects Off i20 On i21 or Track 122 The MRKW command sets or queries the marker width for trace g The parameter i selects Norm i 0 Wide i21 or Spot 22 The MRKM command sets or queries the marker seek mode for trace 9 If 0 the marker seeks the maximum if i 1 the marker seeks the minimum and if i 2 the marker seeks the mean The MRLK command sets or queries the marker linkage Off On state The parameter i selects Off 150 or On i21 The MBIN command moves the trace g marker region to bin i where 0 0 iQ 399 The marker region will be centered on bin i The marker will seek the max min or mean within the region as set by the marker seek mode The MRKX command queries the trace g marker X position The value returned is the same as the marker readout on the scree
110. ACK TEST JACK TEST JACK TEST JACK TEST JACK DESCRIPTION Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Comp 1 2W 5 Resistor Carbon Comp 1 2W 5 Resistor Carbon Comp 1 2W 5 Resistor Carbon Comp 1 2W 5 Resistor Carbon Comp 1 2W 5 Resistor Carbon Comp 1 2W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Socket THRU HOLE Socket THRU HOLE Transformer Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack Vertical Test Jack 7 26 eee PARTS LIST EMEN REF TP518 TP519 TP520 TP521 U 100 U 101 U 102 U 103 U 104 U 105 U 201 U 202 U 203 U 204 U 205 U 206 U 207 U 208 U 209 U 210 U 211 U 212 U
111. Averages gt Press 2 0 lt Enter gt Press lt Averaging gt Press MARKER Use the knob to move the marker to a region representative of the noise floor 1 8 ENN GETTING STARTED M the signal A is displayed before the marker readout to indicate that the reading is relative A small star symbol is located on the graph at the marker offset position The MARKER REF key automatically allows the knob to adjust the marker position The marker is now providing a direct reading of the signal to noise ratio Remember this is the S N for the source amplifier combination The MARKER REF key toggles the marker offset on and off We now want to turn the offset off Display the Measure menu Choose the Measurement type menu Select Power Spectral Density The PSD approximates the amplitude of the signal within a 1 Hz bandwidth located at each frequency bin This allows measurements taken with different linewidths spans to be compared To get a better measurement of noise a little averaging can help Display the Average menu Select Exponential averaging Highlight the Number of Averages menu box Enter 20 averages Turn averaging on Notice how the noise floor approaches a more stable value We are using RMS averaging to determine the actual noise floor See the section on Averaging for a discussion of the different types of averaging The MARKER key allows the knob to move the marker The M
112. C data latch U517 The ADSP 2105 computes the source waveforms a point every 4 us The output points are serially shifted to U506 a 16 bit serial input DAC The output frame sync is exactly the same as the input frame sync to the input A D converter Thus the source is synchronous with the input sampling The output of U506 is buffered and filtered to remove high frequency components U513A is used as an 8 bit attenuator and U502 is a divide by 10 or 100 attenuator U514 is a high current output buffer which provides the low output impedance ee CIRCUIT DESCRIPTION ANALOG INPUT BOARD OVERVIEW The Analog Input Board provides the very important link between the user s input signal and the DSP processor From the front panel BNC the user s signal passes through a low distortion front end amplifier gain stages attenuators anti aliasing filter and finally an A D Converter Once converted to digital form the input signal is ready to be processed by the Digital Signal Processors INPUT AMPLIFIER The goal of any measurement instrument is to perform some given measurement while affecting the quantities to be measured as little as possible As such the input amplifier is often the most critical stage in the entire signal path The design of the front end input amplifier in the SR770 was driven by an effort to provide optimum performance in the following areas input voltage noise input current noise input capacitance
113. Carbon Film 1 AW 5 Resistor Carbon Film 1 AW 5 Resistor Carbon Film 1 AW 5 Resistor Carbon Film 1 AW 5 Resistor Carbon Film 1 AW 5 Resistor Carbon Film 1 AW 5 Resistor Carbon Film 1 AW 5 Resistor Carbon Film 1 AW 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 AW 5 Resistor Carbon Film 1 AW 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 AW 5 Resistor Carbon Film 1 AW 5 Resistor Carbon Film 1 AW 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 AW 5 Resistor Carbon Film 1 AW 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 AW 5 Resistor Carbon Film 1 AW 5 Resistor Carbon Film 1 AW 5 7 11 EN PARTS LST REF SRS PART VALUE R 901 4 00273 401 5 6K R 904 4 00090 401 560 R 905 4 00090 401 560 R 911 4 00022 401 1 0M R 912 4 00062 401 270 R 913 4 00021 401 1 0K DESCRIPTION Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 50101 1 00108 150 PLCC 68 TH Socket THRU HOLE 0301 1 00156 150 32 PIN 600 MIL Socket THRU HOLE 0302 1 00156 150 32 PIN 600 MIL Socket THRU HOLE 50303 1 00156 150 32 PIN 600 MIL Socket THRU HOLE 50304 1 00156 150 32 PIN 600 MIL Socke
114. E CORD The SR770 has a detachable three wire power cord for connection to the power source and to a protective ground The exposed metal parts of the instrument are connected to the outlet ground to protect against electrical shock Always use an outlet which has a properly connected protective ground SERVICE Do not attempt to service or adjust this instrument unless another person capable of providing first aid or resuscitation is present Do not install substitute parts or perform any unauthorized modifications to this instrument Contact the factory for instructions on how to return the instrument for authorized service and adjustment 5 770 FFT SPECTRUM ANALYZER Symbols you may find on SRS products lt lt lt 2 pt o Jem 770 FFT SPECTRUM ANALYZER SPECIFICATIONS FREQUENCY Measurement Range Spans Center Frequency Accuracy Resolution Window Functions Real time Bandwidth SIGNAL INPUT Number of Channels Input Input Impedance Coupling CMRR Noise AMPLITUDE Full Scale Input Range Dynamic Range Harmonic Distortion Spurious Input Sampling Accuracy Averaging TRIGGER INPUT Modes Internal External External TTL Post Trigger Pre Trigger Phase Indeterminacy 476 wHz to 100 kHz baseband and zoomed 191 mHz to 100 kHz in a binary sequence Anywhere within the measurement range subject to span and range
115. EF Use the knob to measure the harmonic levels relative to the fundamental 18 Press MARKER REF 1 5 This moves the marker to the fundamental peak This sets the marker reference or offset to the frequency and amplitude of the fundamental The marker readout above the graph now reads relative to this offset This is indicated by the in front of the marker readout A small star shaped symbol is located at the screen location of the reference The MARKER REF key also allows the knob to move the marker The marker readout is now relative to the reference or fundamental level Pressing MARKER REF again removes the marker offset This concludes this measurement example You should have a good feeling for the basic operation of the menus knob and numeric entry and marker movement and measurements ENN GETTING STARTED M SECOND MEASUREMENT EXAMPLE This sample measurement is designed to further acquaint the user with the SR770 Network Analyzer Do not be concerned that your measurement does not exactly agree with this exercise The focus of this measurement exercise is to learn how to use the instrument There are two types of front panel keys which will be referenced in this section Hardkeys are those keys with labels printed on them Their function is determined by the label and does not change Hardkeys are referenced by brackets like this HARDKEY The softkeys are the six gray keys along the right edge
116. EN SYSTEM MENU 4 76 een STORE RECALL MENU Store Recall Save Data Settings Recall Data Settings Store Recall Keys The Store and Recall menu is used to save and recall data and settings to and from disk The Disk Utilities submenu can erase files and format blank disks Files are saved as DOS files and can be read by a DOS compatible computer with a 3 5 disk drive The file format is described in the Remote Programming section Note The SR770 uses double sided high density DS HD disks The maximum number of files allowed on a disk is 224 This is the DOS limitation on the number of directory entries in the root directory RECALL Recall Settings Disk Utilities Format Disk Catalog On Off Each softkey in this menu activates a submenu The submenus are described in detail on the following pages 4 77 Save Data ENN STORE RECALL MENU ee The Save Data submenu is used to save the active trace data and the associated limit and data tables The graph parameters frequency span measurement display units and window are all saved with the data Save Save Data Data I Save ASCII Data fm Save ASCII Data File Name TEST DAT Catalog File Name Return Pressing this key will save the active trace data and associated parameters to the file specified in the File Name field Pressing this key will save the act
117. ER MAX MIN Press MARKER REF Use the knob to move the marker to the signal harmonics Press MARKER REF Press INPUT Press Trigger Menu Press Trigger 4 times to select Source ENN GETTING STARTED M Generally the sine frequency should be an exact bin frequency this eliminates windowing effects and allows for source triggering and vector averaging Display the Averaging menu Highlight the number of averages Change the number of averages to 20 Select exponential averaging so the display is live Tum averaging on Notice how the noise floor has averaged to a stable value RMS averaging averages the magnitude of the signal and reduces the fluctuations in the data Note that harmonics may now be visible Move the marker to the signal peak at 10 kHz This turns on the marker offset and sets the reference marker to the current marker position From now on the marker will read relative to the signal peak A is displayed before the marker readout to indicate that the reading is relative A small star symbol is located on the graph at the marker offset position The ref marker gives a direct reading of the harmonic levels relative the fundamental Pressing MARKER REF again turns off the reference marker Display the Input menu Go to the Trigger menu Select Source Trigger This is a special trigger mode The spectra are taken with no overlap at all spans but without using the trigger circ
118. G STARTED Press 5 Volts Press AUTO SCALE Press MEAS Press Window Menu Press Uniform Press ACTIVE TRACE Press AUTO SCALE Press lt Hanning gt Press INPUT Press Trigger Menu Press Trigger Delay Press 2 5 6 Samples 0 5 V The upper trace should display the pulse waveform at the left edge Auto scale will set the display limits automatically Remember that we are displaying the magnitude of the signal Any negative portion of the signal will be folded back around zero and appear as a positive magnitude Because the pulse is much shorter than the time record we need to use the Uniform window The other window functions taper to zero at the start and end of the time record Always be aware of the effect windowing has on the FFT of the time record There should now be a spectrum on the lower trace Use AUTO SCALE to set the display The spectrum you see is the sinx x envelope of a rectangular pulse The zeroes in the spectrum occur at the harmonics of 1 pulse width 1 100us or 10 kHz Now choose the Hanning window Notice how the spectrum goes away We can get the spectrum back by delaying the time record relative to the trigger so that the pulse is positioned in the center of the time record Go back to the Trigger submenu Highlight the Trigger Delay menu box Enter 256 samples of delay Because the pulse repetition rate is 250 Hz the period between pulses
119. L PRINTER CONNECTOR The PRINT key will print the screen to an Epson compatible graphics printer or an HP LaserJet compatible laser printer Use a standard printer cable to attach the printer to the printer port Use the SETUP PRINTER menu to choose the type of printer PC KEYBOARD CONNECTOR An IBM PC or XT compatible keyboard may be attached to the keyboard connector An AT keyboard may be in its PC or 8088 mode Typing at the attached keyboard is the same as entering numbers and letters from the front panel keypad Highlighted parameter entry fields will accept characters from the keyboard Typing E or e is the same as EXP In general the keyboard is only useful for alphabetic fields such as file names or plot labels Mee OPERATION EN ee FREQUENCY MENU Frequency Span Linewidth Acquisition Time The Frequency menu is used to set the frequency span and location for the measurement Pressing the Span key selects the frequency span as the active entry field A new span may be entered from the numeric keypad or the knob may be used to adjust the span The frequency span ranges from 191 mHz to 100 kHz in factors of 2 A numerically entered span is rounded up to the next largest allowable span If the new span is incompatible with the O to 100 kHz frequency range because the start or center frequency is close to the limits of the range then the start or center frequency will be adjusted to accom
120. NDARD EVENT bit name usage STATUS BYTE 0 INP Set on input queue overflow too many commands received at once queues cleared 1 Limit Fail Set when a limit test fails 2 QRY Set on output queue overflow too many responses waiting to be transmitted queues cleared 3 Unused 4 EXE Set when a command can not execute correctly or a parameter is out of range 5 CMD Set when an illegal command is received 6 URQ Set by any key press or knob rotation 7 PON Set by power on The Standard Event status byte is defined by IEEE 488 2 1987 and is used primarily to report errors in commands received over the communications interfaces The bits in this register remain set until cleared by reading them or by the CLS command 5 29 REMOTE PROGRAMMING FFT STATUS BYTE 7 Triggered Complete New Data 0 New Data 1 Avg Complete AutoRng Change High Voltage Settle usage Set when a time record is triggered Set when a printout or plot is completed Set when new data is available for trace 0 Set when new data is available for trace 1 Set when a linear average is completed Set when auto range changes the range Set when high voltage detected at input Input range may have been switched to 34 dBV Set when settling is complete The MCS Status bits stay set until cleared by reading or by the CLS command ERROR STATUS BYTE bit Prn PIt Error Math Error RAM Error Disk
121. PUTS The input mode may be single ended A or differential A B The A and B inputs are voltage inputs with 1 15 pF input impedance Their connector shields are isolated from the chassis by 1 float or 50 1 ground Do not apply more than 50 V to either input The shields should never exceed 3V SOURCE OUTPUT The source can output either sine two tone chirp or noise waveforms The output impedance is less than 5 and is capable of driving a 50 load The output is ground referenced Mee OPERATION EN 3 3 ENN OPERATION SCREEN DISPLAY Measurement type Marker Position and data display type and trace Soft Key Definitions Pressing the value When surrounded by a number are displayed corresponding soft key will either box indicates that the knob in inverse characterson highlight a field or select an option will move the marker region the aclive trace Soft Keys 12 5 kHz Y 13 21 dbV Marker is located at the Min Max or Mean of the data within the marker region Marker Region is defined by heavy dashed lines Start center and stop frequencies of the displayed span 0 kHz 50 kHz Vertical scale Top 20 dbV 20 dB div Wndo BMH and top File z Live reference AM 2 GEV No Avg Trigger PJ Armee Live calculated Status and Window type or recalled data activity trace indicators DATA DISPLAY SINGLE and DUAL TRACE DISPLAYS Data is graphed with signal on the Y axis and There ar
122. Query the Frequency of sine tone 1 tone 2 i 0 2 to f Hz Set Query the Noise Type to white 0 or pink 1 Set Query Source Cal off 0 or on 1 noise and chirp only Do Auto Phase chirp source only description Plot the entire graph or graphs Plot the trace or traces only 5 770 FFT SPECTRUM ANALYZER PMRK PTTL s PSTL s PRSC PSET PLIM PDAT SETUP OUTP i OVRM fi KCLK i ALRM i THRS i TMIN i TSEC i DMTH 2 i DDAY i DYRS 2 i PLTM i PLTB i PLTA i PLTS i PNTR i PNGD i PNAP i PNCR i PRNT i STORE AND RECALL FILE FNAM 2 s SVTR SVTA SVST RCTR RCST MATH OPERATIONS CSEL i COPR CARG i CONS x CMRK FRONT PANEL CONTROLS STRT STCO PRSC ACTG 2 i ARNG i AUTS DATA TRANSFER SPEC g 1 BVAL g i SPEB g 2 INTERFACE RST 69 69 69 69 69 deg di 4 4 4 4 4 4 4 Plot the marker or markers only Set Query the Plot Title to string s Set Query the Plot Subtitle to string s Print the screen Same as the PRINT key Print the analyzer settings Print the Limit Table of the active graph Print the Data Table of the active graph page description 5 15 Set Query the Output Interface to RS232 0 or GPIB 1 5 15 Set Query the GPIB Overide Remote
123. R770 SP serial poll 5 35 REMOTE PROGRAMMING 800 IF SP AND 2 lt gt 2 GOTO 790 until interface is ready again command finished 810 RETURN 5 36 eee PERFORMANCE TESTS Introduction The performance tests described in this section are designed to verify with a high degree of confidence that the unit is performing within the specifications The results of each test may be recorded on the test sheet at the end of this section HARDKEYS The keypad consists of five groups of hardkeys The ENTRY keys are used to enter numeric parameters which have been highlighted by a softkey The MENU keys select a menu of softkeys Pressing a menu key will change the menu boxes which are displayed next to the softkeys Each menu groups together similar parameters and functions The CONTROL keys start and stop actual data acquisition select the marker and toggle the active trace the display These keys are not in a menu since they are used frequently and while displaying any menu The SYSTEM keys print the screen to a printer and display help messages Once again these keys can be accessed from any menu The MARKER keys determine the marker mode and perform various marker functions The marker functions can be accessed from any menu referenced braces like Hardkeys are MARKER lt Softkeys gt The SR770 has a menu driven user interface The 6 softkeys to the right of the video display have diff
124. ROPROCESSOR SYSTEM The microprocessor U101 is an 80C186 microcontroller which integrates a fast 16 bit processor counter timers interrupt controller DMA controller and I O decoding into a single component The 80C186 uses a 24 00 MHz crystal X101 as its oscilator The instruction clock cycle is 2 oscillator cycles or 12 0 MHz The data and lower 16 bits of address are multiplexed on ADO AD15 0201 0202 U203 latch the address A0 A19 at the beginning of each memory or I O cycle U204 and U205 are bidirectional data bus drivers which are active during the data read write portion of each memory I O cycle The 80C186 can address 1 Mbyte of memory and 64k of I O space The memory is mapped into 4 256kbyte blocks Each block can actually have 64k 128k or 256k of physical memory Each block has 2 sockets one for the low byte and one for the high byte of data U301 and U302 are 128kbyte EPROMS holding the program boot firmware This memory is mapped at 0000 to FFFFFH 128k U303 and U304 are 64kbyte data ROMS mapped at 80000H to 9FFFFH 128k U401 and U402 are 32kbyte CMOS static RAMs mapped at 00000H to OFFFFH 64k This memory is backed up by the battery Q401 provides power down RAM protection This memory is system memory U403 and U404 are also 32kbyte static RAMs They are mapped at 40000H to 4FFFFH 64k and are used as the display data memory Up to 16k data points may be stored in this memory Data stored
125. Rad C 806 5 00100 517 2 20 Capacitor Tantalum 35V 2096 Rad C 807 5 00100 517 2 20 Capacitor Tantalum 35V 2096 Rad C 808 5 00100 517 2 20 Capacitor Tantalum 35V 2096 Rad C 810 5 00023 529 10 Cap Monolythic Ceramic 50V 20 Z5U C 811 5 00232 520 4700 Capacitor Electrolytic 16V 20 Rad 901 5 00003 501 10 Capacitor Ceramic Disc 50V 10 SL C 902 5 00003 501 10 Capacitor Ceramic Disc 50V 10 SL C 903 5 00061 513 0010 Capacitor Mylar Poly 50V 596 Rad C 904 5 00223 513 0270 Capacitor Mylar Poly 50V 596 Rad C 905 5 00068 513 0470 Capacitor Mylar Poly 50V 596 Rad C 906 5 00061 513 0010 Capacitor Mylar Poly 50V 596 Rad C 907 5 00012 501 330P Capacitor Ceramic Disc 50V 10 SL C 908 5 00012 501 330P Capacitor Ceramic Disc 50V 10 SL C 909 5 00178 501 62 Capacitor Ceramic Disc 50V 10 SL C 910 5 00178 501 62 Capacitor Ceramic Disc 50V 10 SL 1001 5 00225 548 1U AXIAL Capacitor Ceramic 50V 80 20 Z5U AX C 1002 5 00225 548 10 AXIAL Capacitor Ceramic 50V 80 20 Z5U AX C 1003 5 00225 548 10 AXIAL Capacitor Ceramic 50V 80 20 Z5U AX C 1004 5 00225 548 10 AXIAL Capacitor Ceramic 50V 80 20 Z5U AX C 1005 5 00100 517 2 20 Capacitor Tantalum 35V 20 Rad C 1006 5 00225 548 1U AXIAL Capacitor Ceramic 50V 80 20 Z5U AX C 1007 5 00225 548 10 AXIAL Capacitor Ceramic 50V 80 20 Z5U AX C 1008 5 00225 548 1U AXIAL Capacitor Ceramic 50 80 20 250
126. TL triggers on a TTL level signal while Ext trigger has a variable threshold Source trigger works with the sine two tone and chirp sources In this mode spectra are taken with no overlap at all spans but without using the trigger circuits When each time record finishes the next one begins without delay Signals which are exactly identical in each time record will appear triggered and have a stable phase The sine and two tone sources will have stable phase if the frequencies are multiples of the linewidth The chirp source is defined in this manner Remember that the source does not turn on and off synchronously with the input time record Thus the phase of the source will be stable but arbitrary Beware that changing the span changing the source type or performing the Auto Offset calibration can all change the absolute phase of the source 4 22 en INPUT MENU Trigger Level Trigger Slope Trigger Delay This key activates the Trigger Level entry field The evel may be entered in Volts or in percent of the input range for Int trigger or percent of 5V for Ext trigger The knob only adjusts the percent value A Voltage entry outside of the limits of 100 0 to 99 22 of the applicable range will set the level to the limit The Voltage reading below the entry field displays the trigger level in Volts Note Remember that the trigger requires a minimum 100 mV pulse amplitude to successfully trigger When using the interna
127. Title The Plot menu is used to plot the screen display to an HPGL compatible plotter Use the Setup Plotter submenu to configure the plotter interface SYSTEM Plot All Plot Trace Plot Marker Subtitle Setup Plotter Abort Plot The Plot All key generates a plot of the entire graph including the scale and marker information In single trace display format only the active graph is plotted In dual trace mode both traces are plotted Each feature uses the pen assigned in the Setup Plotter submenu The marker is plotted only if it is presently displayed The Plot Trace key plots only the data trace This allows multiple data traces to be plotted on a single sheet Traces may be made in different colors by changing pen definitions or pens between plots In single trace display format only the active graph is plotted In dual trace mode both traces are plotted The Plot Marker key plots the marker if the marker is presently displayed on the screen Use the Display menu to turn the marker display on and off The marker information is plotted next to the marker This is useful when a trace has multiple peaks which need to be marked on the plot First Plot All with the marker at one location then move the marker and Plot Marker This function activates the Title entry field for alphanumeric entry The title is added to the bottom of each plot The title may be up to 40 characters long The knob scrolls the title within the entr
128. U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 100U 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1N4148 1N4148 RCA PHONO RCA PHONO HS 2128 5 DESCRIPTION Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 50V 2096 Rad Cap Monolythic Ceramic 50V 2096 Z5U Capacitor Tantalum 35V 2096 Rad Cap Monolythic Ceramic 50V 2096 Z5U Capacitor Tantalum 50V 2096 Rad Cap Monolythic Ceramic 50V 2096 Z5U Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor Ceramic 50V 80 20 Z5U AX Capacitor
129. User s Manual Model SR770 FFT Network Analyzer 5 RS Stanford Research Systems 1290 D Reamwood Avenue Sunnyvale California 94089 Phone 408 744 9040 Fax 408 744 9049 email info thinkSRS com www thinkSRS com Copyright O 1992 1993 by SRS Inc All Rights Reserved Revision 1 7 03 2006 eee TABLE OF CONTENTS GENERAL INFORMATION Entry Keys Safety and Preparation for Use iii START and PAUSE CONT Specifications V MARKER Abridged Command List1 9 viii ACTIVE TRACE AUTO RANGE GETTING STARTED AUTOSCALE Your First Measurement 1 1 SPAN UP DOWN Analyzing a Sine Wave 1 2 MARKER ENTRY Second Measurement Example 1 6 MARKER MODE Amplifier Noise Level 1 7 MARKER REF Using Triggers and the Time Record 1 10 MARKER CENTER Using the Disk Drive 1 14 MARKER MAX MIN Using Data Tables 1 20 PRINT Using Limit Tables 1 23 HELP Using Trace Math 1 27 LOCAL Using the Source 1 31 Sine 1 32 Rear Panel Two Tone 1 36 Power Entry Module Noise 1 38 IEEE 488 Connector Chirp 1 41 RS232 Connector Parallel Printer Connector Things to Watch Out For 1 46 PC Keyboard Connector ANALYZER BASICS MENUS What is an FFT Spectrum Analyzer 2 1 Frequency Menu Frequency Spans 2 2 Measure Menu The Time Record 2 3 Display Menu Measurement Basics 2 4 Marker Mode Menu Display Type 2 5 Input Menu Windowing 2 6 Scale Menu Averaging 2 7 Analyze Menu Real Time Bandwidth and Overlap 2 8 Average Menu Input Range 2 9 Source Menu The Source 2 10 System Menu Store Recall
130. V 29 25 dBV 3 544 mVrms 52 26 dBV 42 40 dBV 6 Anti Alias Filter Attenuation Input Frequency Reading Upper Limit 157 kHz lt 95 dB 7 Frequency Accuracy Input Frequency Lower Limit Reading Upper Limit 10 kHz 9 9999 kHz 10 0001 kHz 8 Phase Accuracy Frequency Trigger Slope Lower Limit Reading Upper Limit 10 kHz Rising 3 0 deg 3 0 deg Falling 177 0 deg 177 0 deg 9 Harmonic Distortion Fundamental Harmonic Frequency Reading Upper Limit 24 kHz 48 kHz 80 dB 72 kHz 80 dB 96 kHz 80 dB 6 24 ee PERFORMANCE TESTS MEN SR770 Performance Test Record 10 Noise and Spurious Signals Noise floor Start Frequency Span Reading Upper Limit 500 Hz 50 kHz 160 dBVrms VHz 50 kHz 50 kHz 160 dBVrms VHz CRT retrace frequency at approximately 15 6 kHz and retrace frequency harmonics are excepted from these limits Spurious signals Center Frequency Span Reading Upper Limit 200 Hz 390 Hz 135 dBV 500 Hz 390 Hz 140 dBV 1 kHz 1 56 kHz 140 dBV 5 kHz 1 56 kHz 140 dBV 10 kHz 1 56 kHz 140 dBV 25 kHz 1 56 kHz 140 dBV 50 kHz 1 56 kHz 140 dBV 75 kHz 1 56 kHz 140 dBV 99 kHz 1 56 kHz 140 dBV 11 Sine Source Amplitude Frequency Level Lower Limit Reading Upper Limit 1 kHz 0 dBV 0 3 dBV 0 3 dBV 1 kHz 20 dBV 20 3 dBV 19 7 dBV Amplitude Flatness Frequency Level Lower Limit Reading Upper Limit 10 kHz 0 dBV 0 3 dBV 0 3 dBV 20 kHz 0 dBV 0 3 dBV 0 3 dBV 40 kHz 0 dBV 0 3 dBV 0 3 dBV 60 kHz 0 dBV 0
131. V reference which is used to set 5V output voltages This provides very accurate digital power supply outputs 7 4 There are 2 5V supplies one to power the CPU board and disk drive 5V_P and one to power the DSP Logic Board 5 The following description refers to the 5V_P supply but describes the 5V_I and 5V and supplies as well The main pass transistor is Q5 The base of this transistor is controlled so that the emitter will provide a low impedance source of 5 VDC The current gain of Q5 remains large until the collector emitter voltage drops to about 0 4 VDC hence the low drop out voltage of the regulator The base of 5 is driven by the emitter of which is driven by the output of the op amp U3B By comparing the output of the regulator to the 5 00V reference the op amp maintains the regulator s output at 5 00 VDC The current output from the regulator is measured by the 0 1 Q resistor R10 If the current exceeds about 2 Amps then the output of U3A turns on pulling the sense input of U3B high thereby turning off the regulator s output U11 and U12 are regulators for 15 VDC U6 U7 and U18 are the 12V regulators Since these supplies do not need to be accurate output sensing is not used U9 and U10 provide 18V sources which are not referenced to the digital ground as are all of the supplies mentioned above This allows the analog inputs board to establish a ground at the signal input without digi
132. Vrms 141 09 mVrms 22 361 mVrms 3 544 mVrms a Set the AC calibrator to the amplitude in the table b Press START c Record the marker Y reading 4 This completes the amplitude accuracy and frequency response test Enter the results of this test in the test record at the end of this section 6 12 eee PERFORMANCE TESTS 6 Anti alias Filter Attenuation This test measures the attenuation of the anti alias filter This tests how well the analyzer rejects frequencies outside the 100 kHz frequency range Setup We will use the frequency synthesizer to provide the signal Connect the output of the frequency synthesizer to the A input of the analyzer Be sure to use the appropriate terminations where required Procedure 1 PRESET Turn the analyzer off wait a few seconds then back on with the key pressed 2 Setthe frequency synthesizer to a frequency of 99 kHz and an amplitude of 446 mVrms 3 Press the keys in the following sequence FREQ Span 1 5 kHz Center Freq gt 9 9 kHz INPUT Input Range 2 lt 9 gt AUTO SCALE MARKER MAX MIN 4 Adjust the synthesizer amplitude so that the marker Y value reads 4 0 dB 0 2 dB 5 Press AVERAGE Number of Averages 2 0 Enter lt Averaging gt Select On MARKER REF 6 Set the synthesizer frequency to 157 kHz 7 Press START 8 Record the marker Y reading 9 This completes the anti alias filter atte
133. ached to the rear panel parallel printer port The printer type needs to be configured before using the PLIM command The PDAT command will print the data table for the active trace to a printer attached to the rear panel parallel printer port The printer type needs to be configured before using the PDAT command 5 17 REMOTE PROGRAMMING SETUP COMMANDS OUTP i OVRM 2 i KCLK 2 i ALRM 2 i THRS 2 i TMIN 2 i TSEC 7 i DMTH 7 i DDAY 7 i DYRS 7 i PLTM 7 i PLTB 2 i PLTA 7 i PLTS 2 i PNTR 2 i PNGD 7 i The OUTP command sets the output interface to RS232 i 0 or GPIB i 1 The OUTP i command should be sent before any query commands to direct the responses to the interface in use The OVRM command sets or queries the GPIB Overide Remote Yes No condition The parameter i selects No i 0 or Yes 0 1 The KCLK command sets or queries the key click On i21 or Off i20 state The ALRM command sets or queries the alarm On i 1 or Off 150 state The THRS command sets or queries the hours setting of the clock The value of i is in the range 0 O i 023 The TMIN command sets or queries the minutes setting of the clock The value of i is in the range 0 159 The TSEC command sets or queries the seconds setting of the clock The value of i is in the range 0 O 159 The DMTH command sets or queries the m
134. adjust the marker When the disk catalog is displayed the marker highlights a file Use the knob to choose the file TEST1 to recall Or use the File Name key to enter the file name This recalls the settings from the file TEST1 The analyzer settings are changed to those stored in TEST1 The span and input coupling should be the same as those in effect when you created the file Note that the STOP Invld indicator is flashing at the bottom of the screen This means that the display data does not match the analyzer settings or the graph parameters Remember we just recalled the settings which paused the data acquisition before changing the settings Pressing START will start data acqusition with the new settings ENN GETTING STARTED M USING DATA TABLES A data table reports the Y values for user listed X axis values For example the entries could be a set of harmonic frequencies which need to measured The data table is a convenient way to measure the data values at various points without moving the marker around and manually recording the answers To generate a printed report of the measurement the data table may be printed using the Plot menu Each trace has its own data table though only the table associated with the active trace is on and displayed at any time Data tables are saved along with the trace data when data is saved to disk Data tables are not stored in non volatile memory and are not retained when
135. aging Type either RMS Vector or Peak Hold RMS Averaging This averages the magnitude of the spectra in an RMS fashion The displayed data is the square root of the weighted mean of the sum of the magnitudes squared FFT times its complex conjugate The weighting is either linear or exponential RMS averaging reduces fluctuations in the data but does not reduce the actual noise floor With a sufficient number of averages a very good approximation of the actual random noise floor can be displayed Note Since the RMS averaging is done on magnitudes only displaying the real or imaginary part or phase of an RMS average has no meaning The RMS average has no complex information If the real or imaginary part or phase is being displayed the display will not update when RMS averaging is on Vector Averaging Vector averaging averages the complex spectrum This can reduce the noise floor for random signals since they are not phase coherent from time record to time record Vector averaging requires a trigger The input signal must be both periodic and phase synchronous with the trigger Otherwise the real and imaginary parts of the signal will not add in phase and instead will cancel randomly With vector averaging the real and imaginary parts as well as phase displays are correctly averaged and displayed This is because the complex information is preserved Peak Hold Peak Hold is not really averaging rather the new spectral magn
136. ains the signal components whose period is longer than the time record not only dc So our final displayed spectrum contains 400 frequency bins The first covers 0 250 Hz the second 250 500 Hz and the 400th covers 99 75 100 0 kHz Spans less than 100 kHz So the length of the time record determines the frequency span and resolution of our spectrum What happens if we make the time record 8 ms or twice as long Well we ought to get 2048 time points sampling at 256 kHz yielding a spectrum from dc to 100 kHz with 125 Hz resolution containing 800 points But the SR770 places some limitations on this One is memory If we keep increasing the time record then we would need to store more and more points Another limitation is processing time The time it takes to calculate an FFT with more points increases more than linearly The net result is that the SR770 always takes 1024 point FFT s to yield 400 point spectra Here s how it s done The analyzer digitally filters the incoming data samples at 256 kHz to limit the bandwidth This is similar to the anti aliasing filter at the input except the digital filter s cutoff frequency can be changed In the case of the 8 ms record the filter reduces the bandwidth to 64 kHz with a filter cutoff of 50 kHz the filter rolls off between 50 and 64 kHz Remember that Nyquist only requires samples at twice the frequency of the highest signal frequency Thus the digital filter only has to output
137. al SYSTEM Output To RS 232 Baud Rate RS 232 Word Length RS 232 Parity GPIB Address Override Remote Key Click Alarms Plot Mode Plotter Baud Rate Plotter GPIB Address Plot Speed Trace Pen Grid Pen Alpha Pen Marker Pen Printer Type STORE RECALL File Name Linear None Off 2 RMS Linear 0 0 max for span Off 1 00 kHz 1000 mV 1 00 kHz 500 mV 9 00 kHz 500 mV White 1000 mV 1000 mV On Chirp and Noise only GPIB 9600 8 bits None 10 No On On RS 232 9600 ENN DEFAULT SETTINGS STATUS ENABLE REGISTERS Cleared en DEFAULT SETTINGS 4 87 De REMOTE PROGRAMMING INTRODUCTION The SR770 FFT Spectrum Analyzer may be remotely programmed via either the RS232 or GPIB IEEE 488 interfaces Any computer supporting one of these interfaces may be used to program the SR770 Both interfaces are receiving at all times however the SR770 will send responses only to the interface specified in the System Setup menu Output To RS232 GPIB function Use the OUTP command at the beginning of every program to direct the responses to the correct interface All front panel features except power may be controlled COMMUNICATING WITH GPIB The SR770 supports the IEEE 488 1 1978 interface standard It also supports the required common commands of the IEEE 488 2 1987 standard Before attempting to communicate with the SR770 over the GPIB interface the SR770 s device a
138. al to the internal 30 MHz clock Flip Flop U305 latches the trigger signal and stays high until cleared Flip Flops U306A and 03068 synchronize the trigger signal to the A D sampling clock and DSP serial port TIMING SIGNAL GENERATOR The timing signal generator provides all timing signals for the A D Converter Trigger Circuitry and DSP processor serial ports U608 is a PAL which implements a 118 state 7 bit counter U609 is also a PAL and implements a 118 state state machine and generates all the timing signals needed on the DSP Logic Board U610 is a high speed latch used 7 6 to latch the state of the timing generator when a trigger signal is detected INTERFACE TO CPU BOARD The I O interface provides the communication pathway between the DSP Logic Board and the main CPU Board U601 and U602 are buffers for the address and data bus connections Both buffer chips are enabled only when the CPU Board is writing to the DSP Logic Board This helps isolate the activity on the CPU Board from affecting circuitry on the DSP Logic Board U603 and U604 are simple D type latches used to hold configuration data for the DSP Logic Board U605 is the main decoder PAL and generates all of the chip selects and strobes needed by the DSP Logic Board SOURCE GENERATOR The source generator has its own digital signal processor an ADSP 2105 The ADSP 2105 has its own ROM and RAM and runs on its own Commands are passed to it via the 8 bit DA
139. are automatically named SCRNXXXX PCX PCX files can be imported directly into many paint and draw programs on a PC This allows SR770 screens to be easily incorporated into documents on a PC Press the PRINT key to print the screen on the printer or to a file Settings Limits and Data Tables may NOT be saved as a file 4 69 SYSTEM MENU Return This key returns to the System menu Setup Screen The Setup Screen submenu is used to adjust the position of the display on the Move Right Move Left Move Up screen The display area may be moved left right up and down SYSTEM SETUP Screen Move Down Return The screen position is stored in non volatile memory and is retained when the power is turned off To restore the screen to the default position power the unit on with the lt backspace key pressed Move Right This function moves the display to the right on the screen Move Left This function moves the display to the left on the screen Move Up This function moves the display up on the screen Move Down This function moves the display down on the screen Return The Return key will return to the main Setup menu 4 70 en SYSTEM MENU EN 4 71 SYSTEM MENU Test Hardware Keypad Test 9 Keyboard Test Knob Test Disk Drive Test More More 9 Return Keypad Test Keyboard Test Knob Test Disk Drive Te
140. arize the user with the disk drive We will use the SR770 Source to provide a test signal so that there is some data to save and recall Specifically you will save and recall a data file and a settings file eee GETTING STARTED EN STORING AND RECALLING DATA 1 Turn the analyzer on while holding down the lt backspace key Wait until the power on tests are completed 2 Connect the SR770 Source output to the A input Press SOURCE Press lt Sine gt 3 Press AUTO RANGE 4 Press SPAN DOWN until the span is 6 25 kHz 5 Press AUTO SCALE 6 Press PAUSE CONT 7 Put a blank double sided high density DS HD 3 5 disk into the drive 8 Press STORE RECALL Press Disk Utilities Press Format Disk 9 Press Return Press Save Data When the power is turned on with the backspace key depressed the analyzer returns to its default settings See the Default Settings list in the Menu section for a complete listing of the settings Display the Source menu Turn on the Sine output Leave the sine frequency and level at the default settings 1 kHz and 1 Vpk Let the analyzer automatically set its input range Set the span to display the 1 kHz signal Set the graph scaling to display the entire range of the data Stop data acquisition The graph on the screen is the one we want to save You can actually save graphs while the analyzer is running Use a blank if disk if possible
141. arker reading should be in dBV DHz This is the output noise amplitude at the marker frequency normalized to a 1 Hz bandwidth To generalize to other bandwidths multiply by the square root of the bandwidth This approximation only holds if the noise is Gaussian in nature eee GETTING STARTED EN Press MEAS Press Units Menu Press Volts RMS 8 Disconnect the source output from the amplifier Leave the amplifier input terminated with 50 Ohms 1 9 Display the Measure menu Choose the Units menu Select Volts RMS as the display units The marker now reads in Volts RMS 2 This is a typical way of specifying amplifier input noise levels Now we are measuring the amplifier s output noise with a shorted input If you take the noise measurement and divide by the amplifier gain then you will have the amplifier s input noise at the frequency of the marker reading An FFT is a convenient tool for measuring amplifier noise spectra since the noise at many frequencies can be determined in a single measurement ENN GETTING STARTED M USING TRIGGERS AND THE TIME RECORD This sample measurement is designed to acquaint the user with the triggering capabilities of the SR770 Network Analyzer Do not be concerned that your measurement does not exactly agree with this exercise The focus of this measurement exercise is to learn how to use the instrument There are two types of front panel keys which will be referenced
142. ata at any address may be read or written This allows drawing to take place as fast as possible Commands and data are sent from the 80C186 to the HD63484 using a DMA channel This allows the HD63484 to process commands without having to wait for the 80C186 to send them DISK CONTROLLER U907 is a DP8473 disk controller which integrates all of the functions of the PC interface into a single IC All motor controls read and write signals and data are all controlled by the DP8473 A DMA channel is used to send and receive data from the controller in order to satisfy the disk drive timing GPIB INTERFACE The GPIB IEEE 488 interface is provided by 0902 a TMS9914A controller 0903 and 0904 buffer data I O to the GPIB connector U902 is programmed to provide an interrupt to the processor whenever there is bus activity addressed to the unit RS232 INTERFACE The SCN2641 UART U905 provides all of the UART functions as well as baud rate generation Standard baud rates up to 19 2k can be generated from the 3 6864 MHz clock U906 buffers the outgoing data and control signals Incoming signals are received by U705A and U705B If the host computer asserts DTR RS232 data output from the unit will cease The RS232 port is a DCE and may be connected to a PC using a standard serial cable not a null modem cable EXPANSION CONNECTOR All control of the data acquisition hardware is through the signals on the 30 pin expansion connec
143. ata streams sent one representing real data and the other representing imaginary data U105 stores an output flag so that the second DSP can distinguish real data points from imaginary data points U106 is a PAL which provides some decoding logic for I O strobes and interrupt lines also performs some computations in hardware for the first DSP The second DSP processor U201 is responsible for FFT computations trigger computations averaging algorithms output display processing Data from the first DSP is received by the second DSP via its serial receive port and stored in a buffer FFT s are performed on the data in the buffer once the buffer is filled with a sufficient number of points After the FFT is computed phase corrections are made using information from the trigger circuitry if trigger is enabled The FFT is then averaged with previous FFT spectra if averaging is enabled Lastly the spectra is prepared for display on the CRT screen Depending upon the user s request scaling log or sqrt functions need to be performed on the FFT spectra TRIGGER The Trigger function of the SR770 allows the user to control when the instrument will start taking data for the FFT computation For example a user wishes to examine the spectrum of a transient induced by a hammer blow to mechanical structure A transducer connected to the hammer provides a pulse upon impact of the hammer That pulse can be used to trigger
144. ate termination Procedure PRESET Turn the analyzer off wait a few seconds then back on with the key pressed Set the low distortion oscillator to a frequency of 24 kHz and an amplitude of 70 mVrms Press the keys in the following sequence INPUT Input Range 1 6 lt dBV gt AUTO SCALE MARKER MAX MIN Adjust the oscillator frequency to 24 0 kHz Adjust the oscillator amplitude until the marker Y reading is 20 0 dBV 0 2 dBV Press AVERAGE lt Number of Averages gt 2 0 lt Enter gt lt Averaging gt Select On MARKER REF ANALYZE lt Harmonic gt Repeat steps 6a through 6 three times to measure the harmonics in the table below Fundamental Harmonic Harmonic Frequency 24 0 kHz 2 48 kHz 3 72 kHz 4 96 kHz a Press lt Harmonics gt 2 lt Enter gt b Press lt Next Harmonic gt gt to move the marker to the next harmonic to the right c Record the marker Y reading 6 17 PERFORMANCE TESTS 7 Press MARKER Use the knob to move the marker to a region between the 2nd and 3rd harmonics Make sure that the marker is reading a point representative of the noise floor Note the marker Y value If the noise floor is above 93 dB then the harmonic distortion measurements are invalid A generator with a lower noise floor is required This completes the harmonic distortion test Enter the results of this test in the test record at the end of this sectio
145. ay be programmed Measurement Possible Displays Spectrum All PSD Log Mag Lin Mag Time Record All Octave Log Mag The UNIT command sets or queries the display units for trace g The parameter i selects Volts Pk i 0 Volts RMS i21 2 or dBVrms i 3 If Engineering Units are being used then EU Pk EU RMS dBEU and dBEUrms are selected If Phase is being displayed then i selects Degrees i 0 or Radians i 1 VOEU command sets or queries the unit type for trace g i 0 selects Volts and i 1 selects EU s The EULB command sets or queries the EU label for trace g The string s is a string of up to 6 characters The EUVT command sets or queries the EU scaling for trace g The EUVT x command sets the scaling to x EU s per Volt The WNDO command sets or queries the windowing function The parameter i selects Uniform i20 Flattop i21 Hanning 152 or Blackman Harris i73 When querying the window the WNDO g command queries the window of the trace g This may differ from the live window because the trace may be a recalled file with its own window When setting the window the WNDO g i command sets the live window for both traces The parameter g is required but both live trace windows are affected 5 6 ee REMOTE PROGRAMMING DISPLAY and MARKER COMMANDS ACTG i FMTS 2 i GRID 2 i FILS g 0 MRKR 2 1 2 MRKM 2 g Lii MRLK
146. bbon Switch Panel Mount Power Rocker SOFTPOT Thermostat Varistor Zinc Oxide Nonlinear Resistor Trim Pot Cond Plastic PC Mount Thermistor ICL Inrush Current Limiter Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Fuse Misc Components Transformer Fabricated Part Machined Part Injection Molded Plastic Fabricated Part Fabricated Part Fabricated Part Machined Part Fabricated Part Fabricated Part Fabricated Part Fabricated Part 7 29 EN PARTS LST REF 20 20 20 20 20 SRS PART 7 00393 720 7 00396 701 7 00403 720 7 00404 720 7 00406 720 7 00407 720 7 00409 720 7 00414 720 7 00421 735 7 00431 720 7 00432 720 7 00433 720 7 00434 721 7 00435 720 7 00436 701 7 00437 701 7 00458 720 7 00459 720 7 0047 1 720 7 00473 720 7 00495 740 7 00519 709 7 007 18 720 8 00034 850 8 00040 840 9 00267 917 VALUE SR770 5 PLTFM FP SR770 9 SR770 10 SR770 12 SR770 13 SR770 15 amp 16 SR770 17 PLTFM 9 THRU 13 SR770 21 22 SR770 23 SR770 24 SR770 25 SR770 26 FFT DSP LI FFT DSP LI SR850 6 58850 7 SCREEN SR770 27 28 29 SR770S 1 FFT SR770 33 FLOPPY 7 Z AXIS GENERIC Miscellaneous Parts List REF U 301 U 302 U 303 U 304 U 504 Z0 SRS PART 3 00450 342 3 00450 342 3 00345 342 3 00345 342 3 00345 342 0 00089 033 0 00159 000 0 00179 000 0 00180 000 0 00185 021 0 00187 021 0 00204 000 0 00223 029 0 00248 026 0 00259 021 0 00315 021
147. ce key depressed the analyzer returns to its default settings See the Default Settings list in the Menu section for a complete listing of the settings Display the Source menu Turn on the Chirp output Let the analyzer select the input range The Chirp source provides an equal amplitude sine wave at each bin of the displayed spectrum The phases of each sine wave are arranged so that they do not add in phase and the resulting output does not peak Because of cancellation not all sine waves are present during all portions of the time record Since the input time record is windowed some portions of the time record are attenuated This results in certain frequency ranges in the spectra being attenuated Hence the spectrum has peaks and valleys and is generally not useful when windowed Display the Measure menu Show the Window menu Select a Uniform window no windowing The spectrum becomes an almost flat line Since the chirp waveform consists of the 400 displayed bin frequencies it is EXACTLY periodic over a time record Every time record is the same except for noise An exactly periodic waveform requires no window In this case the window actually removes spectral information which we need Display the Input menu Go to the Trigger menu Select Source Trigger This is a special trigger 1 42 eee GETTING STARTED EN Press Return Press Auto Offset to select Off 5 Press SCALE Press lt Y Div gt
148. ce capable of providing a variety of test signals SINE A low distortion sine wave for general purpose gain distortion and signal noise measurements The sine source is synchronous with the FFT i e sine waves can be generated at exact bin frequencies of the FFT This can eliminate windowing effects in the measured amplitude and phase TWO TONE Two low distortion sine waves can be generated simultaneously for intermodulation distortion tests IMD Each tone has independent frequency and amplitude settings NOISE Broadband noise is useful for characterizing circuits mechanical systems or even the audio response of an entire room White noise provides equal amplitude per root Hz from 0 to 100 kHz White noise is useful in electronic applications Pink noise rolls off at 3 dB oct providing equal amplitude per octave Pink noise is preferred in audio applications CHIRP The Chirp source provides an equal amplitude sine wave at each bin of the displayed spectrum Since there are 400 bins in a spectrum the chirp is the sum of 400 discrete sine waves The phases of each sine wave are arranged so that they do not add in phase and the resulting output does not peak This source is useful for measuring transfer functions quickly without having to make many discrete measurements using a single sine wave There are two types of front panel keys which will be referenced in this section Hardkeys are those keys with labels printed on th
149. command queries the entries for line i only The data is returned in the form j f1 f2 Y 1 Y2 If The LTBL ij f1 f2 y1 y2 command sets the entries of line i to O upper 1 lower f1 Xbegin f2 Xend y1 Y1 and y2 Y2 If i is greater than the last line number in the table the new line will be added to the end of the table The LINX command sets or queries the table index highlighted line number The parameter i ranges from 0 to 99 If i is greater than the last index in the table then a new line is added to the end of the table The LINS command inserts a new line before the table index highlighted line The new line becomes highlighted The LIDT command deletes the table index highlighted line The LLTB command deletes the entire table The LARM command sets or queries the audio limit fail alarm on off condition The parameter i selects alarm Off i20 or Enabled i21 5 14 ee REMOTE PROGRAMMING AVERAGING COMMANDS AVGO i NAVG i AVGT i 2 i OVLP x The AVGO command sets or queries the averaging on off condition The parameter i selects averaging Off i20 or On i71 The NAVG command sets or queries the number of averages The parameter i ranges from 2 to 32767 The AVGT command sets or queries the average type The parameter i selects RMS 0 0 Vector i21 or Peak Hold 122 The AVGM command sets or queries the averaging mode The parameter i selects
150. cord the marker Y reading for the 60 dB range 6 5 PERFORMANCE TESTS 4 This completes the DC measurement test Enter the results of this test in the test record at the end of this section 6 6 eee PERFORMANCE TESTS 3 Common Mode Rejection This test measures the common mode rejection of the analyzer Setup We will use the frequency synthesizer to provide the signal Connect the output of the frequency synthesizer to both the A and B inputs of the analyzer Use equal length cables from A and B to a BNC TEE Connect the cable from the synthesizer output to the TEE using the appropriate feedthrough termination Procedure 1 PRESET Turn the analyzer off wait a few seconds then back on with the key pressed 2 Setthe frequency synthesizer to a frequency of 1 kHz and an amplitude of 446 mVrms 3 Press the keys in the following sequence FREQ Span 1 5 kHz Center Freq gt 1 kHz INPUT Input Range 2 lt 9 gt AUTO SCALE MARKER MAX MIN AVERAGE Number of Averages 2 0 Enter lt Averaging gt Select On MARKER REF INPUT lt Input Source gt Select A B START 4 Record the marker Y reading This is the CMRR in dB at 1 kHz 5 This completes the CMRR measurement test Enter the results of this test in the test record at the end of this section 6 7 PERFORMANCE TESTS 4 Amplitude Accuracy and Flatness This test measures th
151. ction of each DSP Each DSP contains two external busses a memory bus and a host processor bus The memory bus is connected to 32K of 24 bit Static RAM SRAM as well as some decoding logic for access to I O devices The Host processor bus is connected to the main CPU Board via the I O Interface on the DSP Logic Board The CPU Board acts as the host processor to the DSP s and controls all of their functions DSP firmware and commands are downloaded from the CPU Board to invoke different operating modes Each DSP also has two dedicated serial ports one for receiving and one for transmitting These ports are used for transferring partially processed data The first DSP processor U101 is responsible for frequency shifting the input signal from the A D converter filtering and downsampling In short the first DSP Processor extracts a select portion of the frequency spectrum from the digitized input signal for example the spectrum from 99 7 kHz to 7 5 99 8 kHz and reduces the sampling rate of the resulting data stream to reflect the bandwidth of the selected frequency span Recall that the sampling rate must be at least twice that of the frequency span Data is received from the A D Converter via its dedicated serial receive port The results of the heterodyning filtering downsampling are passed on to the second DSP via the serial transmit port Because data sent to the second DSP is in complex form there are actually two d
152. cuit Integrated Circuit Integrated Circuit Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Thru hole Pkg Integrated Circuit Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg nn nT Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Transistor TO 92 Package Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Voltage Reg TO 220 TAB Package Voltage Reg TO 220 TAB Package Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Transistor TO 92 Package Transistor TO 92 Package Transistor TO 92 Package Transistor TO 92 Package Transistor TO 92 Package Voltage Reg TO 220 TAB
153. d The ALT key allows letters to be entered DOS file name conventions must be followed i e file names are 8 characters or less with an extension of up to characters ABCDEFGH XYZ is a valid file name DOS sub directories are not supported All files are saved to the root directory This key toggles the file catalog display screen on and off The use of this key is identical to the Catalog On Off function in the Save Data submenu describe previously The Return key will return to the main Store Recall menu Return also removes the catalog display screen and restores the graph 4 80 en STORE RECALL MENU Recall Data Recall Data I File Name TEST DAT Catalog On The Recall Data submenu is used to read data from a disk file onto the active trace graph Note that the graph parameters measurement display units and window are all recalled with the data and appear in the menus for the active trace The graph will be labelled with the recalled frequency span but the Frequency menu will still display the live settings The file name appears below the graph The Limit and Data tables are also recalled with the data Recall Data File Name Catalog On Off the graph Return Pressing this key will recall data and limit and data tables from the file specified in the File Name field If the file specified is not on the disk or is not a data file then an error message will appear This
154. d off If the memory check passes then the instrument returns to the settings in effect when the power was last turned off If there is a memory error then the stored settings are lost and the default settings are used ROM This test checks the processor ROM CLR This test indicates whether the unit is being reset To reset the unit hold down the 3 1 Front Panel BNC Connectors backspace lt key while the power is turned on The unit will use the default settings The default setup is listed in a later chapter CLK This test checks the CMOS clock and calendar for a valid date and time If the there is an error the time will be reset to a default time Change the clock settings using the SYSTEM SETUP menu DSP This test checks the digital processors and fast memory signal AID This test checks the analog to digital converter board RESET Holding down the backspace lt key while the power is turned on resets the unit The unit will use the default settings as listed at the end of the Menus section of the manual VIDEO DISPLAY The monochrome video display is the user interface for data display and front panel programming operations The resolution of the display is 640H by OPERATION 480V The brightness is adjusted using the brightness control knob located at the upper left corner As with most video displays do not set the brightness higher than necessary The display may be adjusted left
155. d 2 gt Rotate the knob to verify rotation and direction lt Return gt lt More gt lt Memory Test gt lt Main Mem gt lt Begin Test gt All of the main memory chips should Pass lt Return gt lt Video Mem gt lt Begin Test gt All of the video memory chips should Pass lt Return gt lt Return gt lt DSP Test gt Both DSP chips should report 0 errors Press any key to exit this test 3 This completes the functional hardware tests Enter the results of this test in the test record at the end of this section 6 4 ee PERFORMANCE TESTS 2 DC Offset This test measures the DC offset of the input Setup Connect a 500 feedthrough termination to the A input This shorts the input so the analyzer s own DC offset will be measured Procedure 1 PRESET Turn the analyzer off wait a few seconds then back on with the key pressed 2 Press the keys in the following sequence FREQ Span 1 lt kHz gt DISPLAY Marker Width Select Spot Marker MARKER Rotate the knob so that the marker is at DC The marker readout above the graph should read 0 0 kHz AVERAGE Number of Averages 2 0 Enter lt Averaging gt Select On INPUT lt Coupling gt Select DC 3 Press lt Input Range gt 3 0 lt gt START AUTO SCALE b Record the marker Y reading for the 30 dB range c Press lt Input Range gt 6 0 START AUTO SCALE d Re
156. dbs 400 double array of dB data void main void int i eos char serPol char tstr 30 double full_scale if sr770 ibfind fft770 lt O printf nCannot Find FFFT Device n a exit 1 txsr770 RST return sr770 to default state txsr770 STOP stop data acquisition txsr770 NAVG1000 set 1000 averages txsr770 AVGO1 turn averaging on txsr770 STRT start the average do ibrsp sr770 amp serPol f wait for the average to complete while serPol amp 1 0 by polling for no scans in progress printf nScan Finished Acquiring Spectrum n now we turn off the terminate read on eos to enable us to use ibrd with the binary dump command Note also that we cannot use txsr770 with the SPEB command because IFC RDY will not be set until gt after lt the spectrum has been read ibeos sr770 0 n turn off terminate on EOS since binary data will be coming back and a 10H may be one of the values ibwrt sr770 SPEB 0 6 binary dump graph 0 ibrd sr770 char rxBuff 800 read 800 bytes of spectrum ibeos sr770 REOS n restore terminate on EOS for future commands printf n d Bytes Read Calculating Y Values n ibcnt getch f wait for keypress To calculate db values from the binay data we use the following formula dbFullScale 114 3914 n 3 0103 152 for i 0 i lt 400 i dbs i 114 3914
157. ddress must be set The address is set in the Setup GPIB menu and may be set between 0 and 30 COMMUNICATING WITH RS232 The SR770 is configured as a DCE transmit on pin 3 receive on pin 2 device and supports CTS DTR hardware handshaking The CTS signal pin 5 is an output indicating that the SR770 is ready while the DTR signal pin 20 is an input that is used to control the SR770 s data transmission If desired the handshake pins may be ignored and a simple 3 wire interface pins 2 3 and 7 may be used The RS232 interface baud rate number of data bits and parity must be set These are set in the Setup RS232 menu STATUS INDICATORS AND QUEUES To assist in programming the SR770 has 4 interface status indicators which are displayed at the bottom of the screen The RS232 GPIB Activity indicator flashes whenever a character is received or transmitted over either interface The ERR indicator flashes when an error such as an illegal command or parameter out of range has been detected The REM indicator is on whenever the SR770 is in a remote state front panel locked out The SRQ indicator is on when the SR770 generates a service request SRQ stays on until a serial poll is completed 5 1 To help find program errors the SR770 can display the interface buffers on the screen This screen is activated by the View Queue function in the Setup Communications menu The last 256 characters received and transmitted by the SR770 ar
158. de values are stored in the original complex form If the real or imaginary part or phase is being displayed for spectrum measurements the display shows the real or imaginary part or phase of the complex peak value Linear Averaging Linear averaging combines N number of averages spectra with equal weighting in either RMS Vector or Peak Hold fashion When the number of averages has been completed the analyzer stops and a beep is sounded When linear averaging is in progress the number of averages completed is continuously displayed below the Averaging indicator at the bottom of the screen Auto ranging is temporarily disabled when a linear average is in progress Be sure that you don t change the input range manually either Changing the range during a linear average invalidates the results Exponential Averaging Exponential averaging weights new data more than old data Averaging takes place according to the formula New Spectrum 1 N AverageN 4 N 1 N where N is the number of averages Exponential averages grow for approximately the first 5N spectra until the steady state values are reached Once in steady state further changes in the spectra are detected only if they last sufficiently long Make sure that the number of averages is not so large as to eliminate the changes in the data that might be important ANALYZER BASICS REAL TIME BANDWIDTH AND OVERLAP PROCESSING What
159. diately sets the Span to 100 kHz Linewidth to 250 Hz Acquisition Time to 4 00 ms Start Frequency to 0 0 Hz and Center Frequency to 50 0 kHz The Start Frequency key selects the start frequency of the span as the active entry field The knob adjusts the start frequency in steps equal to the linewidth A numerically entered frequency is rounded to the nearest frequency bin exact multiple of the linewidth If the new start frequency is incompatible with the span because of the 0 to 100 kHz range limits then the start frequency will be set to the closest allowable value The Center Frequency key selects the center frequency of the span as the active entry field The knob adjusts the center frequency in steps equal to the linewidth A numerically entered frequency is rounded to the nearest frequency bin exact multiple of the linewidth If the new center frequency is incompatible with the span because of the O to 100 kHz range limits then the center frequency will be set to the closest allowable value Note Activating the Start or Center Frequency fields fixes the start or center frequency for subsequent adjustments to the frequency span Further adjustments to the span leave the span start or center untouched even when the start or center frequency becomes de activated as a menu choice The most recently activated of the Start or Center Frequency fields sets the span adjustment mode Enlarging the frequency span may change the start and c
160. does not affect the display scaling whether linear or logarithmic The Marker and data readouts reflect the choice of units but the graph remains unchanged 4 10 en MEASURE MENU EN Window Uniform FN Q Flattop o SZ Return Uniform Flattop Hanning BMH The Window submenu allows the user to choose the window function Both traces use the same window function A trace may be recalled from disk with a window different than the live window This is the only case where the window on the graph is other than the live window shown in this menu This key selects no windowing uniform or rectangular window function of the time record This window provides high amplitude accuracy only for frequencies exactly on a bin and poor frequency selectivity making it a poor choice for continuous signals It is primarily useful for analyzing impulses and transients which are shorter than a time record This key selects the Flattop window This window has the least ripple and thus the smallest amplitude errors for frequencies not exactly on a bin It is most useful for precise amplitude measurements This key selects the Hanning window The Hanning window has a relatively narrow mainlobe and low sidelobes providing low leakage spectral broadening and good selectivity This key selects the Blackman Harris window This window has the narrowest mainlobe and the fastest roll off for the best selectivity T
161. e 0 or A weighting 1 page description 5 5 Set Query the Measurement Type to Spectrum 0 PSD 1 Time 2 or Octave 3 5 5 Set Query the Display to LogMag 0 LinMag 1 Real 2 Imag 3 or Phase 4 5 5 Set Query the Units to Vpk or deg 0 Vrms rads 1 dBV 2 or dBVrms 3 5 5 Set Query the Units to Volts 0 or EU 1 5 5 Set Query the EU Label to string s 5 5 Set Query the EU Value to x EU Volt 5 5 Set Query the Window to Uniform 0 Flattop 1 Hanning 2 or BMH 3 page description 5 6 Set Query the Active Trace to traceO 0 or trace1 1 5 6 Set Query the Display Format to Single 0 or Dual 1 trace 5 6 Set Query the Grid mode to Off 0 8 1 or 10 2 divisions 5 6 Set Query the Graph Style to Line 0 or Filled 1 5 6 Set Query the Marker to Off 0 On 1 or Track 2 5 6 Set Query the Marker Width to Norm 0 Wide 1 or Spot 2 5 6 Set Query the Marker Seeks mode to Max 0 Min 1 or Mean 2 5 6 Set Query the Linked Markers to Off 0 or On 1 5 6 Move the marker region to bin i 5 6 Query the Marker X position 5 6 Query the Marker Y position 5 6 Move the Marker to the on screen max or min Same as MARKER MAX MIN key 5 6 Make the Marker X position the center of the span Same as MARKER qA Co ag
162. e If the knob is turned while making a numeric entry but before a units key has been pressed the knob will adjust the marker position instead Some entry fields allow only knob adjustment or only numeric entry START and PAUSE CONT The START and PAUSE CONT keys are used to start pause and continue data acquisition If the unit is in the RUN mode acquiring and displaying data as indicated by the RUN indicator then the PAUSE CONT key will halt data acquisition The RUN indicator switches to STOP and no new spectra will be taken and the display will not be updated If averaging is off then either the START key or the PAUSE CONT key will resume acquisition If averaging is on the START key will reset the average and restart acquisition PAUSE CONT on the other hand will continue the average where it was paused In the case of linear averaging when the average is already completed the PAUSE CONT does nothing since there is no average to continue MARKER Pressing the MARKER key highlights the marker information field by drawing a box around it The knob will now scroll the marker region The highlighted marker field appears below 12 5 kHz Y 13 21 dbV LogMag Sp OPERATION ee Any previously highlighted parameter field will become non highlighted Pressing a soft key to highlight a new parameter field will let the knob adjust the new parameter while the marker becomes unselected ACTIVE TRACE
163. e displayed COMMAND SYNTAX Communications with the SR770 uses ASCII characters Commands may be in either UPPER or lower case and may contain any number of embedded space characters A command to the SR770 consists of a four character command mnemonic arguments if necessary and a command terminator The terminator must be a linefeed If2 or carriage return cr on RS232 or a linefeed If or on GPIB No command processing occurs until a command terminator is received Commands function identically on GPIB and RS232 whenever possible Command mnemonics beginning with an asterisk are IEEE 488 2 1987 defined common commands These commands also function identically on RS232 Commands may require one or more parameters Multiple parameters are separated by commas Multiple commands may be sent on one command line by separating them with semicolons The difference between sending several commands on the same line and sending several independent commands is that when a command line is parsed and executed the entire line is executed before any other device action proceeds There is no need to wait between commands The SR770 has a 256 character input buffer and processes commands in the order received If the buffer fills up the SR770 will hold off handshaking on the GPIB and attempt to hold off handshaking on RS232 Similarly the SR770 has a 256 character output buffer to store output until the host computer
164. e Error Status Byte when finished The Disk Error bit may be checked to make sure that the Save Trace SVTR command terminated without error Since the Save Trace command may take a long time to execute it is important that the host computer interface does not time out while waiting for the response to the ERRS query In the case where the host interface times out before the ERRS response the host program must wait before sending the ERRS query GET GROUP EXECUTE TRIGGER The GPIB bus command GET will have the same effect as a trigger If the analyzer is in a triggered mode and awaiting a trigger and the trigger is armed then the GET bus command will trigger a time record If the trigger mode is continuous or the trigger is not armed then the GET command does nothing To setup the analyzer in an awaiting trigger simply choose external TTL trigger and leave the trigger unconnected ee REMOTE PROGRAMMING DETAILED COMMAND LIST The four letter mnemonic in each command sequence specifies the command The rest of the sequence consists of parameters Multiple parameters are separated by commas Parameters shown in are optional or may be queried while those not in are required Commands that may be queried have a question mark parentheses after the mnemonic Commands that may ONLY be queried have after the mnemonic Commands that MAY NOT be queried have no Do not send or as part of the command Th
165. e acquisition time divided by 512 7 8125 us at full span The positive limit of the delay is 65000 samples When the delay is negative the delay resolution is one sample of the A D conversion or 3 9062 us The limit of the negative delay is 13300 51 95 ms samples The time readout below the entry field is the equivalent delay in units of time Remember changing the frequency span will change the positive delay times 4 23 INPUT Arming Menu Return because the time record and sample times change The negative delays are not affected by the span When a large trigger delay is used the display may update slower since the acquisition time for each record is the length of the time record plus the trigger delay which can be noticeably long This key displays the Arming configuration menu as described on the following page This key returns to the main Input menu 4 24 INPUT MENU E Arming The Arming submenu selects the arming mode Arming Mode Auto wan Arm Trigger Trigger Menu Arming Mode mn Return Return Arming Mode This key selects the Arming Mode Triggers are ignored unless the trigger is armed Arming allows a single triggered time record to be isolated even when using a repetitive trigger source Auto arming means that as soon as one triggered time record is processed the trigger is immediately re armed Time records are basically take
166. e amplitude accuracy and frequency response Setup We will use the frequency synthesizer to provide an accurate frequency and the AC calibrator to provide a sine wave with an exact amplitude Connect the output of the frequency synthesizer to the phase lock input of the calibrator Connect the output of the AC calibrator to the A input of the analyzer Be sure to use the appropriate terminations where required Set the Synthesizer to Set the AC Calibrator to Function Sine Frequency 1 kHz Frequency 1 kHz Amplitude 0 707 mVrms Amplitude 0 5 Vrms Voltage Off Offset off or OV Phase Lock On Sweep off Sense Internal Modulation none Procedure 1 PRESET Turn the analyzer off and on with the lt key pressed 2 Press the keys in the following sequence MEAS Window lt Flattop gt FREQ lt Span gt 1 L 5 lt kHz gt lt Center Freq gt 1 kHz AVERAGE Number of Averages 2 0 Enter lt Averaging gt Select On 3 Amplitude accuracy is verified at 1 kHz and various input ranges For each range setting in the table below perform steps 3a through 3d Input Range pk AC Calibrator Amplitude 46 dBV 2 509 mVrms 38 dBV 6 302 mVrms 30 dBV 15 830 mVrms 14 dBV 99 881 mVrms 4 dBV 0 7934 Vrms 10 dBV 1 5830 Vrms a Set the AC calibrator to the amplitude shown in the table 6 8 ee PERFORMANCE TESTS MEN b Press Input lt Input Range gt Enter the range from the table c Press START
167. e center of the graph To set the graph to specific range use the YDIV command first to set the scale then either TREF or BREF to set the location This way the final graph does not depend upon the marker location The EXPD command sets or queries the X expansion for trace g The parameter i selects no expansion 155 or 128 i 4 65 i 3 30 1 2 15 i21 or 8 i20 bins across the graph The ELFT command sets or queries the left most displayed bin when X scale expansion is on The parameter 0 O i 1 392 is the bin number of the left most bin The maximum value of i is determined by the expansion number of bins across the graph and the highest bin number 399 If a value of i is sent which is outside the allowed range then the graph will either start at bin O or end at bin 399 The XAXS command sets or queries the X axis scaling type The parameter i selects Linear i20 or Log i71 5 9 ARMM 2 i The ARMM command sets or queries the trigger arming mode The parameter i selects Auto Arming i 0 or Manual Arming i 1 ARMS The ARMS manually arms the trigger when the arming mode is manual ee REMOTE PROGRAMMING 5 11 REMOTE PROGRAMMING ANALYSIS COMMANDS i CALC The ANAM command sets or queries the real time analysis mode for trace g The parameter i selects No Analysis i 0 Harmonic Analysis i 1 Sideband Analysis i 2 Band Analysis i 3 The CALC co
168. e enough to ensure that all harmonics are correctly identified This key activates the of Harmonics entry field Harmonics up to 400 may be entered though only those which are in the frequency span will enter into the harmonic calculations and be identified on the graph If 0 harmonics are entered the harmonic level readout will be zero This function moves the marker to the next harmonic to the left of the current marker position if it is on the graph If it is beyond the edge of the graph the 4 31 ANALYZE MENU Next Harmonic Right Return span center frequency is set to the frequency of the next harmonic or as close as the frequency range allows This function moves the marker to the next harmonic to the right of the current marker position if it is on the graph If it is beyond the edge of the graph the span center frequency is set to the frequency of the next harmonic or as close as the frequency range allows This key returns to the main Analyze menu 4 32 en ANALYZE MENU EHI Sideband Carrier 10 0000 kHz Separation 60 000 Hz SideBands Carrier Separation The Sideband analysis submenu turns on real time sideband analysis and sets the carrier and separation frequencies and number of number of sidebands ANALYZE Sideband Carrier Separation SideBands Return Sidebands are identified according to the formula Sideband Carrier neSeparation where n
169. e two data traces being acquired at all frequency or time on the X axis The physical size times The traces are labelled 0 and 1 1 of the graph remains constant while the vertical and The traces may be different measurements such horizontal scales may be changed The graph area as spectrum and time record or different displays has a dotted grid for reference There are 10 such as magnitude and phase When the two horizontal divisions and either 8 10 vertical traces are displaying live data they have the same divisions The frequency span consists of 400 signal input frequency span window function frequency bins The display normally shows all 400 trigger and averaging mode If one of the traces is a bins The X axis may be expanded and translated to recalled file then it can have a span and window display less than 400 bins This expansion does not which differs from the live settings change the span or time record it merely changes the display of the data The display shown above is the SINGLE trace format The ACTIVE TRACE key toggles the display between the two traces 3 4 12 5 kHz Y 13 21 dbV 0 kHz 50 kHz Top 20 dbV 20 dB div Wndo BMH File Live 25 0 kHz Y 100 2 dbV 0 50 kHz Top 2 dbV 20 dB div Wndo BMH File Live RUN uum The dual trace Up Dn format is shown above The display format is selected in the DISPLAY menu TraceO is always the upper trace Each trace i
170. e variables are defined as follows g trace number 0 1 Trace1 1 Active Trace i j integers real numbers f frequency 5 string All numeric variables may be expressed in integer floating point or exponential formats i e the number five can be either 5 5 0 or 5E1 Strings are sent as a sequence of ASCII characters NOTE All responses are directed to the interface selected in the Setup Communications Output To RS232 GPIB function regardless of which interface received the query Use the OUTP command to select the correct interface at the beginning of every program NOTE set command with a g parameter equal to 0 or 1 will make traceO or trace1 the active trace first then set the desired parameter A query command will not switch the active trace For example if the active trace is the MEAS 1 1 command will make trace1 the active graph and set its measurement type to PSD If the active trace is the MEAS 1 query will return the measurement type for trace1 without changing the active trace 5 3 REMOTE PROGRAMMING FREQUENCY COMMANDS The frequency and octave commands set or query the live settings The span of a recalled or stopped invalid trace is not queried by these commands The frequency span commands SPAN STRF and CTRF should be used if the measurement type is not octave analysis for either trace If either trace is measuring octaves then t
171. ector Female DESCRIPTION Power Entry Hardware Nut Kep Nut Kep Standoff Termination Tie Washer lock Wire 26 UL1061 Wire 24 UL1007 Strip 1 4x1 4 Tin Wire 24 UL1007 Strip 1 4x1 4 Tin Wire 18 UL1007 Stripped 3 8x3 8 No Tin Wire 24 UL1007 Strip 1 4x1 4 Tin Wire 24 UL1007 Strip 1 4x1 4 Tin Screw Flathead Phillips Screw Roundhead Phillips Screw Panhead Phillips Spacer Screw Panhead Phillips Screw Flathead Phillips Screw Panhead Phillips Washer nylon Screw Panhead Phillips Screw Black All Types Washer nylon Hardware Misc Screw Panhead Phillips Nut Hex Wire 18 UL1007 Stripped 3 8x3 8 No Tin Standoff Hardware Misc Screw Sheet Metal Screw Sheet Metal Screw Roundhead Phillips Power Button Screw Sheet Metal Wire 24 UL1007 Strip 1 4x1 4 Tin Wire 24 UL1007 Strip 1 4x1 4 Tin Wire 24 UL1007 Strip 1 4x1 4 Tin Hardware Misc Knobs Knobs Hardware Misc 7 28 eee PARTS LIST EMEN REF 20 20 20 20 20 SRS PART 0 00389 000 0 00390 024 0 00391 010 0 00394 031 0 00415 031 0 00416 020 0 00417 057 0 00418 000 0 00443 000 0 00466 050 0 00467 050 0 00500 000 0 00521 048 0 00527 050 0 00893 026 1 00033 113 1 00073 120 1 00076 171 1 00110 130 1 00120 113 1 00131 171 1 00132 171 1 00138 130 1 00141 171 1 00153 113 1 00167 169 1 00168 169 1 00180 170 1 00183 171 2 00023 218 2 00034 220 2 00035 222 4 00541 435 4 00649 455 4 00681 436 5 00134 529
172. ed line may be entered using the numeric keypad No knob adjustment is allowed Remember these values are simply numbers and have no units It is the user s responsibility to ensure that these values correspond to the displayed units This function selects the type of limit either upper or lower for the highlighted line This function displays a submenu for inserting or deleting lines turning on the audio alarm and enabling testing This submenu is described on the following pages This key returns to the main Analyze menu 4 43 ANALYZE MENU Limit Table More This submenu allows limit table entries to be inserted and deleted and audio alarms and limit testing to be enabled ANALYZE Limit Table Insert Item This function inserts a new line before the highlighted line The new line becomes highlighted and is ready for editing Delete Item This function deletes the highlighted line and highlights the following line Delete Table This function deletes the entire table Audio Alarm On Off This function turns the audio alarm on and off The audio alarm sounds whenever a limit test fails Testing On Off This function turns limit testing on and off Limit tests may be turned off while entering a table Limit testing is only active when the limit table is displayed regardless of this setting Return This key returns to the main Limit Table menu 4 44 een AVERAGE MENU Average Averaging
173. eed 400 CALL IBEOS SR770 V turn off terminate on EOS function so that we can read binary data 410 WRT speb 0 send the binary read command 420 CNT 800 we want to read 800 bytes 400 points 430 CALL IBWRT SR770 WRT 440 CALL IBRDI SR77096 BINARY96 0 CNT96 automatically reads all 800 points for us 445 450 DIM DBS 400 dimension an array to hold the db data 460 FOR 150 TO 399 STEP 1 470 19856 114 3914 3 0103 1 512 convert the binary data into db full scale 480 PRINT DBS I and print it 490 NEXT 500 510 INPUT for keypress 520 530 now we query the input range to get absoulte dBVs 540 550 WRT IRNG query the input range 560 GOSUB 780 570 S SPACE 20 580 CALL IBRD SR770 S get the answer 590 IRNG VAL S 600 FOR I 0 TO 399 STEP 1 610 13560 DBS l add the range to the dbfull scale values to get dBV 620 PRINT 630 NEXT 640 INPUT I waitfor keypress 650 660 alternatively we can use the spec command to obtain the spectrum in ascii form 1 point at a time 670 680 FOR 0 TO 399 STEP 1 690 WRT spec 0 STR I construct the command for each point 700 GOSUB 780 710 S SPACE 20 720 CALL IBRD SR770 S read the point 730 PRINT 155 740 NEXT I 750 STOP 770 PRINT Cannot find the SR770 gpib error 770 STOP 780 CALL IBWRT SR77096 WRT send a command to the sr770 790 CALL IBRSP S
174. egister to the decimal value i 0 255 ESR i 5 24 Query the Standard Status Byte If i is included only bit i is queried SRE i Gi 5 24 Set Query the Serial Poll Enable Register to the decimal value i 0 255 STB i 5 24 Query the Serial Poll Status Byte If i is included only bit i is queried PSC i 5 24 Set Query the Power On Status Clear bit to Set 1 or Clear 0 ERRE i 0 5 24 Set Query the Error Status Enable Register to the decimal value i 0 255 ERRS i 5 24 Query the Error Status Byte If i is included only bit i is queried FFTE i j 5 24 Set Query the FFT Status Enable Register to the decimal value i 0 255 FFTS i 5 24 Query the FFT Status Byte If i is included only bit i is queried STATUS BYTE DEFINITIONS SERIAL POLL STATUS BYTE 5 25 FFT STATUS BYTE 5 27 bit name usage bit name usage 0 SCN No measurements in progress Triggered Set when a time record is triggered 1 IFC No command execution in progress 1 Prn PIt Set when a printout or plot is completed 2 ERR Unmasked bit in error status byte set 2 NewDataO Set when new data is available for trace 0 3 FFT Unmasked bit in FFT status byte set 3 NewData1 Set when new data is available for trace 1 4 The interface output buffer is non empty 4 Avg Set when a linear average is completed 5 ESB Unmasked bit in standard status byte 5 AutoRng Set when auto range changes the range set 6 High Voltage Set w
175. egrated Circuit Thru hole Pkg U 608 3 00044 340 74HC244 Integrated Circuit Thru hole Pkg U 609 3 00046 340 74HC374 Integrated Circuit Thru hole Pkg U 610 3 00049 340 7AHC74 Integrated Circuit Thru hole Pkg U 611 3 00049 340 7AHC74 Integrated Circuit Thru hole Pkg U 612 3 00039 340 7AHC14 Integrated Circuit Thru hole Pkg U 701 3 00051 340 74HCU04 Integrated Circuit Thru hole Pkg U 702 3 00900 340 DS12C887 Integrated Circuit Thru hole Pkg U 703 3 00300 340 7415374 Integrated Circuit Thru hole Pkg U 704 3 00263 340 DS75451N Integrated Circuit Thru hole Pkg U 705 3 00110 340 1489 Integrated Circuit Thru hole Pkg U 801 3 00051 340 74HCU04 Integrated Circuit Thru hole Pkg U 802 3 00171 340 74HC191 Integrated Circuit Thru hole Pkg U 803 3 00277 340 74HC11 Integrated Circuit Thru hole Pkg U 804 3 00351 340 74 299 Integrated Circuit Thru hole Pkg U 805 3 00280 340 74HC10 Integrated Circuit Thru hole Pkg 7 12 eee PARTS LIST EMEN REF U 806 U 807 U 808 U 809 U 810 U 811 U 812 U 813 U 814 U 815 U 901 U 902 U 903 U 904 U 905 U 906 U 907 U 908 X 101 X 801 X 901 X 902 SRS PART 3 00049 340 3 00274 340 3 00303 340 3 00351 340 3 00598 340 3 00046 340 3 00046 340 3 00299 341 3 00299 341 3 00262 340 3 00350 340 3 00645 340 3 00078 340 3 00079 340 3 00247 340 3 00109 340 3 00596 360 3 00040 340 6 00068 620 6 00069 620 6 00068 620 6 00037 620 0 00126 053 0 00479 055 1 0
176. em Their function is determined by the label and does not change Hardkeys are referenced by brackets like this HARDKEY The softkeys are the six gray keys along the right edge of the screen Their function is labelled by a menu box displayed on the screen next to the key Softkey functions change depending upon the situation Softkeys will be referenced as the lt Soft Key gt or simply the Soft Key 1 31 The Measurement This measurement is designed to familiarize the user with the source capabilities We will use the SR770 Source to provide a test signal Specifically you will measure the spectrum of each of the source types taking advantage of the fact that the built in source is synchronous with the FFT ENN GETTING STARTED ee 1 32 eee GETTING STARTED EN USING THE SINE SOURCE 1 Turn the analyzer on while holding down the lt backspace key Wait until the power on When the power is turned on with the backspace key depressed the analyzer returns to its default tests are completed input Press SOURCE Press lt Sine gt Press lt Configure Source gt Press lt Level gt Press 3 lt dBV gt Press MARKER MAX MIN 4 Press lt Frequency gt Use the knob to adjust the frequency to 50 00 kHz Press MARKER MAX MIN Press lt Frequency gt Press 5 0 0 1 lt kHz gt Use the knob to adjust the frequency to 10 kHz Connect the SR770 Source output to the A se
177. ency to 10 1 kHz This is NOT an exact bin frequency Note that the signal peak is Press lt Frequency gt dramatically affected in both amplitude and frequency width This is because this frequency is Press 1 0 1 lt kHz gt not periodic in the time record The end points of the time record are not equal and represent a large step discontinuity The spectrum of this discontinuity is spread over the entire spectrum Display the Measure menu Choose the Window menu Press MEAS Choose a non uniform window The window function allows the non periodic signal to be analyzed Note Press lt Window Menu gt that the signal peak frequency is reported as 10 00 kHz even though the signal is at 10 1 kHz This is Press lt BMH gt because the FFT only results in 400 discrete frequency bins The signal peak is also wider than with the uniform window Windows decrease the selectivity of the spectrum by widening the signal peaks The amplitude of the peak is also wrong This is because window functions have amplitude variations for signals between bins All in all the sine source should be used with an exact bin frequency whenever possible This allows source triggering no jitter trigger regardless of signal to noise ratio and vector averaging as well as eliminating window effects 1 36 eee GETTING STARTED EN USING THE TWO TONE SOURCE 1 Turn the analyzer on while holding down the lt backspace key Wait until the pow
178. ency will be entered into the carrier frequency entry field If any real time analysis is already on then this key simply displays the sideband analysis submenu without change The sideband submenu is described in the following pages When sideband analysis is on the sideband level rms sum of the magnitudes of the sideband frequency bins and sideband level relative to carrier in dBc are displayed in the upper left corner of the graph Only those sidebands which appear within the frequency span figure into the calculations of sideband power If no real time analysis is on then this key turns on band analysis for the active trace The band analysis submenu is displayed and the marker frequency will be entered into the band center frequency entry field The band start will be adjusted consistent with the band width If any real time analysis is already on then this key simply displays the band analysis submenu without change The band submenu is described in the following pages When band analysis is on the band level rms sum of the magnitudes of all frequency bins within the defined band is displayed in the upper left corner of the graph Only the portion of the band which is within the frequency span contributes to the calculation of band level This key turns on the data table for the active trace and displays the data table submenu which is described in the following pages The screen format will switch to the dual trace mode and the i
179. enter frequencies This is because these frequencies are always exact frequency bins or multiples of the linewidth Larger spans have larger linewidths and thus the start and stop frequencies may need to be rounded to the nearest allowable bin of the new span 4 2 nen MEASURE MENU EN Measure Measure Menu Display Menu Units Menu Window Menu Calculator Menu Measure Keys The Measure menu is used to select the measurement type display type units and window function The Measure menu also activates the calculator for trace math Calculator Each Measure Key activates a sub menu Each sub menu is described in detail in the following pages 4 3 MEASURE MENU M Measure Spectrum Time Record Octave Ana Return Spectrum PSD The Measure sub menu selects the type of measurement for the active trace Time Record Octave Analysis Starting Band Weighting The SR770 filters the input data in real time to provide a time record with the desired frequency span and then performs an FFT on this record Pressing the Spectrum key displays this FFT on the active trace The PSD or Power Spectral Density is the magnitude of the spectrum the square root of the FFT times its complex conjugate normalized to a bandwidth of 1 Hz This measurement approximates the amplitude within a 1 Hz bandwidth located at each frequency bin The actual line
180. er on tests are completed 2 Connect the SR770 Source output to the A input Press SOURCE Press lt 2 Tone gt Press AUTO RANGE Press MARKER MAX MIN 3 Press lt Configure Source gt Press lt Frequency 1 gt Use the knob to adjust the frequency to 10 kHz 4 Press MARKER MAX MIN Press MARKER CENTER When the power is turned on with the backspace key depressed the analyzer returns to its default settings See the Default Settings list in the Menu section for a complete listing of the settings Display the Source menu Turn on the Sine output Let the analyzer select the input range The spectrum has two equal signal peaks at 1 kHz and 9 kHz The two tone source is simply the sum of two sine waves Each tone has its own amplitude and frequency which are adjusted in the same manner as the single sine Display the frequency and level of each tone Select the frequency of tone 1 When the knob is used to adjust the tone frequency the frequency resolution is equal to the linewidth of the displayed spectrum In this case since we are at full span the linewidth is 250 Hz 100 kHz 400 This always puts the tone exactly on a frequency bin of the spectrum The keypad allows random frequencies to be entered The fundamental frequency resolution of the sine is 15 26 mHz The entered frequency will be rounded to the nearest multiple of 15 26 mHz Generally the tone frequency should be an exact bin frequency
181. er to the National Instruments manual for information In this example the following options must be set with IBCONF Device name fft770 Device address 10 EOS character OAH linefeed Terminate Read on EOS Yes Once all the hardware and GPIB drivers are configured use IBIC This terminal emulation program allows you to send commands to the SR770 directly from your computer s keyboard If you cannot talk to the SR770 via IBIC then your programs will not run Use the simple commands provided by National Instruments Use IBWRT and IBRD to write and read from the SR770 After you are familiar with these simple commands you can explore more complex programming commands aere oc UO S oe OS ON Nee eee COO opener Example program using Microsoft C V5 1 and the National Instruments GPIB card This program assumes that the SR770 is installed as device fft770 using IBCONF include lt stdio h gt include lt dos h gt include lt conio h gt include lt stdlib h gt include lt string h gt include decl h function prototypes void main void int ibfind char void ibwrt int char int void ibrd int char int void ibrsp int char void ibeos int int void txsr770 char 5 31 REMOTE PROGRAMMING global variables int sr770 device identifier for the sr770 int rxBuff 400 buffer for binary data from sr770 double
182. eraging and smoothes out window variations Typically time records with 50 overlap provide almost as much noise reduction as non overlapping time records when RMS averaging is used When RMS averaging narrow spans this can reduce the measurement time by 2 Overlap percentage The amount of overlap is specified as a percentage of the time record 0 is no overlap and 99 8 is the maximum 511 out of 512 samples re used The maximum overlap is determined by the amount of time it takes to calculate an FFT and the length of the time record and thus varies according to the span The SR770 always tries to use the maximum amount of overlap possible This keeps the display updating as fast as possible Whenever a new frequency span is selected the overlap is set to the maximum possible value for that span If less overlap is desired then use the Average menu to enter a smaller value On the widest spans 25 50 and 100 kHz no overlap is allowed Triggering If the measurement is triggered then overlap is ignored Time records start with the trigger The analyzer must be in continuous trigger mode to use overlap processing een ANALYZERBASICS INPUT RANGE The input range on the 5 770 varies from a maximum of 34 dBV full scale to a minimum of 60 dBV full scale A signal which exceeds the current input range will cause the OvrLoad message to appear at the bottom of the screen A signal which exceeds the maximum safe range
183. erent functions depending upon the information displayed in the menu boxes along the right edge of the screen In general the softkeys have two uses The first is to toggle a feature on and off or to choose between settings The second is to highlight a parameter which is then changed using the knob or numeric keypad In both cases the softkeys affect the parameters which are displayed adjacent to them Softkeys are referenced in brackets like lt Span gt Knob The knob is used to adjust parameters which have been highlighted using the softkeys Most numeric 6 1 entry fields may be adjusted using the knob In addition functions such as display zooming and scrolling use the knob as well In these cases the knob function is selected by the softkeys The MARKER key which can be pressed at any time will set the knob function to scrolling the marker Preset Throughout this section it will be necessary to preset the analyzer into a known default state To do this turn the power off Turn the power back on while holding down the lt backspace key The unit will perform power up tests and then assume the default settings Each test generally starts with a preset This procedure will be referred to as PRESET Serial Number If you need to contact Stanford Research Systems please have the serial number of your unit available The serial number is printed on a label affixed to the rear panel The serial number is als
184. es the graph 4 83 STORE RECALL MENU ee 4 84 en DEFAULT SETTINGS If the lt backspace key is held down when the power is turned on the analyzer settings will be set to the defaults shown below rather than the settings that were in effect when the power was turned off The default settings may also be recalled using the RST command over the computer interface In this case the communications parameters and status registers are not changed ACTIVE TRACE ANALYZER AUTO RANGE FREQUENCY Span Linewidth Acq Time Start Freq Center Freq MEASURE Measurement Display Units Window Calculator Operation Argument Type Argument DISPLAY Format Marker Marker Width Marker Seeks Grid Graph Style INPUT Input Source Grounding Coupling Input Range Trigger Trigger Level Trigger Slope Trigger Delay Arming Mode Auto Offset SCALE Top Reference Bottom Reference Y Div Expand X 0 Running Off Manual Range 100 kHz 250 Hz 4ms 0 0 Hz 50 0 kHz Spectrum Log Mag dBVolts BMH Constant 0 0 Single On Norm Max 8 divisions Line A Float AC 0 dBV Continuous 0 00 Positive 0 Auto On 20 140 20 None X Axis ANALYZE Analysis Type AVERAGE Averaging Number of Averages Average Type Average Mode Overlap SOURCE Type Sine Frequency Sine Level Tone Freq 1 Tone Level 1 Tone Freq 2 Tone Level 2 Noise Type Noise Level Chirp Level Source C
185. espite wide temperature variations As such the anti aliasing filter used in the SR770 does not ever require calibration to meets its specifications Following the anti aliasing filter is a gain stage to buffer the output of the filter and to provide a small amount of gain before going to the A D Converter To minimize offset 8 bit DAC U307 provides an offset voltage to compensate for offsets accumulated in the gain stages U309 sends the output of the filter to the DSP Logic Board for internal triggering purposes Diodes D301 D304 provide input protection for the A D converter 7 8 A D CONVERTER The A D Converter converts the final signal to a digital data stream Conversion takes place at a rate of 256 000 samples per second A Burr Brown PCM1750 18 bit A D Converter is used for this purpose INTERFACE The Analog Input Board communicates with the CPU Board via its I O Interface IC s U504 U506 form a 24 bit shift register and latch Data is shifted in serially from the CPU Board and latched to internal latches The outputs of the latches are used to control relays switches etc U503 opto isolates the signals for the shift registers to prevent DSP Logic Board Noise from entering the Analog Input Board Timing signals for the A D Converter are received via pulse transformers T501 T503 configured as common mode rejection transformers to isolate the analog and digital grounds POWER Several voltages are generated on
186. f the X axis are the frequencies of the actual signal not the heterodyned frequencies Heterodyning allows the analyzer to compute zoomed spectra spans which start at frequencies other than dc The digital filter processor can filter and heterodyne the input in real time to provide the appropriate filtered time record at all spans and center frequencies Because the digital signal processors in the SR770 are so fast you won t notice any calculation time while taking spectra The longest it can take to acquire a spectrum is the length of the time record itself But more about that later en ANALYZERBASICS THE TIME RECORD Now that we ve described the process in simple terms let s complicate it a little bit The SR770 actually uses 512 point complex time records Each point is a complex value with real and imaginary parts so the record actually has 1024 data points in it But how does a real point get to be complex As we described in the previous section the input samples are digitally filtered and heterodyned to produce a time record with the appropriate bandwidth and a constant number of samples What we need to add to this is that the heterodyning is a complex operation This means that the input points are multiplied by both sine and cosine to yield a real and imaginary part So instead of using 1024 real points we use 512 complex points The time records have the same duration so the complex record has half the sa
187. fer curve of the device This is similar to a ratio measurement using a 2 channel analyzer except that the output ripple is measured at the factory and is not adjustable by the user Remember the Source Cal mode compensates for variations in the output spectrum by adjusting the input calibrations The actual signal at the Source Output is not affected Source Cal has NO effect unless the source is Chirp or Noise Source Cal can only be selected in the Configure Noise or Chirp submenu Do not select Source Cal On and use an external signal source The input calibrations are modified and will result in measurement errors unless the SR770 internal source is used as the test signal This key returns the main source selection menu 4 57 SYSTEM MENU System Setup Commun Setup Sound Setup Time Print More ore System Keys The System menu is used to configure the printer plotter and computer interfaces and to set the screen sound and clock calendar parameters The Test submenu accesses various hardware tests The Info submenu displays various information screens which may be useful to the user Setup Screen Test Hardware cj Get Info SYSTEM Test Hardware Get Info The System menu consists of two menus with each key activating a submenu Use the More and Return softkeys to toggle between the two menus 4 58 en SYSTEM MENU Setup Communications Co
188. he MARKER REF key toggles the marker offset or reference mode Pressing this key once will turn on the marker offset and set the X and Y offset to the value of the current marker position Subsequent marker readings are relative to the reference or offset values The offset marker is indicated by ali delta symbol preceding the marker readout above the graph as shown below The MARKER REF key may be used in any menu y 12 5 kHz Y 13 21 dbV LogMag Spec The marker offset location on the graph is marked by a small star shaped symbol Mee OPERATION EN MARKER CENTER The MARKER CENTER key sets the span center frequency to the marker frequency If the span is large so that this operation would require a span which extends below 0 Hz or past 100 kHz then the span is decreased to the largest span which allows the marker frequency to be the center In addition the MARKER CENTER key has the same effect as the MARKER key The marker display is highlighted and the knob will adjust the marker position MARKER MAX MIN Pressing MARKER MAX MIN will center the marker region around the maximum or minimum data value on the screen The Marker Seeks mode in the DISPLAY menu chooses whether this key finds the on screen max or min If the marker seeks the mean then the MARKER MAX MIN key finds the maximum on screen point The marker will be positioned at the Min Max or Mean of the data within the region depending upon the seek
189. he frequency commands will result in an error SPAN 2 i STRF f CTRF f The SPAN command sets or queries the frequency span The parameter i selects a span as shown below i span i span 0 191 mHz 10 195 Hz 1 382 mHz 11 390 Hz 2 763 mHz 12 780 Hz 3 1 5 Hz 13 1 56 kHz 4 3 1 Hz 14 3 125 kHz 5 6 1 Hz 15 6 25 kHz 6 12 2 Hz 16 12 5 kHz 7 24 4 Hz 17 25 kHz 8 48 75 Hz 18 50 kHz 9 97 5 Hz 19 100 kHz The STRF command sets or queries the start frequency of the span The parameter f is a frequency real number of Hz The value of f will be rounded according to the resolution of the current span Values of f which would cause the span to exceed the 0 to 100 kHz range are set to the allowable value closest to f The CTRF command sets or queries the center frequency of the span The parameter f is a frequency real number of Hz The value of f will be rounded according to the resolution of the current span Values of f which would cause the span to exceed the 0 to 100 kHz range are set to the allowable value closest to f The octave commands OTYP OSTR and WTNG should be used if one of the traces is measuring octave analysis If neither trace is measuring octaves then the octave commands will result in an error OTYP i OSTR i WTNG i The OTYP command sets or queries the type of octave analysis The parameter i 0 selects 15 bands and i21 selects 30 bands The OSTR command sets or queries the
190. he reading is relative A small star symbol is located on the graph at the marker offset position Note that the distortion products are separated by 1 kHz increments from the two tone frequencies They should also be very small 80 dB relative to the tone amplitudes In this configuration it is not possible to determine whether the distortion exists at the source output or the signal input This measurement determines the sensitivity of any IMD measurement made using the two tone source 1 38 een GETTING STARTED EN USING THE NOISE SOURCE 1 Turn the analyzer on while holding down the lt backspace key Wait until the power on tests are completed 2 Connect the SR770 Source output to the A input Press SOURCE Press lt Noise gt Press AUTO RANGE 3 Press lt Configure Source gt Press lt Noise Level gt Press 1 0 0 lt mV gt Press 1 0 0 0 mV 4 Press INPUT Press lt Auto Offset gt to select Off Press AVERAGE Press lt Number of Averages gt Press 4 0 0 0 lt Enter gt Press lt Averaging gt to turn averaging on When the power is turned on with the backspace key depressed the analyzer returns to its default settings See the Default Settings list in the Menu section for a complete listing of the settings Display the Source menu Turn on the Noise output Let the analyzer select the input range The spectrum is flat noise from O to 100 kHz at a leve
191. hen high voltagedetected at input 6 SRQ SRQ service request has occurred 7 Settle Set when settling is complete 7 Unused ERROR STATUS BYTE 5 27 STANDARD EVENT STATUS BYTE 5 26 bit name usage bit name usage 0 Prn PltErr Set when an printing or plotting error 0 INP Set on input queue overflow occurs 1 Limit Fail Set when a limit test fails 1 Math Error Set when an internal math error occurs 2 QRY Set on output queue overflow 2 RAMError Set when RAM Memory test finds an error 3 Unused 3 Disk Error Set when a disk error occurs 4 EXE Set when command execution error 4 ROM Error Set when ROM Memory test finds an error occurs 5 A D Error Setwhen A D test finds an error 5 CMD Set when an illegal command 15 6 DSP Error Set when DSP test finds an error received 7 Overload Set when the signal input overloads 6 URQ Set by any key press or knob rotation 7 PON Set by power on xi 5 770 FFT SPECTRUM ANALYZER xii ee GETTING STARTED EN YOUR FIRST MEASUREMENT This sample measurement is designed to acquaint the first time user with the SR770 Network Analyzer Do not be concerned that your measurement does not exactly agree with this exercise The focus of this measurement exercise is to learn how to use the instrument There are two types of front panel keys which will be referenced in this section Hardkeys are those keys with labels printed on them Their function is determined by the label and does not change Hard
192. his window is especially useful in measurements requiring the more than 70 dB of dynamic range since it has the lowest leakage and broadening of the skirts MEASURE MENU M Return The Return key will return to the main MEAS menu 4 12 en MEASURE MENU EN Calculator Operation x og d dx Do Calc 5 Argu Ty Const Other Graph Argument Operation The Calculator sub menu allows user to perform arithmetic calculations with the trace data Operations are performed on the entire trace regardless of graphical expansion Calculations treat the data as intrinsic values either Volts EU or degrees radians If a graph is showing dB then multiplying by 10 will raise the graph by 20 dB and dividing by 10 will lower the graph by 20 dB Performing a calculation on the active trace will set the File Type to Calc to indicate that the trace is not Live This is shown by the File Calc message at the lower left of the graph The analyzer continues to run but the calculated trace will not be updated To return the trace to live mode activate the trace and press the START key The File Type will return to Live Argument Type The Operation function selects the type of operation to be performed The add subtract multiply and divide functions require a second argument which may be a number 26f or the other trace The log base 10 square root unwrap and d dx func
193. ible plotters via RS232 or 488 3 5 inch DOS compatible format 720 kbyte capacity Storage of data setups data tables and limit tables 60 Watts 100 120 220 240 VAC 50 60 Hz 17 W x 6 25 H x 18 5 D 36 Ibs One year parts and labor on materials and workmanship vii 5 770 FFT SPECTRUM ANALYZER COMMAND LIST VARIABLES FREQUENCY SPAN i STRF ff CTRF ff OTYP i OSTR i WTNG i MEASUREMENT MEAS g i DISP 9 0 UNIT i VOEU g 1 EULB g 3 EUVT 9 g 00 WNDO g i DISPLAY and MARKER ACTG 2 i FMTS 2 g 1 GRID g Li FILS 2 g i MRKR g Li Li MRKM 2 Li MRLK i MBIN 041 MRKX MRKY MRPK MRCN MRRF MROF i MROX 2 MROY 2 x PKLF PKRT MSGS s SCALE TREF g x BREF g x g xj AUTS g EXPD 2 g 1 ELFT 2 1 XAXS g Li 9 TraceO 0 Trace1 1 or Active Trace 1 i j Integers f Frequency real Real Numbers 5 String page description 5 4 Set Query the Frequency Span to 100 kHz 19 through 191 mHz 0 5 4 Set Query the Start Frequency to f Hz 5 4 Set Query the Center Frequency to f Hz 5 4 Set Query the number of bands in Octave Analysis to 15 0 or 30 1 5 4 Set Query the Starting Band in Octave Analysis to 2 lt i lt 35 5 4 Set Query the Weighting in Octave Analysis to non
194. ied and will result in measurement errors unless the SR770 internal source is used as the test signal The APHS command performs the Auto Phase function This command only has an effect when the noise source is chirp The NTYP command sets or queries the noise type The i selects white noise 150 or pink noise i1 5 16 ee REMOTE PROGRAMMING PRINT and PLOT COMMANDS PLOT PTRC PMRK PTTL s PSTL s PRSC PSET PLIM PDAT The PLOT command generates a plot of the entire screen Each feature uses the pen assigned in the Setup Plotter menu The marker is plotted only if the marker is on The PTRC command plots only the data trace s The PMRK command plots only the marker s if they are on The marker readout is plotted next to the marker The PTTL command sets or queries the plot title The string s is the title The PSTL command sets or queries the plot subtitle The string s is the subtitle The PRSC command will print the currently displayed screen to a printer attached to the rear panel parallel printer port This function is the same as the PRINT key The printer type needs to be configured before using the PRSC command The PSET command will print the analyzer settings to a printer attached to the rear panel parallel printer port The printer type needs to be configured before using the PSET command The PLIM command will print the limit table for the active trace to a printer att
195. ifier output may require a terminator Many instruments have either a 50 or 600 O output impedance Use the appropriate feedthrough termination if necessary In general not using a terminator means that the output amplitude will not agree with the instrument setting and the distortion may be greater than normal Display the Source menu Turn on the Sine output Display the sine configuration menu Highlight the Sine Output Level Leave the frequency at 1 kHz Enter 100 mV pk This should be a small enough signal for the amplifier to handle If not simply lower the sine output level to a suitable level Since the amplifier output amplitude may not be set accurately let the analyzer automatically set its input range to the actual signal Display the Frequency menu Set the span to display the 1 kHz signal and its first few harmonics Set the graph scaling to display the entire range of the data Move the marker to the signal peak 1 kHz The marker should read an amplitude equal to the source output level times the amplifier gain This turns on the marker offset and sets the reference marker to the current marker position From now on the marker will now read relative to Use the knob to move the marker to a region that is representative of the noise floor Press MARKER REF again Press MEAS Press lt Measure Menu gt Press lt PSD gt Press AVERAGE Press lt Average Mode gt Press lt Number of
196. igure Source gt to set the noise parameters Since the signal is noisy and random windows are always required when using the noise source Source triggering is not meaningful since there is no stable phase information in the source This key sets the source output to the chirp waveform The Chirp waveform provides an equal amplitude sine wave at each bin of the displayed spectrum Since there are 400 bins in a spectrum the chirp is the sum of 400 discrete sine waves The phases of each sine wave are arranged so that they do not add in phase and the resulting output does not peak This source is useful for measuring transfer functions quickly without having to make many discrete measurements using a single sine wave Press lt Configure Source gt to set the chirp parameters Each source has a configuration menu which is accessed by selecting the source type and then pressing the lt Configure Source gt key Each type of configuration menu is described in the following pages 4 51 SOURCE M Configure Sine Frequency Level 1000 mV Return Frequency Level Return The Configure Sine submenu allows the frequency and amplitude of the sinewave to be set SOURCE Configure Source This key activates the sine frequency entry field When the knob is used to adjust the frequency the resolution is equal to the linewidth of the measurement span The knob always sets the sine frequency to an exact
197. ile Name field Activating the cursor by pressing the MARKER key allows the knob to scroll through the directory The highlighted file name will be copied into the File Name field If the Save Data key is now pressed the data will be saved under an existing file name and the previous version of that file will be lost To create a new file name use the File Name key Directory entries made by the SR770 also have a type field shown in the catalog display Files with type SET are settings and type DAT are trace data The file type is not an extension but is information stored in the directory on the disk Only files created by the SR770 have a type Files created and saved on a DOS computer will not have a type displayed The file type is not necessary it is only an aid to identifying files The Return key will return to the main Store Recall menu Return also removes the catalog display screen and restores the graph 4 79 ENN STORE RECALL MENU ee Save Settings Save Settings File Name TEST Catalog On The Save Settings submenu is used to save the analyzer settings to a disk file The settings include all parameters which are set with the menus Save Settings File Name Catalog On Off Return Pressing this key will save the current analyzer settings to the file specified in the File Name field This key activates the File Name entry field File names are entered using the keypad and alternate keypa
198. in System Setup menu 4 68 en SYSTEM MENU EM Print Print Settings Print Limits Print Data Printer Type Epson File Return Print Settings Print Limits Print Data Printer Type The Print submenu is used to print the SR770 settings limit tables and data tables to a printer These printouts provide a convenient and accurate way to document measurements The PrinterType selects the type of printer The PRINT key prints the screen to the printer If File is chosen as the printer type then PRINT will save the screen image as a file on the disk SYSTEM The Print Settings key sends a listing the settings of the analyzer to the printer The settings listed are all those which are saved in non volatile memory and retained when power is turned off The Print Limits key sends a listing of the limit table for the active trace to the printer The listing is in the same format as the limit table display The Print Data key sends a listing of the data table for the active trace to the printer The data table is first updated with the current Y values The listing is in the same format as the data table display This function toggles the Printer Type between Epson HP and File Epson is used for any Epson compatible graphics dot matrix printer and HP is used for an HP LaserJet laser printer or compatible File is used to save the screen image as a file on the disk The files
199. in this section Hardkeys are those keys with labels printed on them Their function is determined by the label and does not change Hardkeys are referenced by brackets like this HARDKEY The softkeys are the six gray keys along the right edge of the screen Their function is labelled by a menu box displayed on the screen next to the key Softkey functions change depending upon the situation Softkeys will be referenced as the lt Soft Key gt or simply the Soft Key The Measurement This measurement is designed to investigate the trigger and time record You will need a function generator capable of providing a 100 us wide pulse at 250 Hz with an amplitude of 1 V The output should have a DC level of OV Specifically you will measure the output spectrum when the signal is triggered In addition the trigger delay will be used to delay the signal within the time record Make sure that you have read The Time Record in the Analyzer Basics section before trying this exercise eee GETTING STARTED EN TRIGGERING THE ANALYZER 1 Turn the analyzer on while holding down the lt backspace key Wait until the power on tests are completed 2 Turn on the generator and choose a pulsed output waveform Set the frequency to 250 Hz the pulse width to 100 us and the amplitude to approximately 1 Make sure that the DC level of the output is near OV Connect the generator s output to the A input of the analyzer 3 Press INPUT
200. indicator at the lower left corner of the display will stay on while the data settles This centers the marker more accurately The frequency of the signal can now be read with 244 mHz resolution This key adjusts the graph scale and top reference to display the entire range of the data You can press this key at any time to optimize the graph display Display the Analysis menu Select Harmonic analysis The menu displays the harmonic analysis menu Notice that the fundamental frequency first menu box has been set to the frequency of the marker We used a narrow span to get an accurate reading of the fundamental signal frequency We will use this measurement of the fundamental to accurately locate the harmonics The harmonic measurement readout at the upper left corner of the graph is under range because the span is not wide enough to include any harmonics This centers the span around the second harmonic approx 2 kHz You are now making an accurate measurement of the 2nd harmonic content of the signal ENN GETTING STARTED M Use the lt Next Harmonic Right gt and lt Next Harmonic Left gt keys to investigate the harmonics of the signal 13 Press FREQ 14 15 16 17 Press lt Full Span gt Press AUTO SCALE Press lt Start Freq gt Now adjust the span to 12 5 kHz using the lt Span gt key and knob the SPAN DOWN key or by entering the span numerically Press ANALYZE Press lt Har
201. ing s may be up to 30 characters long All characters are converted to upper case and spaces are ignored To embed a space in the string use the HEX value 10H 16 decimal or and underscore _ For example the MSGSHELLO_USER command will display the message HELLO USER on the screen 5 8 een REMOTE PROGRAMMING SCALE COMMANDS AUTS g TREF 7 g x BREF 7 x YDIV 2 g 0 EXPD 7 9 Gi ELFT 7 g i XAXS 2 g Gi The AUTS command performs the Auto Scale function on trace g This function is the same as pressing the AUTO SCALE key with trace g active The AUTS command affects the TREF BREF and YDIV parameters below The TREF command sets or queries the top reference for trace g The TREF g x command sets the top reference to x where x is a real number which is assigned the units of the display This command will also affect the bottom reference The BREF command sets or queries the bottom reference for trace g The BREF g x command sets the bottom reference to x where x is a real number which is assigned the units of the display This command will also affect the top reference The YDIV command sets or queries the vertical scale for trace g The YDIV g x command sets the vertical scale to x division where x is a real number which is assigned the units of the display This command will also affect the top and bottom reference The graph will be adjusted so that the marker Y position stays in th
202. input signal For baseband measurements when the start frequency of the span is 0 0 Hz the waveform will resemble the signal waveform with folding if magnitude is displayed The bandwidth will be limited by the anti alias filter and the digital filtering For zoomed measurements when the span start is not 0 0 Hz the displayed waveform will not closely resemble the input signal because of the heterodyning Why use the time record The time display can be useful in determining whether the time record is triggered properly If the analyzer is triggered either internally by the signal or externally with another pulse and the signal has a large component synchronous with the trigger then the time record should appear stationary on the display If the signal triggers randomly then the time display will jitter back and forth Watch out for windowing The time display is not windowed This means the time record which is displayed will be multiplied by the window function before the FFT is taken see Windowing later in this section Most window functions taper off to zero at the start and end of the time record If the transient signal occurs at the start of the time record the corresponding FFT may not show anything because the window function reduces the transient to zero Either use a Uniform window with transients or use the trigger delay to position the transient at the center of the time record Remember that the display on
203. io of the imaginary and real parts of each frequency component The phase is always relative to the start of the triggered time record Power Spectral Density or PSD The PSD is simply the magnitude of the spectrum normalized to a 1 Hz bandwidth This measurement approximates what the spectrum would look like if each frequency component were really a 1 Hz wide piece of the spectrum at each frequency bin What good is this When measuring broadband signals such as noise the amplitude of the 2 4 spectrum changes with the frequency span This is because the linewidth changes so the frequency bins have a different noise bandwidth The PSD on the other hand normalizes all measurements to a 1 Hz bandwidth and the noise spectrum becomes independent of the span This allows measurements with different spans to be compared If the noise is Gaussian in nature then the amount of noise amplitude in other bandwidths may approximated by scaling the PSD measurement by the square root of the bandwidth Thus the PSD is displayed in units of or dBV HHz Since the PSD uses the magnitude of the spectrum the PSD is a real quantity There is no real or imaginary part or phase Octave Analysis The magnitude of the normal spectrum measures the amplitudes within equally divided frequency bins Octave analysis computes the spectral amplitude within T3 octave bands The start and stop frequencies of each frequency bin are in the ratio
204. is a single dashed line The marker region moves to the left and to the right a single bin at a time 4 16 eee DISPLAY MENU NNI Marker Seeks Grid Div Scrn Graph Fill The marker searches the data points within the marker region for the maximum or minimum data value or calculates the mean of the region This key toggles between Max Min and Mean and only affects the active trace s marker When seeking minimum or maximum the marker is located at the minimum or maximum data point This allows peaks and valleys in the data to be read easily When seeking mean the X position of the marker is the center of the marker region and the Y position is the mean of the data within the region This function selects no grid or 8 or 10 vertical divisions per graph The grid is the set of dotted lines on the graph which mark each scale division This affects only the active trace graph The active trace can be selected to display the spectrum as the envelope of the X values line or to fill the solid region below the trace fill ENN MARKER MODE MENU Marker Mode Linked Markers Marker Offset Off X Offset Y Offset Next Peak Linked Markers Marker Offset X Offset The Marker Mode menu is activated with the Mode key in the Marker area of the keypad This menu is used to manually enter a marker offset as well as searching for peaks in the data MODE Next Peak Left Next Peak Right
205. is measurement is its resolution Because the time record is only 4 ms long the frequency resolution is only 250 Hz Suppose the signal has a frequency component at 260 Hz The FFT spectrum will detect this signal but place part of it in the 250 Hz point and part in the 500 Hz point One way to measure this signal accurately is to take a time record that is 1 260 or 3 846 ms long with 1024 evenly spaced samples Then the signal would land all in one frequency bin But this would require changing the sampling rate based upon the signal which you haven t measured yet Not a good solution In fact the way to measure the signal accurately is to lengthen the time record and change the span of the spectrum ANALYZER BASICS FREQUENCY SPANS Before we continue let s clarify a couple of points about our frequency span We just described how we arrived at a dc to 128 kHz frequency span using a 4 ms time record Because the signal passes through an anti aliasing filter at the input the entire frequency span is not useable The filter has a flat response from dc to 100 kHz and then rolls off steeply from 100 kHz to 128 kHz No filter can make a 90 dB transition instantly The range between 100 kHz and 128 kHz is therefore not useable and the actual displayed frequency span stops at 100 kHz There is also a frequency bin labelled O Hz or dc This bin actually covers the range from 0 Hz to 250 Hz the lowest measurable frequency and cont
206. is real time bandwidth Simply stated it is the frequency span whose corresponding time record exceeds the time it takes to compute the spectrum At this span and below it is possible to compute the spectra for every time record with no loss of data The spectra are computed in real time At larger spans some data samples will be lost while the FFT computations are in progress For all frequency spans the SR770 can compute the FFT in less time than it takes to acquire the time record Thus the real time bandwidth of the SR770 is 100 kHz This includes the real time digital filtering and heterodyning the FFT processing and averaging calculations The SR770 employs two digital signal processors to accomplish this The first collects the input samples filters and heterodynes them and stores a time record The second computes the FFT and averages the spectra Since both processors are working simultaneously no data is ever lost Averaging speed How can you take advantage of this Consider averaging Other analyzers typically have a real time bandwidth of around 4 kHz This means that even though the time record at 100 kHz span is only 4 ms the effective time record is 25 times longer due to processing overhead An analyzer with 4 kHz of real time bandwidth can only process about 10 spectra a second When averaging is on this usually slows down to about 5 spectra per second At this rate it s going to take a couple of minutes to d
207. isplayed in inverse Make the lower trace the active trace Go to the Measure menu Show the Display submenu Display the phase of the spectrum on the lower graph The phases of the frequency components of the chirp are stable but seemingly random To measure the phase response of a device under test we need to calibrate the phase of the source Go back to the Source menu Show the chirp output configuration menu The Auto Phase function measures the current phase spectrum This phase spectrum is stored in memory and subtracted from subsequent phase spectra to remove the phase of the chirp source The phase spectrum now shows 0 at all frequencies If a device under test is inserted between the source and the input the lower graph will show the phase response of the device Auto phase is removed when the span is changed or the source type is changed Change the span Back to 100 kHz span The phase calibration is removed whenever the 1 44 eee GETTING STARTED EN 6 Press DISPLAY Press Format to select Single 7 Press MEAS Press Calculator Menu Press Operation 6 times to select unwrap Press Do Calc Press Auto Scale 8 Press Operation to select d dx Press Do Calc Press 1 2596 9 Press Operation to select divide span is changed Remember if phase information is desired Auto Phase must be performed after every span change Auto Offset also di
208. ities The magnitude is the square root of the product of the measurement data and its complex conjugate This key displays the magnitude of the measurement on a scale Only the active trace display is affected Both the Time Record as defined in this analyzer and the corresponding FFT are complex quantities The magnitude is the square root of the product of the measurement data and its complex conjugate This key displays the real part of the measurement on a linear scale Only the active trace display is affected Both the Time Record as defined by the SR770 and the corresponding Spectrum are complex quantities and thus have a real part PSD and Octave Analysis are not complex and only display magnitudes This key displays the imaginary part of the measurement on a linear scale Only the active trace display is affected Both the Time Record as defined by the SR770 and the corresponding Spectrum are complex quantities and thus 4 7 MEASURE MENU Se Phase Return have an imaginary part PSD and Octave Analysis are not complex and only display magnitudes This key displays the phase of the measurement on a linear scale Only the active trace display is affected Both the Time Record as defined by the SR770 and the corresponding Spectrum are complex quantities and thus have phase PSD and Octave Analysis are not complex and only display magnitudes In general phase measurements are only used when the analyze
209. itudes are compared to the previous data and if the new data is larger then the new data is used This is done on a bin by bin basis The resulting display shows the peak magnitudes which occurred in the previous spectra If linear averaging is used then only N spectra are compared If exponential averaging is used then peak hold keeps comparing spectra indefinitely Peak Hold detects the peaks in the spectral magnitudes and only applies to Spectrum PSD and Octave Analysis measurements However the peak values are stored in the original complex form If the real or imaginary part or phase is being displayed for spectrum measurements the display shows the real or imaginary part or phase of the complex peak value This key selects either Linear or Exponential averaging Linear Averaging Linear averaging combines N number of averages spectra with equal weighting in either RMS Vector or Peak Hold fashion When the number of 4 46 en AVERAGE MENU EN averages has been completed the analyzer stops and an audio beep is sounded When linear averaging is in progress the number of averages completed so far is displayed below the Avrging indicator at the bottom of the Screen Auto ranging is temporarily disabled when a linear average is in progress Be sure not to change the input range manually either Changing the range during a linear average invalidates the results Exponential Averaging Exponential averaging weights new data more
210. ive trace data in ASCII format Only the trace data is saved The data is saved as 0 00 1 23 cr If 1 00e3 4 56 cr If 2 0063 7 89 cr lt gt where 0 00 1 23 is the frequency or time and data point for the first bin 1 00e3 4 56 is the frequency or time and data point for the second bin etc for a total of 400 bins 15 or 30 bins in octave analysis The data assumes the units of the current display The ASCII format is a convenient way to transfer data to other programs on a PC The file is a simple DOS text file This key activates the File Name entry field File names are entered using the keypad and alternate keypad The ALT key allows letters to be entered DOS file name conventions must be followed i e file names are 8 characters or less with an extension of up to 3 characters ABCDEFGH XYZ is a valid file name DOS sub directories are not supported Catalog On Off Type Size All files are saved to the root directory This key toggles the file catalog display screen on and off The file catalog display lists all files currently in the root directory A sample catalog screen is shown below Date Time ABCD DAT DAT TEST Spect1 SET DAT MyData bak DAT 4 47 28 09 21 41 11 21 01 02 22 91 03 13 91 04 11 91 ABCD DAT Catalog Free 720280 bytes Den STORE RECALL MENU Return The first file will be highlighted and the file name will appear in the F
211. kage Transistor TO 92 Package Transistor TO 92 Package Transistor TO 92 Package Resistor 2W 1 Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 AW 5 Resistor Metal Film 1 8W 1 50PPM 7 23 EN PARTS LST REF R 132 R 133 R 134 R 135 R 136 R 137 R 138 R 139 R 140 R 141 R 142 R 143 R 144 R 146 R 147 R 148 R 149 R 201 R 202 R 203 R 204 R 205 R 206 R 207 R
212. keys are referenced by brackets like this HARDKEY The softkeys are the six gray keys along the right edge of the screen Their function is labelled by a menu box displayed on the screen next to the key Softkey functions change depending upon the situation Softkeys will be referenced as the lt Soft Key gt or simply the Soft Key Hardkeys The keypad consists of five groups of hardkeys The ENTRY keys are used to enter numeric parameters which have been highlighted by a softkey The MENU keys select a menu of softkeys Pressing a menu key will change the menu boxes which are displayed next to the softkeys Each menu groups together similar parameters and functions The CONTROL keys start and stop actual data acquisition select the marker and toggle the active trace the display These keys are not in a menu since they are used frequently while displaying any menu The SYSTEM keys output the screen to a printer and display help messages These keys can also be accessed from any menu The MARKER keys determine the marker mode and perform various marker functions The marker functions can be accessed from any menu Softkeys 1 1 The SR770 has a menu driven user interface The 6 softkeys to the right of the video display have different functions depending upon the information displayed in the menu boxes at the right of the video display In general the softkeys have two uses The first is to toggle a feature on and off or to choose
213. l of approximately 30 dBV The input range has auto ranged to a much higher level around 4dBV This is because the peak output voltage is greater than 1 V Display the noise configuration menu Select the noise level The noise level is approximately the peak amplitude of the noise output There will be occasional voltage excursions beyond this level Because of the nature of noise the peak amplitude is not a well defined quantity Enter a noise level of 100 mV This lowers the noise spectrum by 20 dB Restore the noise level back to 1000 mV Display the Input menu Turn off Auto Offset before we start averaging Display the Average menu Highlight the number of averages Enter 4000 averages Turn averaging on and wait until the average is complete In Linear average mode at the end of 4000 averages the analyzer will stop Notice how the noise has averaged to a stable 1 39 ENN GETTING STARTED M Press AUTO SCALE 5 Press MEAS Press lt Measure Menu gt Press lt PSD gt Press AUTO SCALE Press MARKER Use the knob to center the marker at 50 kHz value RMS averaging averages the magnitude of the signal and reduces the fluctuations in the data Note that the noise spectrum is flat Change the display scale so that the fluctuations in the spectral flatness are visible The noise output spectrum covers 0 to 100 kHz regardless of the analysis span The source is digitally synthesized and passes
214. l trigger this means that the signal must exceed roughly 8 of the input range 22 dB below the input range Note When the unit is successfully triggered in Int TTL or Ext mode the Trigger indicator will light No indicator is present in the Continuous or Source trigger mode When the analyzer is in Int TTL or Ext trigger mode and no triggers are received the display will not update even though the RUN indicator is on When no triggers have been received after a couple of seconds the Trg Wait indicator will turn on as a reminder that the unit is awaiting a trigger In Int TTL or Ext trigger mode the unit will trigger only if the trigger is armed See the Arming menu This key toggles the Trigger Slope between rising edge and falling edge nt TTL and Ext trigger modes only This key activates the Trigger Delay entry field TTL and Ext trigger modes only The delay may be entered numerically or adjusted using the knob The delay is set as a number of samples rather than time The Source trigger does not have an adjustable delay The triggered time record does not have to start with the trigger event The time record can start before the trigger negative delay values or after the trigger positive delay values A delay of 0 starts the time record with the next sample following the trigger When the delay is positive the delay is set with a resolution of one sample or 1 512 of the time record This is equal to th
215. layed The result of the limit test is shown by the Pass Fail indicator at the bottom of the screen In addition an audio alarm may be sounded Each displayed trace is tested The limit testing may be turned off while in the Limit menu It is recommended that testing be turned off while entering a complex table since live testing can slow the analyzer response Note Limit tables are saved along with the trace data when data is saved to disk Limit tables are not stored in non volatile memory and are not retained when the power is turned off Always save data to disk to preserve the limit tables 4 41 ANALYZE MENU Se Table Index 12 5 kHz Y 13 21 dbV LogMag Spec 0 Table Index X Values 100 k 0 kHz 50 kHz 100 kHz Y Values Top 20 dbV 20 dB div Wndo BMH 8 File Live X begin X end Limit Type Lower More c Return A sample limit table display is shown above The table entries are n table index or line number type of limit upper or lower or Xbegin Xend and Y1 and Y2 For the purposes of testing the limit segments are generated with the assumption that frequency bin O extends from the start frequency to the start frequency plus the linewidth and so on A segment whose Xbegin value is between bin frequencies would test the lower frequency bin s data value against Y1 The rest of the segment is calculated on this basis If more resolution is required then a narrower span is required
216. ld Up to 200 sidebands may be entered though only those which are in the frequency span will enter into the sideband calculations and be identified on the graph If O sidebands are entered the sideband level readout will be zero This key returns to the main Analyze menu 4 34 en ANALYZE MENU Band Band Start 9 0000 kHz Band Center 10 0000 kHz Band Width 2000 0000 Hz Band Start Band Center The Band analysis submenu turns on real time Band analysis and sets the band location A band is a range of frequencies defined by the band start center and width ANALYZE Band Start Band Width The frequency band is identified by a horizontal bar at the bottom of the graph The bar covers the region of the band This key activates the band start entry field If no real time analysis was on when the band submenu was entered then this field is automatically filled with the marker frequency minus half of the band width the band center is set to the marker frequency When this field is activated knob adjustments and numeric entry are permitted Note that knob adjustments are done with the resolution of the current frequency span For increased precision enter the frequency numerically This key activates the band center frequency entry field If no real time analysis was on when the band submenu was entered then this field is automatically filled with the marker frequency The Marker Entry
217. limit tables are stored in this file as well Data files may be recalled into either traceO or trace1 2 ASCII Data File This file saves the data in the active trace in ASCII format These files may not be recaled to the display This format is convenient when transferring data to a PC application 3 Settings File This files stores the analyzer settings Recalling this file will change the analyzer setup to that stored in the file The disk drive uses double sided high density DS HD 3 5 disks The disk capacity is 1 44M The SR770 uses the DOS format A disk which was formatted on a PC or PS2 may also be used Files written by the SR770 may be copied or read on a DOS computer Data files can store data in either binary or ascii format Binary format uses less disk space Ascii format allows trace data to be read by other programs using a PC There are two types of front panel keys which will be referenced in this section Hardkeys are those keys with labels printed on them Their function is determined by the label and does not change Hardkeys are referenced by brackets like this HARDKEY The softkeys are the six gray keys along the right edge of the screen Their function is labelled by a menu box displayed on the screen next to the key Softkey functions change depending upon the situation Softkeys will be referenced as the Soft Key or simply the Soft Key The Measurement This measurement is designed to famili
218. limits 25 ppm from 20 C to 40 C Span 400 Blackman Harris Hanning Flattop and Uniform 100 kHz 1 Single ended or true differential 1 MQ 15 pf AC or DC 90 dB at 1 kHz Input Range lt 6 dBV 80 dB at 1 kHz Input Range 14 dBV 50 dB at 1 kHz Input Range 2 14 dBV 5 nVrms NHz at 1 kHz typical 10 nVrms NHz max 166 dBVrms VHz typ 160 dBVrms VHz 60 dBV 1 0 mVpk to 34 dBV 50 Vpk in 2 dB steps 90 typical No greater than 80 dB from DC to 100 kHz Input Range 0 dBV Input range 2 50 dBV No greater than 85 dB below full scale below 200 Hz No greater than 90 dB below full scale to 100 kHz 16 bit A D at 256 kHz 0 3 dB 0 02 of full scale excluding windowing effects RMS Vector and Peak Hold Linear and exponential averaging up to 64k scans Continuous internal external or external TTL Level Adjustable to 100 of input scale Positive or Negative slope Minimum Trigger Amplitude 10 of input range Level x5V in 40 mV steps Positive or Negative slope Impedance 10 kQ Minimum Trigger Amplitude 100 mV Requires TTL level to trigger low lt 7V high gt 2V Measurement record is delayed by 1 to 65 000 samples 1 512 to 127 time records after the trigger Delay resolution is 1 sample 1 512 of a record Measurement record starts up to 51 953 ms prior to the trigger Delay resolution is 3 9062 us 2 5 770 FFT SPECTRUM ANALYZER DISPLAY
219. ly shows the first 400 points of the record The center is always at the 256th sample which is not at the center of the display To repeat the time record is not a snapshot of the input signal It is the output of the digital filter and the input to the FFT processor ANALYZER BASICS MEASUREMENT BASICS Now that we know that the input to the FFT processor is a complex time record it should be no surprise to find out that the resulting FFT spectrum is also a complex quantity This is because each frequency component has a phase relative to the start of the time record If there is no triggering then the phase is random and we generally look at the magnitude of the spectrum If we use a synchronous trigger then each frequency component has a well defined phase Spectrum The spectrum is the basic measurement of an FFT analyzer It is simply the complex FFT Normally the magnitude of the spectrum is displayed The magnitude is the square root of the FFT times its complex conjugate Square root of the sum of the real part squared and the imaginary part squared The magnitude is a real quantity and represents the total signal amplitude in each frequency bin independent of phase If there is phase information in the spectrum i e the time record is triggered in phase with some component of the signal then the real or imaginary part or the phase may be displayed Remember the phase is simply the arctangent of the rat
220. mand sets or queries the printer type The printer type may be EPSON 0 or HP i 1 5 19 REMOTE PROGRAMMING STORE AND RECALL FILE COMMANDS When using file commands the status byte should be queried after the command is sent to check if the command generated an error Common sources of errors are file not on disk no space on disk and no disk in drive For example the command line SVTR ERRS If will save the data to disk and return the Error Status Byte when finished The Disk Error bit may be checked to make sure that the Save Trace command terminated without error FNAM s SVTR SVTA SVST RCTR RCST The FNAM command sets or queries the active file name All file operations use the name specified by the FNAM command Be sure to use the FNAM s command before any file operation commands For example FNAM MYDATA DAT will set the active file name to MYDATA DAT DOS file name conventions must be followed i e file names are 8 characters or less with an optional extension of up to 3 characters Subdirectories are not supported All file access is to the root directory The SVTR command saves the active trace data display and measurement settings and scaling parameters to the file specified by the FNAM command The associated data and limit tables are also saved The SVTR command saves the data in binary form so that it may be recalled to the display The SVTA command saves the active trace data in
221. mes highlighted The DIDT command deletes the table index highlighted line The DLTB command deletes the entire table 5 13 REMOTE PROGRAMMING LIMIT TABLE COMMANDS The Limit Table commands listed below require that the limit table display be active The commands affect the displayed table and thus the active trace only LIMT TSTS 7 i PASF LTBL 2 i j f1 f2 y1 y2 LINX 2 i LINS LIDT LLTB LARM 7 i The LIMT command activates the limit table for the active trace The screen display changes to the limit table display To turn off the limit table set the display back to single trace mode The TSTS command sets or queries the limit testing on off condition The parameter i selects limit testing Off 0 0 or On i 1 This allows the limit table to be displayed without testing taking place The PASF command queries the result of the latest limit test If the test passed 0 is returned If the test failed 1 is returned The LTBL command sets or queries the limit table The parameter j selects Upper j 0 or Lower j 1 limit The parameters f1 and f2 are Xbegin and Xend f1 and f2 are real numbers of Hz The parameters y1 and y2 are Y1 and Y2 and real unitless numbers The LTBL command queries the entire table The data is returned in the form jf1 2 y1 y2 j f1 f2 y 1 y2 j f1 f2 y 1 y2 If where j f1 f2 y1 y2 are the entries in a single line Line 0 is sent first The LTBL i
222. mmand The earliest command received was IDN and the earliest response was Stanford Research Systems SR770 s n00001 ver007 If Unrecognized characters are ignored and not displayed The terminator character on the output queue is always shown as a When the output is directed to the RS232 interface a carriage return cr is actually sent in place of the If Press any key except PRINT to restore the screen to the graph mode 12 5 kHz Y 13 21 dbV Mele 1 0 1 0100 Output To Receive Queue RS 232 GPIB IDN r STRF F Setup RS232 Setup Transmit Queue GPIB tord Research Systems SR770 s n00001 014 1000 View Queue Stan 0 kHz 50 kHz 100 kHz Top 20 dbV 20 dB div Wado BMH File Live RUN aaa du The Return key will return to the main Setup menu 4 61 EN SYSTEM MENU 4 62 en SYSTEM MENU EHI Setup Sound Key Click on Alarms ot Alarm Length Heturn Key Click Alarms Alarm Length Return The Setup Sound key activates the sound submenu Key click and alarms are enabled and disabled in this menu SYSTEM Key Click On Off Alarms On Off Alarm Length This key turns the key click on and off This key enables and disables the audible alarms Alarms will sound whenever a front panel programming error or interface error occurs Alarms are also used to draw the user s attention to a
223. mmand queries the result of the last real time calculation for trace g The parameter i selects either the upper i 0 or lower i 1 result as displayed on the graph For harmonic analysis CALC g 0 returns the harmonic level and CALC g 1 returns the THD When band analysis is on must be 0 The values returned are exactly as displayed on the graph If the calculation is UnderRange or OverRange the value 1 23E 034 is returned The commands which duplicate the softkeys in the Harmonic Sideband and Band analysis menus are available even if the analysis is not on The analysis parameters may be programmed before analysis is turned on This is not true for the Data and Limit table commands Those commands have no effect if the appropriate table is not active FUND g f NHRM 2 g 1 NHLT NHRT SBCA g f SBSE g f NSBS 1 BSTR g 07 The FUND command sets or queries the harmonic fundamental frequency for trace g The parameter f is a real number of Hz The value of f can be programmed with more resolution than the span linewidth The NHRM command sets or queries the number of harmonics for trace g to i harmonics The parameter i can range from 0 to 400 The NHLT command moves the marker to the next harmonic to the left of the current marker position if it is on the graph If it is beyond the edge of the graph the span center frequency is set to the frequency of the next harmonic or as close as
224. mmunication parameters in this submenu should not be altered while the computer interface is active Output To SYS RS 232 GPIB RS232 Setup Output To RS232 GPIB GPIB Setup RS232 Setup GPIB Baud Rate GPIB Address View Queue i Word Length Overide Remote Parity Return View Queues Output to RS232 GPIB The SR770 only outputs data to one interface at a time Commands may be received over both interfaces but responses are directed only to the interface selected by this key Make sure that the Output interface is set correctly before attempting to program the SR770 from a computer 4 59 SYSTEM MENU Setup RS232 Baud Rate Word Length bits sss P arity Even Odd Setup GPIB GPIB Address Overide Remote No Yos The Setup RS232 key activates the RS232 parameters sub menu Baud rate word length and parity may be configured in this sub menu Baud Rate Word Length Parity Return The Baud Rate key allows the knob to adjust the RS232 baud rate The baud rate can be set to any standard value from 300 to 19200 baud This key toggles the character length The RS232 character length can be 7 or 8 bits 8 bits is standard This key toggles the parity The RS232 parity can be Even Odd or None The Return key will return to the Setup Communications menu The Setup GPIB key activates the GPIB parameters sub menu GPIB instrument address and Rem
225. modate the new span Changing the span will change the Linewidth Span 400 and Acquisition Time 400 Span The Linewidth key selects the linewidth as the active entry field The linewidth is defined as the span divided by 400 The linewidth ranges from 477 mHz to 250 Hz in factors of 2 A numerically entered linewidth is rounded up to the next largest allowable linewidth Changing the linewidth will change the Span Linewidth 400 and Acquisition Time 1 Linewidth If the new span is incompatible with the O to 100 kHz frequency range because the start or center frequency is close to the limits of the range then the start or center frequency will be adjusted to accommodate the new span The Acquisition Time key selects the acquisition time as the active entry field The acquisition time is defined as the reciprocal of the linewidth The 4 1 FREQUENCY MENU M Full Span Start Frequency Center Frequency acquisition time ranges from 2097 1 s to 4 00 ms in factors of 2 A numerically entered acquisition time is rounded down to the next fastest allowable acquisition time Changing the acquisition time will change the Span 400 Acquisition Time and Linewidth 1 Acquisition Time If the new span is incompatible with the O to 100 kHz frequency range because the start or center frequency is close to the limits of the range then the start or center frequency will be adjusted to accommodate the new span Pressing this key imme
226. monic gt Press lt Harmonics gt Press 1 1 lt Enter gt Now let s measure some harmonics using the reference marker Press lt Return gt Press lt None gt 1 4 With this narrow span the harmonics should be easily visible Let s have the analyzer measure the distortion for us First return to full span by displaying the frequency menu and choosing full span Return the graph to a scale where the fundamental is screen This highlights the Start Frequency menu box It also fixes the start frequency when the span is adjusted Reduce the span to resolve the first few harmonics of the signal Display the Analysis menu Choose Harmonic analysis It should still be on from before The fundamental frequency should still be accurately set Highlight the number of harmonics menu box Enter 11 for the number of harmonics Notice that harmonic markers little triangles appear on top of all of the harmonic peaks These indicate which data points are used in the harmonic calculations The harmonic calculations are displayed in the upper left corner of the graph The top reading is the harmonic level absolute units and the lower reading is the distortion harmonic level divided by the fundamental level Return the menu display to the main Analysis menu Choose No analysis This turns off the harmonic indicators and calculations een GETTING STARTED EN Press MARKER MAX MIN Press MARKER R
227. mpling rate of the real record Thus at full span the real points would occur at 256 kHz and the complex points at 128 kHz You can think of the complex record as two separate records one real and one imaginary each with 64 kHz of bandwidth 1 2 of the sample rate One covers 0 to 64 kHz and the other covers 64 kHz to O for a total bandwidth of 128 kHz the same bandwidth as the real record What a negative frequency means is beyond this discussion but suffice to say it works the same The time record display What do you see when you display the time record Clearly the time record is not as simple as the raw digitized data points you would see if this were a digital oscilloscope The analyzer stores the 512 point complex time record described above Because the display is designed for 400 point spectra only the first 400 points of the time record are displayed You can use the trigger delay to translate the time record to see the part not normally displayed The time record for every span has been digitally filtered and heterodyned into a complex record You can display the magnitude real or imaginary part as well as the phase Normally the easiest display to 2 3 understand is Linear Magnitude Remember that magnitudes are always positive The negative parts of the waveform will be folded around zero so that they appear positive Because of the filtering and heterodyning the time waveforn may not closely resemble the
228. mplitude within 1 3 octave bands The analyzer computes a normal FFT then calculates the rms sum of the frequency components within each band When Octave Analysis is on only the Log Magnitude may be displayed Also the display is always logarithmic on the X axis displaying evenly spaced octaves The left and right most bands are labelled on the graph by center frequency and band number The marker reads the center frequencies of the bands rounded to the nearest even frequency The actual band frequencies are exact according to the ANSI standard Note When octave analysis is on for either trace the FREQ menu will display the band menu for both traces This is because both traces must have the same span Thus if one trace is measuring octave analysis the other trace s span is determined by the bands displayed in the octave analysis Furthermore in order to perform 30 band analysis accurately the SR770 must combine spectra taken with two different overlapping spans This is because the frequency range of 30 bands requires more than 400 linearly spaced frequency points When 30 band analysis is chosen the analyzer alternates between two different spans If one trace is displaying 30 band octaves then the other trace will show spectra taken with alternating frequency spans and is not very useful In general when using octave analysis only the trace showing octaves is meaningful Only one trace may be measuring octave analysis at a time
229. n 6 18 eee PERFORMANCE TESTS 10 Noise and Spurious Signals This test measures the analyzer noise floor and checks for spurious signals Setup Connect a 500 feedthrough termination to the A input This grounds the input so the analyzer s own noise is measured Procedure 1 PRESET Turn the analyzer off wait a few seconds then back on with the key pressed 2 Press the keys in the following sequence FREQ Span 5 0 kHz lt Start Freq gt 1 lt kHz gt INPUT lt Input Range gt 5 0 lt dBV gt MEAS lt Measure Menu gt lt PSD gt lt Return gt lt Units Menu gt lt dBVrms gt SCALE lt Top Ref gt 4 0 lt dBV VHz gt AVERAGE lt Number of Averages gt 2 0 lt Enter gt lt Averaging gt Select On MARKER MAX MIN 3 Record the marker Y reading 4 Press FREQ lt Start Freq gt 5 0 lt kHz gt START MARKER MAX MIN 5 Record the marker Y reading 6 19 PERFORMANCE TESTS 6 Press MEAS lt Measure Menu gt lt Spectrum gt lt Return gt lt Units Menu gt lt dBV gt 7 For each of the spans listed below perform steps 7a and 7b Center Frequency Span 200 Hz 390 Hz 500 Hz 390 Hz 1 kHz 1 56 kHz 5 kHz 1 56 kHz 10 kHz 1 56 kHz 25 kHz 1 56 kHz 50 kHz 1 56 kHz 75 kHz 1 56 kHz 99 kHz 1 56 kHz a Press FREQ lt Span gt Enter the span from the table lt Center Freq gt Enter the center frequency from
230. n The MRKY command queries the trace g marker Y position The value returned is the same as the marker readout on the screen The MRPK command performs the same function as pressing the MARKER MAX MIN key The marker region will be centered around the maximum or minimum data value on the screen depending upon the marker seeks mode Only the marker on the active graph is affected The MRCN command performs the same function as pressing the MARKER CENTER key The center frequency of the span is set to the marker frequency on the active graph The span is decreased if necessary to accomplish this The MRRF command sets the marker offset for the active graph equal to the marker position both X and Y and turns the marker offset on if it was off Similar to the MARKER REF key The MROF command sets or queries the marker offset Off On state The parameter i selects Off 150 or On i21 5 7 REMOTE PROGRAMMING MROX x MROY x PKLF PKRT MSGS s The MROX command sets or queries the marker X offset The offset is a unitless real number usually interpreted as a frequency The MROY command sets or queries the marker Y offset The offset is a unitless real number The PKLF command moves the marker to the next peak to the left The PKRT command moves the marker to the next peak to the right The MSGS s command displays string s in a message window on the screen An alarm is also sounded The str
231. n General Installation Necessary Equipment If A Test Fails Performance Tests Self Tests DC Offset Common Mode Rejection Amplitude Accuracy and Flatness Amplitude Linearity Anti Alias Filter Attenuation Frequency Accuracy Phase Accuracy Harmonic Distortion Noise and Spurious Signals Sine Source Performance Test Record CIRCUIT DESCRIPTION Circuit Boards Video Driver and CRT CPU Board 5 16 5 18 5 19 5 20 5 21 5 23 5 24 5 25 5 25 5 25 5 26 5 26 5 27 5 27 PPD 61 gt 2 OD N e gt gt 6 23 NN Microprocessor System Keypad Interface Keyboard Interface Spin Knob Speaker Clock Calendar Printer Interface Video Graphics Interface Disk Controller GPIB Interface RS232 Interface Expansion Connector Power Supply Board Unregulated Power Supplies Power Supply Regulators DSP Logic Board Overview DSP Processors Trigger Timing Generator Interface Source Analog Input Board Overview Input Amplifier Gain Stages and Attenuators Anti Alias Filter A D Converter Interface Power Parts Lists CPU Board Power Supply Board DSP Logic Board Analog Input Board Chassis Assembly Miscellaneous Schematic Diagrams CPU Board Power Supply Board DSP Logic Board Analog Input Board EN TABLE OF CONTENTS 72 7 2 7 2 7 3 7 4 7 4 7 4 7 4 7 4 7 4 7 4 7 4 770 FFT SPECTRUM
232. n as fast as the trigger delay and actual time record length permit With Manual arming no time records are taken until the trigger is armed either from the front panel using the Arm Trigger softkey or upon receipt of an arming command from a computer interface Once the trigger is armed the next trigger event will trigger a time record The trigger is not automatically re armed but waits for an arming command or key Note If the trigger mode is continuous the arming mode has no effect If the unit is in a triggered mode and arming is set to manual then the Arm Wait indicator will light if the unit is not armed after a few seconds This is a reminder that the unit is waiting Once the unit is armed the Armed indicator will light The Trg Wait and Trigger indicators will not turn on unless the unit is armed Arm This key manually arms the trigger This function only appears if the arming mode is manual 4 25 INPUT Return This key returns to the Trigger configuration submenu 4 26 Scale Top Ref Bottom Ref 140 Top Reference Bottom Reference Y Div SCALE MENU The Scale menu is used to change the graph X and Y scaling parameters for the active trace Bottom Ref Auto Scale Expand X This key activates the Top Reference entry field The top reference is the Y value of the top of the active trace graph The top reference is expressed in the same u
233. n auto offset calibration Auto Offset is always set to On when the analyzer is turned on Setting Auto Offset to Off defeats the periodic offset calibration Turning Auto Offset On immediately performs an offset calibration and then every few minutes for the first half hour and then less often after that The offset calibration takes about a 10 seconds After offset calibration the DC frequency bin of any baseband measurement will be minimized To calibrate the offsets the inputs are internally grounded and the amplifier offsets are measured and stored When making very narrow span measurements the analyzer will need to re settle after a calibration In these cases it may be best to leave the Auto Offset Off and perform the calibration only when necessary 4 21 INPUT Trigger Trigger Cont Int Src Ext TT Trigger Level 2 5V Trigger Slope Trigger Delay 0 1 5625 mS Arming Menu Return Trigger The Trigger submenu is used to set the trigger mode level and delay The Arming submenu selects the arming mode The Trigger key selects the trigger type Continuous is the same as free run The analyzer takes time records continuously Internal trigger means that time records are triggered by the input signal itself This is similar to an oscilloscope on internal trigger On External or TTL the time records are triggered by the external trigger input on the front panel T
234. n the span is narrowed the bins move much closer together and it becomes very hard to place a signal exactly on a frequency bin ANALYZER BASICS WINDOWING What is windowing Let s go back to the time record What happens if a signal is not exactly periodic within the time record We said that its amplitude is divided into multiple adjacent frequency bins This is true but it s actually a bit worse than that If the time record does not start and stop with the same data value the signal can actually smear across the entire spectrum This smearing will also change wildly between records because the amount of mismatch between the starting value and ending value changes with each record Windows are functions defined across the time record which are periodic in the time record They start and stop at zero and are smooth functions in between When the time record is windowed its points are multiplied by the window function time bin by time bin and the resulting time record is by definition periodic It may not be identical from record to record but it will be periodic zero at each end In the frequency domain In the frequency domain a window acts like a filter The amplitude of each frequency bin is determined by centering this filter on each bin and measuring how much of the signal falls within the filter If the filter is narrow then only frequencies near the bin will contribute to the bin A narrow filter is called a
235. nactive trace is replaced with the data table window The data table reports the Y values for user entered X locations For example the entries could be a set of harmonic frequencies which need to be monitored To generate a report of the measurement the active trace s data table may be printed out using the Plot menu Each trace has its own data table though only the table associated with the active trace is active and displayed at any time To remove the data table display change the Format in the Display menu back to Single If no data table is entered or the data table has been deleted and harmonic or sideband analysis is turned on then this key not only activates the data table display but also enters the harmonic or sideband locations into the table This key turns on the limit table for the active trace and displays the limit table submenu which is described in the following pages The screen format will Switch to the dual trace mode and the inactive trace is replaced with the limit table window The limit table lists the coordinates of the line segments which define the trace limits When trace data exceeds these limit segments then the Fail message appears and an audio alarm sounds To generate a listing of the active trace s limit table use the Print Limits function in the Plot menu Each trace has its own limit table though only the table associated with the active trace is active and displayed at any time To remove the limit table
236. nd connections of any external equipment and if possible verify its operation using a DVM scope or some other piece of test equipment After checking the setup repeat the test from the beginning to make sure that the test was performed correctly If the test continues to fail contact Stanford Research Systems for further instructions Make sure that you have the unit s serial number and firmware revision code handy Have the test record on hand as well PERFORMANCE TESTS 1 Self Tests The self tests check the analyzer hardware These are functional tests and do not relate to the specifications These tests should be run before any of the performance tests Note that the Test menu offers more tests than are required here Only those tests which require no additional equipment are discussed in this section The computer interface and disk drive tests are not required but should be periodically checked See the System Setup menu for more information about those tests Setup No external setup is required for this test Procedure 1 PRESET Turn on the analyzer with the lt key pressed At power up the RAM ROM DSP and A D tests should all be OK 2 Press the keys in the following sequence SYSTEM SETUP lt More gt lt Test Hardware gt lt Keypad Test gt Press all of the front panel keys until all of the boxes on the screen are filled in Rotate knob to exit this screen lt Knob Test gt lt Spee
237. ndependent of whether a serial poll has occurred to clear the service request Using SERIAL POLL Except for SRQ a bit in the Serial Poll status byte is NOT cleared by polling the status byte When reading the status byte using a serial poll the SRQ bit signals that the SR770 is requesting service The SRQ bit will be set 1 the first time the SR770 is polled following a service request The serial poll automatically clears the service request Subsequent serial polls will return SRQ cleared 0 until another service request occurs Polling the status byte and reading it with STB can return different values for SRQ When polled SRQ indicates a service request has occurred When read with STB SRQ indicates that an enabled status bit is set 5 28 eee REMOTE PROGRAMMING SERVICE REQUESTS SRQ A GPIB service request SRQ will be generated whenever a bit in both the Serial Poll Status byte AND Serial Poll Enable register is set Use SRE to set bits in the Serial Poll Enable register A service request is only generated when an enabled Serial Poll Status bit becomes set changes from 0 to 1 An enabled status bit which becomes set and remains set will generate a single SRQ If another service request from the same status bit is desired the requesting status bit must first be cleared In the case of the ERR FFT and ESB bits this means clearing the enabled bits in the ERR FFT and ESB status bytes by reading them Multiple enabled bit
238. nits as the display and marker as set in the Measure menu This key activates the Bottom Reference entry field The bottom reference is the Y value of the bottom of the active trace graph The bottom reference is expressed in the same units as the display and marker as set in the Measure menu This key activates the Y Division entry field This value is the vertical scale of the active trace graph If the display is linear then the vertical scale is expressed in the displayed units If the display is logarithmic then the vertical scale is always dB division Remember that the reference values and marker readouts in this case are still shown in the previously selected units Using the knob adjusts the vertical scale in a 1 2 5 10 sequence Knob adjustments leave the marker at the center of the graph The top and bottom reference will be adjusted to make this happen This gives the effect of vertical zooming By using the numeric entry keys almost any scale may be entered In this case the top reference remains fixed while the bottom reference changes 4 27 SCALE MENU M Auto Scale Expand X X axis Pressing this key will automatically set the vertical scale and top and bottom reference of the active trace to display the entire range of the trace Horizontal scaling is not affected AutoScale only operates on the data which is displayed on the graph If the graph is expanded data corresponding to frequency or time bins which
239. not connected directly to the analyzer chassis ground In Float mode the shields are connected by 1 to the chassis ground In Ground mode the shields are connected by 50 to the chassis ground In this mode do not exceed 3V on the shields The impedance between the center conductor of each input and the shield is always 1 Note When the input source configuration is set to A B the grounding is automatically set to Ground This is because in the A B case the shields are exactly that shields and do not carry signal This key toggles the input coupling between AC and DC The 3 dB bandwidth of the AC setting is 0 16 Hz 4 20 en INPUT MENU Input Range Trigger Menu Auto Offset This key activates the Input Range entry field The input range can only be adjusted using the knob The displayed value is the full scale signal input just before overload The input range limits are 60 dBV to 34 dBV in 2 dBV steps If the input ranging mode is Manual as toggled by the AUTO RANGE key and displayed by the Man Rng indicator then this field sets the input range If the input ranging mode is AutoRng then this field displays the current range Adjusting the input range automatically toggles back to manual ranging mode This key displays the Trigger configuration menu as described on the following page This function enables Auto Offset calibration When Auto Offset is On the analyzer will periodically perform a
240. not required The chirp waveform consists of 400 sine waves each one perfectly periodic in the time record The chirp waveform requires a uniform window to result in a flat spectrum This is because the individual frequency components do not have a constant amplitude over the time record Windowing will attenuate certain portions of the spectrum Source Trigger The Sine Two Tone and Chirp sources can be triggered to measure phase response and or vector average The Source Trigger mode simply sets the overlap to 0 so each time record follows immediately after the previous one with no delay For the chirp source each time record will be identical so the phase of each component will be stable The absolute phase of the record is arbitrary since the source does not turn on and off synchronously with the input time record Turning on and off the source changing the span performing Auto Offset can all change the absolute phase of the time record The Auto Phase function can be used to set all the phase of each component to zero Subsequent phase measurements will be relative to zero For sine and two tone the source frequencies must be set to a multiple of the linewidth in order for a stable time records to be acquired Random frequencies are not exactly periodic over a time record and do not result in a stable phase Once again the absolute phase is arbitrary since the source does not turn on synchronously with the input time rec
241. nt using a 2 channel analyzer except that the output ripple is measured at the factory and is not adjustable by the user Remember the Source Cal mode compensates for variations in the output spectrum by adjusting the input calibrations The actual signal at the Source Output is not affected Source Cal has NO effect unless the source is Chirp or Noise Source Cal can only be selected in the Configure Noise or Chirp submenu Do not select Source Cal On and use an external signal source The input calibrations are modified and will result in measurement errors unless the SR770 internal source is used as the test signal This key returns the main source selection menu 4 55 SOURCE M Configure Chirp Chirp Level 1000 mV Auto Phase Source Cal ea On Return Chirp Level The Configure Noise submenu allows the chirp level to be set and Auto Phase to be performed SOURCE Configure Source Chirp Level Auto Phase Source Cal The Chirp source provides an equal amplitude sine wave at each bin of the measurement span The phases of each sine wave are arranged so that they do not add in phase and the output does not peak The chirp is EXACTLY periodic over a time record and requires no window Because of cancellation the amplitude of each sine wave is NOT constant over the time record Windowing the time record actually removes necessary spectral information USE THE UNIFORM WINDOW WITH
242. nter Freq gt Press 5 0 kHz Press START Go to the Frequency menu Highlight the Center Frequency Enter 50 kHz Take another spectra The final PSD level should be the same as the reading taken at full span at 50 kHz The reading is not exactly the same of course That would take an infinite number of averages Remember the noise output covers the spectrum from 0 to 100 kHz regardless of the measurement span In this case the measurement span extends from 37 5 62 5 kHz while the noise output is still full Span The response of many systems is characterized using noise as the input White noise equal noise in equal bandwidth is generally used in electronic measurements Pink noise equal noise per frequency octave is preferred in acoustic systems such as the natural response of an enclosure or speaker White noise generates a flat Power Spectral Density curve Pink noise generates a flat response in Octave Analysis 1 41 ENN GETTING STARTED M USING THE CHIRP SOURCE 1 the analyzer on while holding down the lt backspace key Wait until the power on tests are completed 2 Connect the SR770 Source output to the A input Press SOURCE Press lt Chirp gt Press AUTO RANGE 3 Press MEAS Press lt Window Menu gt Press lt Uniform gt 4 Press INPUT Press lt Trigger Menu gt Press lt Trigger gt 4 times to select Source When the power is turned on with the backspa
243. nuation test Enter the results of this test in the test record at the end of this section 6 13 PERFORMANCE TESTS 7 Frequency Accuracy This test measures the frequency accuracy of the analyzer This tests the accuracy of the fundamental crystal timebase inside the unit Setup We will use the frequency synthesizer to provide the signal Connect the output of the frequency synthesizer to the A input of the analyzer Be sure to use the appropriate terminations where required Procedure 1 PRESET Turn the analyzer off and on with the lt key pressed 2 Set the frequency synthesizer to a frequency of 10 kHz and an amplitude of 400 mVrms 3 Press the keys in the following sequence FREQ lt Span gt 1 2 Hz Center Freq gt 1 0 kHz INPUT lt Input Range gt 2 lt 9 gt AUTO SCALE MARKER MAX MIN 4 Wait for the spectrum to settle then record the marker frequency reading 3 This completes the frequency accuracy test Enter the results of this test in the test record at the end of this section 6 14 eee PERFORMANCE TESTS 8 Phase Accuracy This test measures the phase accuracy of the analyzer This test measures the phase of a signal relative to the trigger Setup We will use the frequency synthesizer to provide the signal Connect the output of the frequency synthesizer to the A input of the analyzer Be sure to use the appropriate terminations where required
244. o 500 averages The SR770 on the other hand has a real time bandwidth of 100 kHz At a 100 kHz span the analyzer is capable of processing 250 spectra per second In fact this is so fast that the display can not be updated for each new spectra The display only updates about 6 times a second However when averaging is on all of the computed spectra will contribute to the average The time it takes to complete 500 averages is only a few seconds Instead of a few minutes Overlap What about narrow spans where the time record is long compared to the processing time The analyzer computes one FFT per time record and 2 8 can wait until the next time record is complete before computing the next FFT The update rate would be no faster than one spectra per time record With narrow spans this could be quite slow And what is the processor doing while it waits Nothing With overlap processing the analyzer does not wait for the next complete time record before computing the next FFT Instead it uses data from the previous time record as well as data from the current time record to compute the next FFT This speeds up the processing rate Remember most window functions are zero at the start and end of the time record Thus the points at the ends of the time record do not contribute much to the FFT With overlap these points are re used and appear as middle points in other time records This is why overlap effectively speeds up av
245. o displayed on the screen when the unit is powered on The serial number can also be displayed by pressing SYSTEM SETUP lt More gt lt Test Hardware gt lt More gt lt Screen Test gt Firmware Revision The firmware revision code is displayed on the screen when the unit is powered on The revision code is displayed along with the serial number in the System Setup menu as described above General Installation POWER Make sure that the power entry module on the rear panel is set for the AC line voltage in your area and that the correct fuse is installed The selected AC voltage may be seen through the window on the power entry module Verify that the line cord is plugged all the way into the power entry module and that the power button on the front panel is pressed in PERFORMANCE TESTS SCREEN BRIGHTNESS If the screen is too dark or too bright adjust the brightness using the knob at the upper left of the screen Do not set the brightness higher than necessary DISPLAY POSITION Use the Setup Screen function in the SYSTEM SETUP menu to position the display in the center of the screen FAN The fan in the SR770 is temperature controlled When the unit is cold the fan is at half speed When the internal temperature reaches about 30 C the fan speed increases Do not block the vents in the chassis or the unit may not operate properly 6 2 Necessary Equipment The following equipment is necessa
246. o the active graph Recall the Settings from the file specified by FNAM description Set Query the Operation to x log Y 0 5 Start the calculation Set Query the Argument type to Constant 0 w 1 or Other Graph 2 Set Query the Constant Argument to x Set the Constant Argument to the Y value of the marker page description 5 20 Start data acquisition Same as START key 5 20 Pause or Continue data acquisition Same as PAUSE CONT key 5 20 Print the screen Same as PRINT key 5 20 Set Query the Active Trace to traceO 0 or trace1 1 Similar to ACTIVE TRACE key 5 20 Set Query the Auto Range mode to Manual 0 or Auto 1 Similar to AUTO RANGE key 5 20 AutoScale the graph Same as the AUTO SCALE key page description 5 21 Query the Y value of bin 0 x i lt 399 5 21 Query the X value of bin 0 x i lt 399 5 21 Binary dump the entire trace g 5 22 Set Query the auto binary dump mode for trace g page description 5 23 Reset the unit to its default configurations 770 FFT SPECTRUM ANALYZER IDN 5 23 Read the SR770 device identification string LOCL i 5 23 Set Query the Local Remote state to LOCAL 0 REMOTE 1 or LOCAL LOCKOUT 2 OVRM i 5 23 Set Query the GPIB Overide Remote state to Off 0 or On 1 STATUS page description CLS 5 24 Clear all status bytes ESE i 04 5 24 Set Query the Standard Status Byte Enable R
247. of the screen Their function is labelled by a menu box displayed on the screen next to the key Softkey functions change depending upon the situation Softkeys will be referenced as the lt Soft Key gt or simply the Soft Key 1 6 The Measurement This measurement is designed to investigate the noise of an audio amplifier You will need an audio frequency amplifier such as the SRS SR560 We will use the SR770 s source to provide the test signal Specifically you will measure the output signal noise ratio of the amplifier and its input noise level eee GETTING STARTED EN MEASURING AMPLIFIER NOISE 1 Turn the analyzer on while holding down the lt backspace key Wait until the power on tests are completed 2 Turn on the amplifier and set its gain to at least 20 dB Connect the amplifier output to the A input of the analyzer Press SOURCE Press lt Sine gt Press lt Configure Source gt Press lt Level gt Press 1 0 0 lt mV gt Connect the SR770 Source output to the amplifier input 3 Press AUTO RANGE Press FREQ Press SPAN DOWN until the span is 6 25 kHz Press AUTO SCALE 4 Press MARKER MAX MIN Press MARKER REF 1 7 When the power is turned on with the backspace key depressed the analyzer returns to its default settings See the Default Settings list in the Menu section for a complete listing of the settings The input impedance of the analyzer is 1 The ampl
248. on power up If 150 the is cleared and the status enable registers maintain their values at power down This allows a service request to be generated at power up The ERRE i command sets the error status enable register to the decimal value i 0 255 The ERRE i j command sets bit i 0 7 to j 0 or 1 The ERRE command queries the value 0 255 of the error status enable register The ERRE i command queries the value 0 or 1 of bit i The ERRS command queries the value of the error status byte The value is returned as a decimal number from 0 to 255 The ERRS i command queries the value 0 or 1 of bit i 0 7 Reading the entire byte will clear it while reading bit i will clear just bit i The FFTE command sets the analyzer FFT status enable register to the decimal value i 0 255 The FFTE i j command sets bit i 0 7 to j 0 or 1 The FFTE command queries the value of the FFT status enable register The FFTE i command queries the value 0 or 1 of bit i The FFTS command queries the value of the analyzer FFT status byte The value is returned as a decimal number from 0 to 255 The FFTS i command queries the value 0 or 1 of bit i 0 7 Reading the entire byte will clear it while reading bit i will clear just bit i 5 26 ee REMOTE PROGRAMMING 5 27 REMOTE PROGRAMMING STATUS BYTE DEFINITIONS The SR770 reports on its status by means of four status bytes the serial poll status byte the standard s
249. onths setting of the calendar The value of i is in the range 1 O i 112 The DDAY command sets or queries the days setting of the calendar The value of i is in the range 1 O i 031 The DYRS command sets or queries the years setting of the calendar The value of i is in the range 0 O i 199 The PLTM command sets or queries the plotter mode If i 0 plotting is directed to the RS232 interface if i 1 plotting is to the GPIB interface The PLTB command sets or queries the RS232 plotter baud rate The parameter i ranges from 0 to 4 and selects baud rates of 300 0 1200 1 2400 2 4800 3 and 9600 4 This baud rate should match the baud rate of the plotter in use The PLTA command sets or queries the GPIB plotter address The parameter i ranges from 0 to 30 and should agree with the address of the plotter in use The PLTS command sets or queries the plot speed If 0 fast plot speed is used if i 1 slow plot speed is used The PNTR command sets or queries the trace pen number The pen number is in the range of 1 to 6 The PNGD command sets or queries the grid pen number The pen number is in the range of 1 to 6 5 18 en REMOTE PROGRAMMING PNAP 7 i PNCR i PRNT i The PNAP command sets or queries the alphanumeric pen number The pen number is in the range of 1 to 6 The PNCR command sets or queries the marker pen number The pen number is in the range of 1 to 6 The PRNT com
250. ord Noise Broadband is useful for characterizing circuits mechanical systems or even the audio response of an entire room White noise provides equal amplitude per root Hz from O to 100 kHz regardless of the measurement span White noise is useful in electronic applications Pink noise rolls off at 3 dB oct providing equal amplitude per octave Pink noise is preferred in audio applications Since the signal is noisy and random windows are always required when using the noise source Source triggering is not meaningful since there is no stable phase information in the source een ANALYZERBASICS 2 11 OPERATION EH FRONT PANEL OVERVIEW Brightness Control Soft Keys Spin Knob Power Button Video Display POWER BUTTON The SR770 is turned on by pushing in the POWER button The video display may take a few seconds to warm up and become visible Adjust the brightness until the screen is easily readable The model firmware version and serial number of the unit are displayed when the power is turned on A series of internal tests are performed at this point Each test is described as it is performed and the results are represented graphically as OK or NOT OK The tests are described below RAM This test performs a read write test to the processor RAM In addition the nonvolatile backup memory is tested All instrument settings are stored in nonvolatile memory and are retained when the power is turne
251. ost computer interface should be interrupt driven or have fast data communication routines since the data transmission is limited only by the baud rate If SPEC is used to transfer the entire trace the returned data will be from the latest trace The BVAL g i command queries the X value of bin i of trace g The returned value is either a frequency spectra a time time record or a band center frequency octave analysis The first bin is 0 and the last bin is i 399 i214 or i229 for 15 or 30 band octave analysis The SPEB g command reads the Y values of the entire trace g data record in binary format over the GPIB interface The SPEB g command is not available over the RS232 interface SPEB g returns the entire trace record 2 bytes per bin starting with bin O and continuing to bin 399 bin 14 or bin 29 for 15 or 30 band octave analysis There is no separation between data points No line feed follows the last data point instead EOI is asserted with the last byte Each data point is sent low byte first then high byte The 2 bytes represent the data point in 16 bit 2 s complement format The returned values are interpreted as follows Linear data Data Value 32 768 x full scale Volts 180 deg or radians Log data Data 3 0103 x Value 512 114 3914 dB full scale When using the SPEB g command the host interface must be capable of binary transfer i e accepting line feeds and carriage returns as data rather
252. ote Overide are set in this sub menu GPIB Address Overide Remote Return This key activates the GPIB Address entry field for numeric and knob entry The instrument address can be set from 0 to 30 In general every GPIB interface command will put the SR770 into the REMOTE state with the front panel inactivated To defeat this feature set the Overide Remote to Yes In this mode the front panel is not locked out when the unit is in the REMOTE state If the SR770 is in the REMOTE state the HELP key returns the unit to local front panel control The Return key will return to the Setup Communications menu 4 60 en SYSTEM MENU EHI View Queue Return The last 256 characters received or transmitted by the SR770 may be displayed to help find programming errors The View Queue key will display the interface buffers at the time the key is pressed This screen is updated regularly to display new interface activity The View Queue screen may slow down the communications between the SR770 and a host computer In general the View Queue screen should be displayed only when testing or debugging a host program The most recent data is displayed at the right of the upper line of each queue display For example in the screen below the STRF If string was the most recently received command The f character is a line feed and is the string delimiter The most recently transmitted string is 1000 0 If in response to the STRF co
253. otherwise any disk that you don t mind formatting will do Make sure the write protect tab is off Let s format this disk Display the Store and Recall menu Choose Disk Utilities Make sure that the disk does not contain any information that you want Formatting the disk takes about a minute Go back to the main Store and Recall menu Display the Save Data menu 1 15 GETTING STARTED 10 11 12 13 14 15 16 17 Press File Name Press ALT Press D A T A 1 Enter Press Save Data Press Catalog Press File Name Press ALT Press D A T A 2 Enter Press Save Data Press Return Press START Remove the input signal cable Press Recall Data Press Catalog Press MARKER Press Recall Data Now we need a file name ALT lets you enter the letter characters printed below each key The numbers and backspace function as normal Enter a file name such as DATA1 or any legal DOS file name This saves the active trace data to disk using the file name specified above Display the disk catalog This display lists all of the files on the disk Save the data again using a new file name This way you can have multiple files in the disk catalog Go back to the main Store and Recall menu Resume data acquisition The graph should be live again Now we have a spectrum which is different from the one
254. ource Noise Level This key activates the noise level entry field The output level is expressed in mVpk The level may be entered in either mVpk or dBVpk The knob always adjusts the level in mVpk The resolution is 1 mV for levels greater than 100 mV and 0 1 mV for levels less than 100 mV With white noise the noise level is approximately the peak amplitude of the noise output There will be occasional voltage excursions beyond this level Because of the nature of noise the peak amplitude is not a perfectly defined quantity Pink noise is generated starting with white noise and then filtering it to achieve a 3 dB oct roll off This filtering means that the pink noise voltag amplitude is much less than the white noise The pink noise level is actually the white noise 4 54 en SOURCE MENU Source Cal Return level before filtering The actual pink noise output level is much smaller than the pink noise level displayed in the menu However the menu still provides a relative amplitude control This key turns the Source Cal on and off The source is digitally synthesized and passes through an output reconstruction filter The spectrum of broadband outputs such as noise exhibit the passband ripple of this filter Source Cal adjusts the input calibration to compensate for the output reconstruction filter ripple The spectrum of the white noise output will appear flat when Source Cal is on This is similar to a ratio measureme
255. r 10 as selected by relay K107 When a gain of 10 is 7 7 selected the offset and CMR are adjusted P102 and P101 respectively When a gain of 2 is selected offset and CMR are adjusted via P104 and P103 respectively GAIN STAGES AND ATTENUATORS Collectively the front end amplifier gain stages and attenuators provide attenuation from 12dB to 0 dB and gain from 2dB to 60dB 203 steps This is accomplished through the front end amplifier two gain stages and a resistive ladder attenuator The first gain stage is configurable as either a 14dB or 20dB amplifier The second stage provides only one gain setting of 20dB To achieve the desired gain the front end amplifier and these two gain stages are cascaded together If any particular gain stage is not needed it s input is grounded This maintains a cleaner power supply and reduces the ability of potentially large signals in unused gain stages from interacting with the input signal to cause harmonic distortion U206 forms an analog multiplexer and selects one of the three gain stage outputs or an attenuated front end amplifier output This enables several different overall gains to be realized while utilizing a minimum number of gain stages The input signal is never passed through gain stage unnecessarily This improves the noise and harmonic distortion performance of the overall amplifier Referenced to the input of the front end amplifier gains of 2dB 6dB 2
256. r Electrolytic 25V 20 Rad Capacitor Electrolytic 25V 20 Rad Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U 7 16 eee PARTS LIST REF C 610 C 611 C 612 C 613 C 614 C 615 C 616 C 630 C 631 C 632 C 633 C 634 C 635 C 636 C 637 C 638 C 639 C 640 C 641 C 642 C 643 C 644 C 645 C 646 C 647 C 648 C 649 C 650 C 651 C 652 C 653 C 654 C 656 C 657 C 658 C 659 C 661 C 662 C 663 C 668 C 669 C 670 C 671 C 672 C 673 C 675 D 301 D 302 J 301 J 501 K 301 SRS PART 5 00023 529 5 00127 524 5 00219 529 5 00100 517 5 00219 529 5 00127 524 5 00219 529 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00034 526 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 5 00225 548 3 00004 301 3 00004 301 0 00388 000 0 00388 000 3 00196 335 VALUE 2 20 01U 2 2U 01U 2 2U 01U 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1U AXIAL 1
257. r mode and perform various marker functions The marker functions can be accessed from any menu A complete description of the keys follows in the next section SPIN KNOB The spin knob is used to adjust parameters which have been highlighted using the soft keys Most numeric entry fields may be adjusted using the 3 2 The main area of the display is occupied by the data trace display Data is graphed as signal on the vertical axis and frequency or time bin on the knob In addition functions such as display zooming and scrolling use the knob as well In these cases the knob function is selected by the soft keys The MARKER key which can be pressed at any time will set the knob function to scrolling the marker DISK DRIVE The 3 5 disk drive is used to store data and instrument settings Double sided double density disks should be used The disk capacity is 720k bytes formatted The disk format is DOS compatible Disks written by the SR770 may be read by PC compatible computers equipped with a 3 5 drive and DOS 3 0 or higher Only use double sided double density DS DD disks Do not use high density DS HD disks BNC CONNECTORS TRIGGER The rising or falling edge of the TRIGGER input triggers a time record The input impedance is 10 and the minimum pulse width is 10 ns The trigger level is adjustable from 5V to 5V with either positive or negative slope The minimum pulse amplitude is 100 mV SIGNAL IN
258. r is triggered The phase is relative to the start of the time record The phase is displayed in degrees or radians on a linear scale from 180 6 to 180 6 degrees rads The phase may be unwrapped using the Calculator in the Measure menu The phase is calculated starting with the left most bin If neither the real nor imaginary component of a bin is greater than 0 018 of full scale 75 dB below f s then the phase is not calculated In this case the phase is set to the phase of the most recent bin which exceeded 0 018 of full scale This avoids the messy phase display associated with the noise floor Remember even if a signal is small its phase extends over the full 360 degrees This display method also preserves cumulative phase rotation as a function of frequency The Return key will return to the main MEAS menu 4 8 en MEASURE MENU EN Units Volts Pk Volts RMS vom ev Return joj Volts Pk EU PK Volts RMS EU RMS dBV dBEU dBVRMS dBEURMS Volts EU The Units sub menu allows the user to choose the display units for the active trace MEAS Volts Pk Volts HMS dBV Return a dBVrms Return EU Label EU Volt Return This key chooses units of Volts Peak or Engineering Units Peak for the active trace This key chooses units of Volts RMS or Engineering Units RMS for the active trace This key chooses units of dBVolts Peak or dBEngineering Units Peak
259. ramic 50V 20 Z5U Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Monolythic Ceramic COG 1 Capacitor Monolythic Ceramic COG 1 Capacitor Monolythic Ceramic COG 1 Capacitor Monolythic Ceramic COG 1 Capacitor Monolythic Ceramic COG 1 Capacitor Monolythic Ceramic COG 1 Capacitor Monolythic Ceramic COG 1 Capacitor Ceramic Disc 50V 10 SL Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 50V 20 Rad Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 50V 20 Rad Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Ceramic Disc 50V 10 SL Capacitor Tantalum 50V 20 Rad Capacitor Tantalum 50V 20 Rad Capacitor Tantalum 50V 20 Rad Capacitor Tantalum 50V 20 Rad Capacito
260. re read from the root directory This key toggles the file catalog display screen on and off The use of this key is identical to the Catalog On Off function in the Recall Trace sub menu above The Return key will return to the main Store Recall menu Return also removes the catalog display screen and restores the graph 4 82 ee STORE RECALL MENU Disk Utilities Format Disk I Erase File Return The Disk Utilities submenu contains the Format Disk and Erase File functions These functions should be used with care since disk data will be erased The catalog screen is displayed with this submenu if a formatted disk is in the drive Format Disk Erase File Return Pressing this key will format the disk Formatting a disk involves erasing all information on the disk and rewriting the directory Formatting a disk destroys all data presently on the disk Use caution when choosing this function Disk capacity is 1 44 MB formatted The maximum number of directory entries is 224 This is the DOS limitation on the number of files allowed in the root directory This function will erase the highlighted file To select a file activate the cursor with the MARKER key and use the knob to scroll the file entries Make sure the selected file is the correct file before pressing this key The Return key will return to the main Store Recall menu Return also removes the catalog display screen and restor
261. requency f Hz Set Query the Sideband Separation to f Hz Set Query the Number of Sidebands to 0 lt i lt 200 Set Query the Band Start to frequency f Hz Set Query the Band Center to frequency f Hz Set Query the Band Width to f Hz Turn on Data Table display for the active trace Set Query Data Table line i to frequency f Set Query Data Table index to i Insert a new line in the data table Delete a line from the data table Delete the entire data table Turn on Limit Table display for the active trace Set Query the Limit Testing to Off 0 or On 1 Query the results of the latest limit test Pass 0 and Fail 1 Set Query Limit Table line i to Xbegin f1 Xend f2 Y1 and Y2 Set Query Limit Table index to i Insert a new line in the limit table Delete a line from the limit table Delete the entire limit table Set Query the Audio Limit Fail Alarm to Off 0 or On 1 description Set Query Averaging to Off 0 or On 1 Set Query the Number of Averages to 2 lt i lt 32000 Set Query the Averaging Type to RMS 0 Vector 1 or Peak Hold 2 Set Query the Averaging Mode to Linear 0 or Exponential 1 Set Query the Overlap to x percent 0 lt x lt 100 0 description A Set Query Source Type to Off 0 SIne 1 2 Tone 2 Noise 3 or Chirp 4 Set Query the Level of sine tone 1 tone 2 noise chirp i 0 4 to x mV Set
262. ress the HELP key ENN OPERATION REAR PANEL IEEE 488 GPIB Connector Parallel Printer Connector POWER ENTRY MODULE The power entry module is used to fuse the AC line select the line voltage and block high frequency noise from entering or exiting the instrument Refer to the first page of this manual for instructions on selecting the correct line voltage and fuse IEEE 488 CONNECTOR The 24 pin IEEE 488 connector allows a computer to control the SR770 via the IEEE 488 GPIB instrument bus The address of the instrument is set in the SETUP GPIB menu Also a GPIB plotter with HPGL compatible graphics may be connected to the IEEE 488 port In this case the SR770 will control the plotter to generate plots of the screen graph Use the SETUP PLOTTER menu to configure the SR770 for use with a GPIB plotter RS232 CONNECTOR The RS232 interface connector is configured as a DCE transmit on pin 3 receive on pin 2 The baud rate parity and word length are programmed from the SETUP RS232 menu To connect the SR770 to a PC serial adapter which is usually a DTE use a straight thru serial cable 3 12 Power Entry Module PC Keyboard Connector RS 232 Connector Also a serial plotter with HPGL compatible graphics may be connected to the RS232 port The SR770 will drive the plotter to generate plots of the Screen graph Use the SETUP PLOTTER menu to configure the SR770 for use with a serial plotter PARALLE
263. riggering is on then the Trigger indicator flashes on whenever a time record is triggered Trg Wait indicates that the unit is in triggered mode and is waiting for a trigger to occur Triggers received while acquiring data from a previous trigger are ignored Armed Arm Wait If triggering is on the Armed indicator is on whenever the unit is armed and awaiting a trigger Arm Wait means that the unit is in manual arming Mee OPERATION EN mode and awaiting an arm command either from the front panel or via the computer interfaces GPIB RS232 Flashes when there is activity on the computer interfaces This does not flash for printer or plotter activity SRQ This indicator is on whenever a GPIB Service Request is generated by the SR770 SRQ stays on until a serial poll is completed REM This indicator is on when the front panel is locked out by a computer interface No front panel adjustments may be made To return the unit to local control if allowed press the HELP key Pass Fail This indicates whether a trace passes or fails a limit table test ERR Flashes whenever there is a computer interface error such as illegal command or out of range parameter is received This does not flash for a printer or plotter error 3 7 HV The High Voltage indicator turns on whenever an input greater than 50 V is detected The analyzer immediately switches in an attenuator to protect the input circuitry Any attempt to set the inpu
264. rs Connector Female Machined Part Fans amp Hardware 7 15 EN PARTS LST DSP Logic Board Parts List REF SRS PART VALUE C 301 5 00134 529 _ 1007 C302 5 00023 529 10 C303 5 00023 529 1U C304 5 00127 524 2 20 C305 5 00127 524 2 20 306 5 00134 529 100P C 501 5 00100 517 2 20 C502 5 00100 517 2 20 C505 5 00148 545 1000P C506 5 00148 545 10007 C507 5 00148 545 1000P C508 5 00148 545 1000P C509 5 00148 545 1000P C510 5 00148 545 10007 C513 5 00148 545 10007 C514 5 00003 501 10 C515 5 00134 529 100P C516 5 00023 529 1U C517 5 00023 529 1U C518 5 00023 529 1U C519 5 00023 529 1U C520 5 00023 529 1U C 521 5 00023 529 10 C522 5 00023 529 10 C523 5 00023 529 10 C524 5 00023 529 10 C525 5 00023 529 10 C526 5 00023 529 1U C527 5 00023 529 10 C528 5 00100 517 2 20 C529 5 00100 517 2 20 530 5 00100 517 2 20 531 5 00100 517 2 20 C532 5 00127 524 2 20 C533 5 00134 529 100P C534 5 00127 524 2 20 C540 5 00134 529 100P C 541 5 00219 529 010 C542 5 00134 529 100P C543 5 00003 501 10 C 601 5 00127 524 2 20 C602 5 00127 524 2 20 C603 5 00127 524 2 20 C604 5 00127 524 2 20 C605 5 00035 521 470 C606 5 00035 521 470 C607 5 00023 529 10 C608 5 00023 529 10 C609 5 00023 529 10 DESCRIPTION Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 50V 20 Rad Capacitor Tantalum 50V 20 Rad Cap Monolythic Ce
265. ry hard in the time domain are very easy in the frequency domain Take harmonic distortion It s hard to quantify the distortion by looking at a good sine wave output from a function generator on an oscilloscope When the same signal is displayed on a spectrum analyzer the harmonic frequencies and amplitudes are displayed with amazing clarity Another example is noise analysis Looking at an amplifier s output noise on an oscilloscope basically measures just the total noise amplitude On a spectrum analyzer the noise as a function of frequency is displayed It may be that the amplifier has a problem only over certain frequency ranges In the time domain it would be very hard to tell Many of these types of measurements used to be done using analog spectrum analyzers In simple terms an analog filter was used isolate frequencies of interest The remaining signal power was measured to determine the signal strength in certain frequency bands By tuning the filters and repeating the measurements reasonable spectrum could be obtained The FFT Analyzer An FFT spectrum analyzer works in an entirely different way The input signal is digitized at a high sampling rate similar to a digitizing oscilloscope Nyquist s theorem says that as long as the sampling rate is greater than twice the highest frequency component of the signal then the sampled data will accurately represent the input 2 1 signal In the SR770 sampling occurs at 2
266. ry to complete the performance tests The suggested equipment or its equivalent should be used 1 Frequency Synthesizer Freq Range 1 Hz to 1 MHz Freq Accuracy better than 5 ppm Amplitude Accuracy 0 2 dB from 1 Hz to 100 kHz Harmonic Distortion lt 65 dBc Spurious lt 55 dBc Recommended SRS DS345 AC Calibrator Freq Range 10 Hz to 100 kHz Amplitude 1 mV to 10V Accuracy 0 1 External phase locking capability Recommended Fluke 5200A Low Distortion Sine Oscillator Freq Range 1 Hz to 100 kHz Harmonic Distortion lt 90 dBc 20 kHz lt 80 dBc lt 100 kHz Recommended Krohn Hite 4400A Feedthrough Terminations Impedance 500 6 3 PERFORMANCE TESTS Warm Up The analyzer should be turned on and allowed to warm up for at least an hour before any tests are performed The self test does not require any warm up period It is necessary to turn the unit off and on to preset it As long as the unit is powered on immediately this will not affect the test results The Auto Offset feature must be left enabled On Disabling the Auto Offset may invalidate the results of some tests The Test Record Make a copy of the SR770 Performance Test Record at the end of this section Fill in the results of the tests on this record This record will allow you to determine whether the tests pass or fail and also preserve a record of the tests If A Test Fails If a test fails you should check the settings a
267. s annotated the same way as the single trace The left edge center and right edge of the graph are labelled directly below the graph When displaying spectral data with no horizontal expansion these values are the Start Center and Stop frequencies of the frequency span in use When displaying time records these values are the Start Middle and End of the time record These times are always relative to the start of the time record they do not reflect any trigger delay which may be programmed To expand a graph use the SCALE menu When the display is expanded in the horizontal axis the labels reflect the displayed span and time not the actual acquisition span and time record Expanded traces have an EXPAND indicator below the right hand edge of the graph as shown below The Top reference is the Y value of the upper edge of the graph The units can be Volts dBVolts or EU user defined engineering units The Vertical Hz 37 5 kHz 20dbV 20 dB div Wndo BMH s Live LogMag Spec 0 50 kHz 3 5 OPERATION EH Format Marker 100 kHz Marker Width eed ie LogMag Spec 1 Spot Marker Seeks Mean Grid ewe 100 kHz Div Scrn 548 i scale is shown as the number of dB Volts or EU per division This value is changed whenever the vertical scale is adjusted The Window Function for the displayed data is shown below the graph In the case of a recalled graph this windo
268. s in these status bytes will generate a single SRQ Another SRQ from ERR FFT or ESB can only be generated after clearing the ERR FFT or ESB bits in the Serial Poll status byte To clear these bits ALL enabled bits in the ERR FFT or ESB status bytes must be cleared The controller should respond to the SRQ by performing a serial poll to read the Serial Poll status byte to determine the requesting status bit Bit 6 SRQ will be reset by the serial poll For example to generate a service request when a TRIGGER occurs bit 0 in the FFT Status Enable register needs to be set FFTE 1 command and bit in the Serial Poll Enable register must be set SRE 8 command When a trigger occurs bit 0 in the FFT Status byte is set Since bit 0 in the FFT Status byte AND Enable register is set this ALSO sets bit 3 FFT in the Serial Poll Status byte Since bit 3 in the Serial Poll Status byte AND Enable register is set an SRQ is generated Bit 6 SRQ in the Serial Poll Status byte is set Further triggering will not generate another SRQ until the TRIGGER status bit is cleared The TRIGGER status bit is cleared by reading the FFT Status byte with FFTS Presumably the controller is alerted to the trigger via the SRQ performs a serial poll to clear the SRQ does something in response to the trigger read data for example and then clears the TRIGGER status bit by reading the FFT status register A subsequent trigger will then generate another SRQ STA
269. s amplitude and frequency SOURCE Configure Source Note The SR770 Source has an output impedance of less than 5 0 The source can drive 50 load to full amplitude The source is calibrated with a high impedance load This key turns the source off The output is held at OV This key sets the source output to sinewave The output is a low distortion sine wave for general purpose gain distortion and signal noise measurements The sinewave can be synchronous with the FFT i e sine waves can be generated at exact bin frequencies of the FFT This can eliminate windowing effects in the measured amplitude and phase Press Configure Source to set the sine parameters This key sets the source output to two tone The output is the sum of two low distortion sine waves for intermodulation distortion tests IMD Each tone has independent frequency and amplitude settings Press Configure Source to set the two tone parameters This key sets the source output to noise Broadband noise is useful for characterizing circuits mechanical systems or even the audio response of an entire room White noise provides equal amplitude per root Hz from 0 to 100 4 50 een SOURCE MENU Chirp Configure Source kHz regardless of the measurement span White noise is useful in electronic applications Pink noise rolls off at 3 dB oct providing equal amplitude per octave Pink noise is preferred in audio applications Press lt Conf
270. s mode The MARKER MAX MIN key only searches the data which is on the screen If the max min value occurs at more than one location then the one closest to the left edge is found PRINT PRINT will print the currently displayed screen to a printer attached to the rear panel parallel printer port The entire screen including text and menus is printed The time and date will also be printed The printer type needs to be configured in the 3 11 SYSTEM SETUP menu before using PRINT A Printing in Progress message will appear on the Screen while printing occurs Pressing lt backspace will abort the printout No other front panel operations may be performed until printing is completed If no printer is attached or there is a printer error then the print operation is aborted after about 10 seconds A Print Aborted message will appear briefly on the screen HELP HELP provides on screen help with any key or soft key Pressing HELP followed by any key will display information about the function or use of that key HELP with a soft key will describe the menu item next to the soft key Pressing another key will exit the help screen The PRINT key is the one key for which no help is available Pressing PRINT at any time will print the screen including the help screens LOCAL When a host computer places the unit in the REMOTE state no keypad or knob input is allowed To return to front panel operation p
271. s not reduce the actual noise floor With a sufficient number of averages a very good approximation of the actual random noise floor can be displayed Since RMS averaging involves magnitudes only displaying the real or imaginary part or phase of an RMS average has no meaning The RMS average has no complex information Vector Averaging Vector averaging averages the complex FFT spectrum The real part is averaged separately from the imaginary part This can reduce the noise floor for random signals since they are not phase coherent from time record to time record Vector averaging requires a trigger The signal of interest must be both periodic and phase synchronous with the trigger Otherwise the real and imaginary parts of the signal will not add in phase and instead will cancel randomly With vector averaging the real and imaginary parts as well as phase displays are correctly averaged and displayed This is because the complex information is preserved Peak Hold Peak Hold is not really averaging rather the new spectral magnitudes are compared to the previous data and if the new data is larger then the new data is stored This is done on a frequency bin by bin basis The resulting display shows the peak 2 7 magnitudes which occurred in the previous group of spectra Peak Hold detects the peaks in the spectral magnitudes and only applies to Spectrum PSD and Octave Analysis measurements However the peak magnitu
272. s on real time harmonic sideband and band analysis as well as Limit and Data tables for the active trace Note When real time analysis functions or Limit tables are active the trace update rate may significantly slow down No harmonic sideband or band analysis is available when measuring Time Record or Octave Analysis or when displaying Phase ANALYZE Data Table Limit Table This key turns off any real time harmonic sideband or band analysis If no real time analysis is on then this key turns on harmonic analysis for the active trace The harmonic analysis submenu is displayed and the marker frequency will be entered into the fundamental frequency entry field If any real time analysis is already on then this key simply displays the harmonic analysis submenu without change The harmonic submenu is described in the following pages When harmonic analysis is on the harmonic level rms sum of the magnitudes of the harmonic frequency bins and Total Harmonic Distortion or THD the harmonic level divided by the fundamental magnitude are displayed in the upper left corner of the graph Only those harmonics which appear within the frequency span figure into the calculations of harmonic power If no real time analysis is on then this key turns on sideband analysis for the active trace The sideband analysis submenu is displayed and the marker 4 29 ANALYZE MENU Se Band Data Table Limit Table frequ
273. segment between the pair of points Xbegin Y1 and Xend Y2 as shown below The segment values between the endpoints are calculated for the displayed frequency span Xend Y2 n 1 A segment may be defined as either an upper or lower limit Trace data values which are greater than an upper or less than a lower limit cause the test to fail Note Y values are entered without units They are simply numbers When the display units are changed the limit table is unaffected and the limit tests will compare the trace data in the new units with the old limit table values Be 4 40 ANALYZE MENU careful to use the limit tables only when the entered Y values match the displayed units Trace data is compared with the limits only over the range of X values or frequencies for which limit segments have been defined Segments do not have to cover the entire span or be connected The four segments shown below comprise a legitimate limit table Frequencies not included within any segment are not tested If both segments 2 and 4 are upper limits then the lower limit segment 4 is tested Segment 3 2 Segment 1 Segment 2 Segment 4 Note Limit segments are graphed on the display In the case of logarithmic X axis the segments are still displayed graphically as a straight line This graphical line is the limit Thus a given limit test may give different results depending upon the type of X axis disp
274. sing the COPR command The parameter selects the aperture for the d dx operation and is required if the operation is d dx may be omitted for all other operations The aperture is 6 25 150 5 25 121 4 25 122 2 75 151 or 1 25 150 CARG 7 i The CARG command sets or queries the argument type The parameter i selects Constant i 0 Other Graph i 1 or 2 f 0 2 CONS x The CONS command sets or queries the constant argument The parameter x is a real number CMRK The CMRK command sets constant argument to the Y value of the marker 5 21 REMOTE PROGRAMMING FRONT PANEL CONTROLS STRT STCO PRSC ACTG i ARNG i AUTS g The STRT command starts data acquisition This function is the same as pressing the START key If the analyzer is already in the run mode then any average is reset The STCO command pauses or continues data acquisition This function is the same as pressing the PAUSE CONT key If the analyzer is running then the STCO command pauses the analyzer If the analyzer is paused then STCO resumes data acquisition without resetting any average If the analyzer is stopped after a completed linear average the STCO will do nothing since there is nothing to resume The PRSC command will print the currently displayed screen to a printer attached to the rear panel parallel printer port This function is the same as the PRINT key The printer type needs to
275. sk containing data from the drive and insert a scratch disk This test will check the controller format the disk and read and write data to the disk The entire test takes approximately 2 minutes 4 72 Men SYSTEM MENU EHI RS 232 Test Memory Test Main Mem Video Mem Screen Test Printer Test Printer HP EPSON Screen Dump Print String y DSP Test i Return Use the Return function to skip this test and return to the previous menu Pressing this key activates the RS232 test screen A special loop back adapter is required to complete this test The loop back adapter is simply a mating connector with pins 2 and 3 connected so characters transmitted by the interface will be received by the instrument The Memory Test key activates a memory test sub menu Select the desired memory test Main Memory Video Memory Pressing this key tests the program ROM and data RAM on the CPU board The data acquisition memory is not tested See the Test and Calibration section for more information on testing the data acquisition hardware Pressing this key tests the video display RAM A video pattern will scroll through the display while the test is done Return The Return key will return to the Test menu This key displays a test pattern on the screen The Printer Test key activates a sub menu Printer Type Screen Dump Print String graphics mode Return The Printer Type key selec
276. srupts the phase Go to the Display menu Display the phase as a full screen graph The phase spectrum of the chirp is quite complicated looking The phase changes quite quickly from 180 to 180 degrees Many filters exhibit similar large phase shifts Sometimes it is more informative to view the phase spectrum as unwrapped phase Unwrapping attempts to display the phase as a continuous unbounded curve instead of from 180 to 180 degrees Go to the Measure menu Select the Calculator menu Select the unwrap operation Do the calculation Scale the resulting graph The phase curve is now a much simpler curve varying between very large phases Unwrapping can make complicated phase curves more understandable if there is a relationship between adjacent frequency bins The derivative of the phase with respect to frequency x axis is the group delay Do the derivative calculation This brings up a submenu to select the aperture The aperture as a percentage of 400 bins over which the derivative is calculated needs to be selected Choose a narrow aperture The resulting group delay curve shows a linear group delay over several regions of the spectrum Group delay is actually 06 00 where is in radians To convert the numerator to radians multiply by 26 360 To convert from d dx to d do divide the curve by 26 linewidth Altogether we need to divide the curve by 1 360 linewidth 1 45 ENN GETTING STARTED Press
277. st The Test submenu allows the user to test various features of the SR770 such as the keypad knob screen memory etc Use the More softkey to select the second test menu screen SYSTEM Keyboard Test RS 232 Test c Memory Tes RS 232 Test Screen Test Printer um gt DSP This key activates the keypad test screen The keypad test screen displays a map of the keypad with each key represented by a small square Pressing each key will highlight the corresponding square When all squares are highlighted the test is complete This key activates the keyboard test screen Characters typed on an attached PC keyboard in PC or 8088 mode will be displayed on the test screen If the displayed characters are accurate then the keyboard interface is functioning and the keyboard is configured correctly If not check that the keyboard is in the correct mode Many keyboards have a switch on the bottom to select PC 8088 or AT 80286 mode This key activates the knob test screen A circle with a marker is displayed Select one of the 4 speeds displayed in the menu Turning the knob will cause the marker to move around the circle verifying knob action and direction Using speed 1 or 2 is best when checking direction of movement Pressing this key activates the disk drive test screen Continuing with this test will destroy any data on the disk currently in the drive Therefore remove any di
278. stable but seemingly random To measure the phase response of a device under test a calibrated source phase curve is required The Auto Phase function measures the current phase spectrum and stores it in memory This reference phase spectrum is then subtracted from subsequent phase spectra to remove the phase of the chirp source After Auto Phase the phase spectrum will be 0 across the entire span If a device is inserted between the source and the input the phase spectrum will show the phase response curve of the device This is similar to a relative phase measurement using a 2 channel analyzer except that the output reference phase is measured and stored Auto Phase is removed whenever the span is changed or the source type is changed Remember Auto Offset will interrupt the input time records and change the absolute phase Turn Auto Offset off when measuring phase with the source Do not use Auto Phase and measure the phase of another signal source This key turns the Source Cal on and off The source is digitally synthesized and passes through an output reconstruction filter The spectrum of broadband outputs such as chirp exhibit the passband ripple of this filter Source Cal adjusts the input calibration to compensate for the output reconstruction filter ripple The spectrum of the chirp output will appear flat when Source Cal is on If a device is inserted between the source and the input the spectrum will show the amplitude trans
279. steep As a result the Hanning window can limit the performance of the analyzer when looking at signals close together in frequency and very different in amplitude Flattop The Flattop window improves on the amplitude accuracy of the Hanning window Its between bin amplitude variation is about 02 dB However the selectivity is a little worse Unlike the Hanning the Flattop window has a wide pass band and very steep rolloff on either side Thus signals appear wide but do not leak across the whole spectrum BMH The BMH window is a very good window to use with this analyzer It has better amplitude accuracy about 0 7 dB than the Hanning very good selectivity and the fastest filter rolloff The filter is steep and narrow and reaches a lower attenuation than the other windows This allows signals close together in frequency to be distinguished even when their amplitudes are very different If a measurement requires the full dynamic range of the analyzer then the BMH window is probably the best one to use een ANALYZERBASICS AVERAGING The SR770 analyzer supports several types of averaging In general averaging many spectra together improves the accuracy and repeatability of measurements RMS Averaging RMS averaging computes the weighted mean of the sum of the squared magnitudes FFT times its complex conjugate The weighting is either linear or exponential RMS averaging reduces fluctuations in the data but doe
280. t THRU HOLE 50907 1 00232 150 52 PLCC TH Socket THRU HOLE U 101 3 00354 360 80C186 12 Integrated Circuit Surface Mount Pkg U 201 3 00340 340 74 15373 Integrated Circuit Thru hole Pkg U 202 3 00340 340 _ 7400 5373 Integrated Circuit Thru hole Pkg U 203 3 00340 340 74 15373 Integrated Circuit Thru hole Pkg U 204 3 00341 340 7400 5245 Integrated Circuit Thru hole Pkg U 205 3 00341 340 74ALS245 Integrated Circuit Thru hole Pkg U 206 3 00342 340 7400 5138 Integrated Circuit Thru hole Pkg U 207 3 00343 340 74 1532 Integrated Circuit Thru hole Pkg U 208 3 00344 340 74ALS08 Integrated Circuit Thru hole Pkg U 401 3 00299 341 gt 32KX8 70L STATIC RAM I C U 402 3 00299 341 32KX8 70L STATIC RAM I C U 403 3 00299 341 32KX8 70L STATIC RAM I C U 404 3 00299 341 32KX8 70L STATIC RAM I C U 501 3 00342 340 74ALS138 Integrated Circuit Thru hole Pkg U 502 3 00342 340 74ALS138 Integrated Circuit Thru hole Pkg U 503 3 00342 340 7400 5138 Integrated Circuit Thru hole Pkg U 504 3 00049 340 74HC74 Integrated Circuit Thru hole Pkg U 505 3 00347 340 7415148 Integrated Circuit Thru hole Pkg U 506 3 00259 340 7AHCT373 Integrated Circuit Thru hole Pkg U 601 3 00049 340 7AHC74 Integrated Circuit Thru hole Pkg U 602 3 00348 340 74HC20 Integrated Circuit Thru hole Pkg U 603 3 00265 340 74HC595 Integrated Circuit Thru hole Pkg U 606 3 00044 340 74HC244 Integrated Circuit Thru hole Pkg U 607 3 00046 340 74HC374 Int
281. t range to a setting which would remove this attenuator will not be allowed until the input signal is reduced to a safe level ALT Indicates that the ALTERNATE keypad is in use The ALTERNATE keypad uses the alphabetic legends printed below each key To enter the ALT mode press the ALT key once Pressing the keys will now enter alphabetic characters into the active entry field The 0 9 lt and ALT have the same function in the ALTERNATE keypad To return to the normal keypad press the ALT key again OPERATION KEYPAD CONTROL SYSTEM E LOCAL F ACTIVE START PAUSE MARKER T CONT A B TRACE MENU H K L N 5 T SYSTEM STORE RECALL Y 2 7 8 9 ALTO RANGE G 4 5 6 AUTO SCALE J E M MOOE 0 SPAN Q R 5 D ALT 4 EXP gt CENTER ENTAY U V X MARKER NORMAL AND ALTERNATE KEYS The normal key definitions are printed on each key quantity units window type and calculator In addition each key also has an alternate definition DISPLAY Sets the display format marker printed below it The ALT key toggles the keypad on off and grid modes between the two definitions The ALT screen indicator is on when the alternate definitions are in INPUT Configures the signal inputs sets use The 0 9 lt and ALT keys have the manual input range and trigger the same definition in both modes
282. tal ground noise U1 provides power up and power down reset The 24 VDC brushless fan runs from the 18V unregulated supply CIRCUIT DESCRIPTION EN DSP LOGIC BOARD OVERVIEW The DSP LOGIC BOARD takes a digital input from the A D Converter on the Analog Input Board and performs all of the computations related to the measurement before it is displayed on the screen This includes digital heterodyning frequency shifting digital filtering and downsampling Fast Fourier Transforming averaging and output display processing scaling magnitude calc log sqrt etc These functions are implemented within a system comprised of four functional blocks the Digital Signal Processors DSP s the Trigger Processor the Timing Signal Generator and the Interface Through the use of highly efficient algorithms the system is capable of real time heterodyning and filtering and can compute a 512 point FFT in under 1 5 ms FFT s can be computed on the incoming data faster than the time it takes to complete a time record This is what accounts for the extremely high 100 kHz real time bandwidth of the SR770 The fifth functional block is the source generator The source is synthesized filtered and attenuated before being passed to the output connector DSP PROCESSORS The SR770 utilizes two Motorola 24 bit DSP56001 DSP Chips The two DSP s are configured almost identically with minor differences reflecting the specific fun
283. tatus byte the FFT status byte and the error status byte Upon power on the SR770 may either clear all of its status enable registers or maintain them in the state they were in on power down The PSC command determines which action will be taken The status bits are set to 1 when the event or state described in the tables below has occurred or is present SERIAL POLL bit name usage STATUS BYTE 0 SCN No measurements in progress 1 IFC No command execution in progress 2 ERR An unmasked bit in the error status byte has been set 3 FFT An unmasked bit in the FFT status byte has been set 4 MAV The interface output buffer is non empty 5 ESB An unmasked bit in the standard status byte has been set 6 SRQ SRQ service request has occurred 7 Unused The ERR FFT and ESB bits are set whenever any bit in both their respective status bytes AND enable registers is set Use the SRE ESE ERRE and FFTE commands to set enable register bits The ERR FFT and ESB bits are not cleared until ALL enabled status bits in the Error FFT and Standard Event status bytes are cleared by reading the status bytes or using CLS Using STB to read the Serial Poll Status Byte A bit in the Serial Poll status byte is NOT cleared by reading the status byte using STB The bit stays set as long as the status condition exists This is true even for SRQ SRQ will be set whenever the same bit in the serial poll status byte AND serial poll enable register is set This is i
284. tches to dual trace format with the spectrum on top and the limit table listed below This moves the marker to the peak of the spectrum and measures the fundamental frequency Let s define an upper limit for the 1 kHz peak Highlight the upper X Value menu field Enter a frequency below the signal frequency Highlight the lower X Value menu field Enter a frequency higher than the signal frequency As with data tables it is also possible to copy the marker X location into the X value fields But this time we want frequencies above and below the peak so we entered them numerically 1 24 eee GETTING STARTED EN 9 11 Press Y Values Press 5 Enter Press Y Values Press 5 Enter Press More Press Audio Alarm Press Audio Alarm Press Return Press Y Values Press 2 Enter Press Y Values Press 2 Enter Press Table Index Press 1 Enter Highlight the upper Y values menu field Enter a value somewhat less than the signal peak Highlight the lower Y values menu field Enter a value somewhat less than the signal peak Notice that small line segment is drawn on the display This line starts at Xbegin Y 1 and ends at Xend Y2 and represents a limit segment If the data exceeds this limit since it is an upper limit then the FAIL indicator will flash at the bottom of the screen The FAIL indicator should be flashing now Display the second
285. te definitions follow this section CLS ESE i i ESR i i j STB i PSC i ERRE i 0 ERRS i FFTE i 6j FFTS i The CLS command clears all status registers The ESE i command sets the standard status byte enable register to the decimal value i 0 255 The ESE i j command sets bit i 0 7 to j 0 or 1 The ESE command queries the value 0 255 of the status byte enable register The ESE i command queries the value 0 or 1 of bit i The ESR command queries the value of the standard status byte The value is returned as a decimal number from 0 to 255 The ESR i command queries the value 0 or 1 of bit i 0 7 Reading the entire byte will clear it while reading bit i will clear just bit i The SRE i command sets the serial poll enable register to the decimal value i 0 255 The SRE i j command sets bit i 0 7 to 0 or 1 The SRE command queries the value 0 255 of the serial poll enable register The SRE i command queries the value 0 or 1 of bit i The STB command queries the value of the serial poll byte The value is returned as a decimal number from 0 to 255 The STB i command queries the value 0 or 1 of bit i 0 7 Reading this byte has no effect on its value The PSC command sets the value of the power on status clear bit If i 1 the power on status clear bit is set and all status registers and enable registers are cleared
286. tered frequency will be rounded to the nearest multiple of 15 26 mHz Remember the output is periodic over the input time record only if the frequency is a multiple of the linewidth Source triggering will not result in a stable phase for random frequencies These keys activate the level entry fields for tones 1 and 2 The output level is expressed in mVpk The level may be entered in either mVpk or dBVpk The knob always adjusts the level in mVpk The resolution is 1 mV for levels greater than 100 mV and 0 1 mV for levels less than 100 mV The maximum level for each tone is 500 mV This key returns the main source selection menu 4 53 SOURCE M Configure Noise The Configure Noise submenu allows the noise level and type to be set SOURCE Pink Noise Level Source Cal ot o Configure Source Noise Type Return Noise Type This key selects the noise type White noise provides equal noise density Volts OHz from 0 to 100 kHz regardless of the measurement span The spectrum of white noise appears flat with constant power spectral density PSD Pink noise rolls off at 3 dB oct providing equal power per octave of frequency The spectrum of pink noise appears flat when measured using octave analysis Since the signal is noise and random windowing is required to achieve a meaningful spectrum Source triggering is not useful since there is no stable phase information in the S
287. than old data Averaging takes place according to the formula Averagey New Spectrum 1 N Averagey 4 N 1 N where N is the number of averages Exponential averaging continues indefinitely To stop the averaging use the PAUSE CONT key When paused the PAUSE CONT key will resume the averaging while the START key will reset the average before restarting Exponential averages grow for approximately the first 5N spectra until the steady state values are reached Once in steady state further changes in the spectra are detected only if they last sufficiently long Make sure that the number of averages is not so large as to eliminate the changes in the data that might be important Overlap This key activates the Overlap Percentage entry field For most frequency spans the SR770 can compute the FFT in less time than it takes to acquire the time record With 096 overlap the analyzer computes one FFT per time record and then waits until the next time record is complete before computing the next FFT The update rate is no faster than one spectra per time record With narrow spans this can be quite slow With overlap processing the analyzer does not wait for the next complete time record before computing the next FFT Instead it uses data from the previous time record as well as data from the current time record to compute the next FFT This speeds up display updates as well as reduces the variations due to windowing Remember
288. than terminators In addition the host program must read exactly the correct number of bytes 800 bytes plus the last line feed While a binary dump is in progress the analyzer will not respond to any other queries and the display will not update 5 23 REMOTE PROGRAMMING BDMP g i If the host program does not start reading the points within 1 second or pauses for 1 second while reading the binary dump will be aborted The BDMP command sets or queries the auto binary dump mode for trace g The parameter i selects binary dump off 0 0 or on 0 1 When auto binary dump mode is on whenever new data becomes available the data will be dumped in binary format over the GPIB interface in the same format as the response to the SPEB command Auto binary dump is not available over the RS232 interface While a binary dump is in progress the analyzer will not respond to any other queries and the display will not update When using the BDMP g 1 command the host interface must be capable of binary transfer i e accepting line feeds and carriage returns as data rather than terminators In addition the host program must read exactly the correct number of bytes 800 bytes for normal spectra 30 or 60 bytes for 15 or 30 band octave analysis If the host program does not start reading the points within 1 second of the data becoming available or pauses for 1 second while reading the binary dump will be aborted and the
289. the same as the previous segment s The only thing you need to edit is the value of Y2 and your new segment is finished But let s go on to define a noise floor limit Enter a segment which is between harmonics In this case between 2 2 and 2 8 kHz This is representative of the noise floor Define an upper limit a little above the noise floor In this case we define an upper noise limit of 90 dB There should now be a horizontal segment above the noise floor between 2 2 and 2 8 kHz The limit test should still PASS This switches the noise limit from an upper limit to a lower limit Since the data will now be below the lower limit the test will FAIL Display the second limits menu Set limit testing to OFF It is possible to display the limit table without testing taking place This is helpful when a lot of the X values on the graph have defined limits The testing can slow down the response of the analyzer noticeably It is simpler to define the limits with testing off Show the Display menu Choose the Single trace display format This removes the limit table display and restores the screen to a single trace display No testing occurs when the limit table is not displayed 1 26 eee GETTING STARTED EN USING TRACE MATH The Calculator submenu allows the user to perform arithmetic calculations with the trace data Operations are performed on the entire trace regardless of graphical expansion Calculations
290. the Analog Input Board locally 15V is generated for most of the analog IC s A dedicated 15V supply is also generated for the front end amplifier 5V is generated for the A D Converter as well as a digital 5V for the digital IC s that provide timing signals to the A D Lastly another 5V supply is generated for all other digital logic and 12V for relays eee PARTS LIST CPU Board Parts List REF SRS PART VALUE DESCRIPTION BT701 6 00001 612 BR 2 3A 2PIN PC Battery C 101 5 00177 501 Capacitor Ceramic Disc 50V 1096 SL C 102 5 00215 501 20 Capacitor Ceramic Disc 50V 1096 SL C 103 0 00772 000 1 5 WIRE Hardware Misc C 501 5 00215 501 20 Capacitor Ceramic Disc 50V 10 SL C 601 5 00033 520 470 Capacitor Electrolytic 16V 2096 Rad C 602 5 00012 501 330P Capacitor Ceramic Disc 50V 1096 SL C 603 5 00012 501 330P Capacitor Ceramic Disc 50V 1096 SL C 701 5 00064 513 00470 Capacitor Mylar Poly 50V 596 Rad C 704 5 00012 501 330P Capacitor Ceramic Disc 50V 1096 SL C 705 5 00012 501 330P Capacitor Ceramic Disc 50V 1096 SL C 706 5 00061 513 0010 Capacitor Mylar Poly 50V 596 Rad C 801 5 00178 501 62 Capacitor Ceramic Disc 50V 1096 SL C 802 5 00178 501 62 Capacitor Ceramic Disc 50V 1096 SL C 803 5 00100 517 2 20 Capacitor Tantalum 35V 2096 Rad C 804 5 00225 548 1U AXIAL Capacitor Ceramic 50V 80 20 Z5U AX C 805 5 00100 517 2 20 Capacitor Tantalum 35V 2096
291. this test in the test record at the end of this section 6 10 eee PERFORMANCE TESTS 5 Amplitude Linearity This test measures the amplitude linearity This tests how accurately the analyzer measures a signal smaller than full scale Setup We will use the frequency synthesizer to provide an accurate frequency and the AC calibrator to provide a sine wave with an exact amplitude Connect the output of the frequency synthesizer to the phase lock input of the calibrator Connect the output of the AC calibrator to the A input of the analyzer Be sure to use the appropriate terminations where required Set the Synthesizer to Set the AC Calibrator to Function Sine Frequency 1 kHz Frequency 1 kHz Amplitude 6 3021 Vrms Amplitude 0 5 Vrms Voltage Off Offset off or OV Phase Lock On Sweep off Sense Internal Modulation none Procedure 1 PRESET Turn the analyzer off wait a few seconds then back on with the lt key pressed 2 Press the keys in the following sequence MEAS lt Window gt lt Flattop gt FREQ lt Span gt 1 5 kHz lt Center Freq gt 1 lt kHz gt AVERAGE lt Number of Averages gt 2 0 Enter lt Averaging gt Select On INPUT lt Input Range gt 2 2 lt dBV gt START AUTO SCALE MARKER MAX MIN 3 For each of the amplitudes listed below perform steps 3a through 3c 6 11 PERFORMANCE TESTS AC Calibrator Amplitudes 6 3021 Vrms 1 1207
292. tions require no argument Unwrap attempts to display the phase as a continuous curve rather wrapping around at 180 rads Phase response curves as measured using the chirp source are generally more meaningful unwrapped The derivative function d dx differentiates the curve with respect to the x axis in frequency bins To convert to d do divide the result by 26 times the linewidth 4 13 MEASURE MENU M Do Calc Argument Type Argument Marker to Arg cu Argument Marker to Arg Return Pressing this key starts the actual calculation The Calculating message appears below the graph while calculations are in progress The calculation uses the operation specified by the Operation key and uses the argument chosen by the Argument keys Note that many operations will require an AutoScale to display the result on the graph When the operation is d dx a submenu will appear to select the aperture The aperture expressed as a percentage of the span is the how wide an area is considered when calculating the derivative If the curve is noisy a wide aperture may be required to yield meaningful results The Argument Type function selects between a constant argument 260 and a second data trace A constant argument adds or subtracts a constant or multiplies or divides by a constant Choosing uses the argument 2 frequency for each frequency bin The other graph option uses the other inacti
293. tor CIRCUIT DESCRIPTION POWER SUPPLY BOARD CAUTION Dangerous voltages are present on this circuit board whenever the instrument is attached to an AC power source and the front panel power switch is on Always disconnect the power cord and wait at least one minute before opening the unit Check the LED at the front edge of the power supply board The unit is safe only if the LED is OFF If the LED is ON then DO NOT attempt any service on the unit UNREGULATED POWER SUPPLIES A power entry module with RF line filter is used to configure the unit for 100 120 220 or 240 VAC The line filter reduces noise from the instrument and reduces the unit s susceptibility to line voltage noise R1 is an inrush limiter to limit the turn on current and TS1 is a thermal switch which will interrupt the AC line if the heat sink temperature rises to 50 C Bridge rectifiers are used to provide unregulated DC at 22V 18V and 8V Schottky diodes are used for all supplies to reduce rectifier losses Resistors provide a bleed current on all of the unregulated supply filter capacitors Because of the large capacitances in this circuit the time for the voltages to bleed to zero is about a minute after the power is turned off POWER SUPPLY REGULATORS The voltage regulators provide outputs at 5V 5V 15V 18V and 12V The 5V regulators are designed to operate with a very low drop out voltage U2 is a precision 5 00
294. tor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Comp 1 2W 5 Resistor Carbon Comp 1 2W 5 Resistor Carbon Film
295. treat the data as intrinsic values either Volts Engineering Units or degrees If a graph is showing dB then multiplying by 10 will raise the graph by 20 dB and dividing by 10 will lower the graph by 20 dB Performing a calculation on the active trace will set the File Type to Calc to indicate that the trace is not Live This is shown by the File Calc message at the lower left of the graph The analyzer continues to run but the calculated trace will not be updated To return the trace to live mode activate the trace and press the START key The File Type will return to Live There are two types of front panel keys which will be referenced in this section Hardkeys are those keys with labels printed on them Their function is determined by the label and does not change Hardkeys are referenced by brackets like this HARDKEY The softkeys are the six gray keys along the right edge of the screen Their function is labelled by a menu box displayed on the screen next to the key Softkey functions change depending upon the situation Softkeys will be referenced as the lt Soft Key gt or simply the Soft Key 1 27 The Measurement This measurement is designed to familiarize the user with the trace math capabilities We will use the SR770 Source to provide a test signal Specifically you will reference spectrum ratio a spectrum with a ENN GETTING STARTED M TRACE MATH 1 Turn the analyzer on while holding down the lt
296. ts the type of printer attached to the parallel printer port Any Epson compatible graphics printer or HP LaserJet compatible printer is supported Pressing this key will print the graphics screen on the printer This action is the same as using the PRINT key Pressing this key prints a text string to the printer If the Print String test works but the Screen Dump test fails then the printer probably does not support the Epson or HP LaserJet The Return key will return to the Test menu Pressing this key tests the two Digital Signal Processors and their data memories Pressing this key returns to the first Test submenu Pressing Return again displays the second System Setup menu 4 73 EN SYSTEM MENU 4 74 SYSTEM MENU Get Info The Get Info submenu displays various information screens which may be helpful to the user SYSTEM Get Info About the SR770 About SRS Operating Hints Command List Status Bytes Return About the SR770 This key displays the SR770 specifications About SRS This key displays information about Stanford Research Systems Inc Operating Hints This key displays information about the use of the SR770 Command List This key displays a list of the remote commands available Status Bytes This key displays an explanation of the remote programming status bytes Fundamental Constants This key displays a table of fundamental constants 4 75
297. ttings See the Default Settings list in the Menu section for a complete listing of the settings Display the Source menu Turn on the Sine output Display the Sine frequency and level Select the Sine output level Enter 3 dBV for the Sine output level Note that the Sine level can be entered in either mV pk or dBV pk Move the marker to the signal peak The marker should be centered at the 1 kHz signal and display a level of 3 dBV Select the Sine frequency When the knob is used to adjust the sine frequency the frequency resolution is equal to the linewidth of the displayed spectrum In this case since we are at full span the linewidth is 250 Hz 100 kHz 400 This always puts the sine exactly on a frequency bin of the spectrum Move the marker to the signal peak Select the Sine frequency The keypad allows random frequencies to be entered The fundamental frequency resolution of the sine source is 15 26 mHz The entered frequency will be rounded to the nearest multiple of 15 26 mHz In this case 50 01 kHz is rounded to 50 0099945 kHz only 5 5 mHz off When the knob is used again the frequency resolution returns to the linewidth and the frequency immediately jumps to the nearest multiple of the linewidth 1 33 5 Press AVERAGE Press lt Number of Averages gt Press 2 0 lt Enter gt Press Average Mode to select Exponential Press lt Averaging gt to turn on averaging Press MARK
298. uit Thru hole Pkg Crystal Crystal Crystal Crystal Wire 24 UL1007 Strip 1 4x1 4 Tin Wire Other Cable Assembly Ribbon Connector D Sub Female DESCRIPTION Capacitor Electrolytic 35V 20 Rad Capacitor Electrolytic 35V 20 Rad Capacitor Electrolytic 35V 20 Rad Capacitor Electrolytic 35V 20 Rad Capacitor Electrolytic 10V 20 Rad Capacitor Electrolytic 25V 20 Rad Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 50V 20 Rad Capacitor Electrolytic 50V 20 Rad Capacitor Ceramic Disc 50V 20 Z5U Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 20 Z5U Capacitor Ceramic Disc 50V 10 SL Capacitor Tantalum 50V 20 Rad Capacitor Tantalum 50V 20 Rad Capacitor Tantalum 50V 20 Rad Cap Mini Electrolytic 50V 20 Radial Capacitor Tantalum 50V 20 Rad Capacitor Tantalum 50V 20 Rad Cap Mini Electrolytic 50V 20 Radial Capacitor Tantalum 50V 20 Rad 7 13 EN PARTS LST REF SRS PART VALUE DESCRIPTION C 26 5 00192 542 220 MIN Cap Mini Electrolytic 50V 20 Radial C27 5 00127 524 2 20 Capacitor Tantalum 50V 20 Rad C 28 5 00192 542 220 MIN Cap Mini Electrolytic 50V 2096 Radial C 29 5 00127 524 2 20 Capacitor Tantalum 50V 2096 Rad C 30 5 00192 542 220 MIN Cap Mini Electrolytic 50V 2096 Radial C 31 5 00127 524 2 20 Capacitor Tantalum 50V 20 Rad C 32 5 00192 542 220 MIN Cap Mini Electrolytic 50V 2096 Radial C 3
299. uits When each time record finishes the next one begins without delay Any signal which is EXACTLY periodic over a time record will be the same in EVERY time record For this type of signal this has the same effect as triggering If the source sine frequency is an exact multiple of 1 34 eee GETTING STARTED EN 8 9 Press AVERAGE Press Average Type to select Vector Press SOURCE Press Configure Source Press Frequency Press 1 0 1 kHz Use the knob to set the frequency back to 10 kHz Press AVERAGE Press lt Averaging gt to turn averaging off the linewidth then the source will appear triggered This only works with the SR770 s own source since itis clocked with the same crystal timebase as the input time record A separate sine generator will invariably drift relative to the SR770 s timebase and the generator s sine frequency will drift away from an exact bin frequency To see how this works we need to vector average Go back to the Average menu Vector averaging averages the complex FFT spectrum This reduces the level of signals which are not phase coherent from time record to time record such as noise Notice that the noise floor is actually reduced but the signal and its harmonics stay the same amplitude This is because the source and its harmonics are at an exact bin frequency and are EXACTLY the same in each time record Even though the signal has a stable
300. upling gt Press STORE RECALL Press lt Save Settings gt Press lt File Name gt Press ALT Press T E S T 1 lt Enter gt Press lt Save Settings gt Press SPAN UP a number of times to change the span Press INPUT Press lt Coupling gt Press STORE RECALL Press lt Recall Settings gt Press lt Catalog gt When the power is turned on with the backspace key depressed the analyzer returns to its default settings See the Default Settings list in the Menu section for a complete listing of the settings Change the analyzer setup so that we have a non default setup to save Show the Input menu Choose DC coupling Display the Store and Recall menu Choose the Save Settings menu Now we need a file name ALT lets you enter the letters printed below each key The numbers and backspace function as normal Enter a file name such as TEST1 or any legal DOS file name Save the analyzer setup to disk using the file name specified above Change the analyzer setup again Show the Input menu Choose AC coupling Now let s recall the analyzer setup that we just saved Display the Store and Recall menu Choose the Recall Settings menu Display the disk catalog listing Note that data files have the type DAT and setting files have the type SET 1 18 een GETTING STARTED EN 8 Press MARKER 9 Press Recall Settings Pressing the MARKER key allows the knob to
301. ut sampling Sine A low distortion sine wave for general purpose gain distortion and signal noise measurements The sine source is synchronous with the FFT i e sine waves can be generated at exact bin frequencies of the FFT This can eliminate windowing effects in the measured amplitude and phase Two Tone Two low distortion sine waves can be generated simultaneously for intermodulation distortion tests IMD Each tone has independent frequency and amplitude settings Chirp The Chirp source provides an equal amplitude sine wave at each bin of the displayed spectrum Since there are 400 bins in a spectrum the chirp is the sum of 400 discrete sine waves The phases of each sine wave are arranged so that they do not add in phase and the resulting output does not peak This source is useful for measuring transfer functions quickly without having to make many discrete measurements using a single sine wave The Source Cal mode compensates for the ripple in the output filter by adjusting the input calibrations This results in a flat chirp spectrum Inserting a device under test will measure the device s amplitude transfer curve Windowing The Sine Two Tone and Chirp sources can be used with or without a window function The sine and two tone frequencies can be set at exact bin frequencies of the spectrum hence they can be exactly periodic in the time record As long as the signal to noise at the input if high windowing is
302. ut Range indicator will in characters if Auto Ranging is on AUTOSCALE Pressing AUTOSCALE will automatically set the vertical scale and translation to display the entire range of the data AUTOSCALE does not affect the horizontal scaling AUTOSCALE may be pressed at any time during or after data acquisition 3 10 AUTOSCALE only operates on the data which is displayed on the graph If the graph is expanded data corresponding to frequency or time bins which are not shown do not figure in the autoscaling calculations SPAN UP and SPAN DOWN The SPAN UP and SPAN DOWN keys increment and decrement the frequency span by a factor of 2 These keys provide a way of adjusting the span when any menu is displayed The span is adjusted with either a fixed start or fixed center frequency depending upon which frequency field was most recently activated in the FREQ menu MARKER ENTRY In the ANALYZE menu pressing this key will enter the marker frequency into the Fundamental Harmonic analysis Carrier sideband analysis Band Start and Center band analysis frequency fields This key also enters the marker frequency into the X Value field of the Data and Limit Tables MARKER MODE The MODE key in the MARKER section of the keypad brings up a menu This menu selects linked cursors in the dual trace display and allows marker offsets to be entered manually The Peak find functions are also in this menu MARKER REF T
303. ut does not update it See Using the Disk Drive earlier in this section Bring up the Display menu 1 28 een GETTING STARTED EN 12 Press Format Press Marker Width twice to choose Spot Marker Press ACTIVE TRACE Press Marker Width twice to choose Spot Marker Press MARKER MODE Press Linked Markers Press MAX MIN Press SOURCE Press Configure Source Press Level Press 2 0 dBV Press MEAS Press Calculator Menu Press Argument Type twice to select Other Graph Press Operation three times to select divide Press Do Calc Choose the Up Dn dual trace format The reference graph will be the upper trace TraceO and the live graph will be the lower trace Trace1 Make the marker on the upper graph a spot marker Let s make the live graph the active trace Make the marker on the lower graph a spot marker Display the Marker Mode menu Link the two markers together Now when the knob moves one marker they both move together Since they are both spot markers the frequencies which they read on both graphs are identical Move the markers to the signal peak 1 kHz Bring up the Source menu Display the Sine frequency and level menu Select the Sine output level Enter 20 dBV The reference amplitude may be read from the marker readout of the upper graph The live amplitude may be read from the marker of the lower graph
304. ve trace as the argument There is no attempt to check whether the spans are the same or even whether the measurement data are of the same type In this case calculations are performed on a bin by bin basis i e bin 1 of one trace is added to bin 1 of the other trace bin 2 is added to bin 2 etc In the case of divide the active trace is divided by the inactive trace A disk file may be used as one of the traces by recalling a file into one of the graphs If the Argument type is a constant then the Argument and Marker to Argument functions are displayed Pressing the Argument key activates the constant argument entry field Use the keypad to enter a numerical argument Integer 3 real 3 0 or floating point 0 3E 1 formats are all allowed The Marker to Argument will copy the data value of the marker to the constant argument field above This is convenient when subtracting a baseline or normalizing to a data point Note This function takes the literal marker readout as shown above the graph and copies it to the argument field This is true even if the marker is reading in dBV rather than Volts The calculation will use the argument as if it were Volts and result in meaningless data Use linear units when using the Marker to Arg function to avoid this mistake The Return key will return to the main MEAS menu 4 14 nen MEASURE MENU EN 4 15 DISPLAY MENU M Display Format Up Dn Marker On
305. w is the one used to calculate the recalled graph not the window used for live calculations The File Type refers to the source of the data being displayed Live means that the data is real time Calculated data is the result of Trace Math and a filename is data recalled from a disk file At the upper right the measurement and display type and trace number 0 or 1 are shown The measurement type can be Spectrum PSD power spectral density Time record or Octave analysis The display types are Log Magnitude Linear Magnitude linear Real part linear Imaginary part and Phase On the active trace the measurement type and trace number are highlighted in inverse OPERATION MARKER DISPLAY The Marker Region is the graph region between the two heavy vertical dashed lines The marker region may be set to 1 division wide 1 2 division norm or a single vertical line spot The marker region does not change with horizontal scaling The Marker is a small square which seeks the minimum maximum or mean of the data within the marker region When seeking min or max the marker is located at the position of the data point which is the min or max This allows peaks and valleys in the data to be easily read out When seeking the mean the X position of the marker is at the center of the marker region and the Y position is the mean of the data within the region When a spot marker region is used the marker is confined to a
306. width and window function are compensated for in this calculation This allows measurements taken with different spans or windows to be compared Note PSD measurements are typically used to measure noise or noise density The data values are read out or dBV 1Hz When measuring Gaussian noise sources the noise in bandwidths other than 1 Hz may be obtained by multiplying the reading by the square root of the desired bandwidth This is true only for Gaussian noise When measuring PSD the Display may only be set to Log Magnitude or Linear Magnitude 4 4 nen MEASURE MENU EN Time Record Octave Analysis The Time Record is the minimum amount of filtered input data required to generate an FFT with the desired span and linewidth The SR770 filters the input data in real time to provide a stream of data points with the correct frequency span The time record consists of 512 of these points of which only the first 400 are displayed When averaging is on only spectra are averaged The Time Record shows the latest time record used to calculate a spectrum Note The SR770 is not a digital oscilloscope The Time Record always shows filtered data and does not resemble an oscilloscope trace of the same input The input data filter is a complex filter yielding complex outputs Thus the time record has a real and imaginary part as well as phase associated with each time bin Octave Analysis computes the spectral a
307. y window Use the ALT key to access the alphabetic keypad 4 65 SYSTEM MENU Subtitle Setup Plotter Menu Plot Abort SYSTEM This function activates the Subtitle entry field for alphanumeric entry The subtitle is added to the bottom of each plot below the title The subtitle may be up to 40 characters long The knob scrolls the subtitle within the entry window Use the ALT key to access the alphabetic keypad This key displays the Setup Plotter submenu described on the following pages Use this menu to configure the plotter interface and pen selections When plotting is in progress this function switches to Plot Abort Pressing this key aborts the plot Use the SYSTEM menu key to return to the main System menu 4 66 en SYSTEM MENU EHI Setup Plotter The Setup Plotter sub menu configures the SR770 plotter driver Interface plot speed and pen definitions are set in this submenu Plot Mode SYSTEM RS232 GPIB Baud Rate Plotter 9600 bd TT Plot Mode Tem RS232 GPIB ast Slow Define Plotter Address Pens Plot Speed Trace Pen Return Grid Pen Alpha Pen Marker Pen Return Plot Mode The SR770 can drive either an RS232 or GPIB interface plotter The plotter must be HP GL compatible This function selects which interface to use The plotter connects to the RS232 or GPIB connector on the rear panel Baud Rate Baud Rate If the Plot Mode is RS232 then the
308. ys to be printed to Epson compatible printers Output data is buffered by U703 an LS octal latch Output control bits are buffered by the open collector driver 0704 and input control bits are discriminated by U705C and U705D VIDEO GRAPHICS INTERFACE The video graphics interface is centered around U810 an HD63484 graphics controller The HD63484 generates the video sync_ signals controls the video memory and draws graphic primitives such as lines circles polygons etc and other high level functions The HD63484 relieves the 80C186 from having to calculate each video image and greatly increases display speed U813 and U814 are 32kbyte RAMs which make up the 64k video memory The video screen is 640H by 480V and requires 38 400 bytes of memory The remaining memory is used to store patterns fonts and other graphic objects The data and address are multiplexed and U811 and U182 are the address latches Data is read 16 bits at a time When data is required for the display the 16 bits of data are latched into U804 and U809 which are parallel to serial converters The video data is then shifted out at 13 5 MHz and synchronized by 08068 U803C blanks the video data except during active display times 7 3 Memory is accessed twice during each display cycle The first access reads the 16 bits of video data for the current display cycle The second access is used by the controller for drawing purposes During the drawing access d
309. ysis is on then entering this submenu not only activates the data table display it also enters the harmonic or sideband locations into the table Data tables are saved along with the trace data when data is saved to disk Data Tables are not stored in non volatile memory and are not retained when the power is turned off Save data to disk to preserve the data tables 4 37 ANALYZE MENU Table Index X Value Insert Item 12 5 kHz Y 13 21 dbV LogMag Spec 0 Table Index X Value 0 kHz 50 kHz Insert 20 dbV 20 dB div BMH File Live Item Delete Item Delete Table Return A sample data table display is shown above The table entries are n table index or line number X user defined X values and Y measured data values corresponding to the X values The Y value is actually for the frequency bin which is closest to the entered X value within one bin resolution The Y values shown in the table are in the units of the display X values which are not in the frequency span have the message OVRG for their Y values This key activates the Table Index entry field Knob adjustment and numeric entry are both permitted When using the knob scrolling past the last index will add a new line If an index greater than the last index is entered then a new line is added after the end of the table If the table is longer than what can be displayed in the window then
310. z 1 kHz 65536 0 1 Vpk to 1 Vpk 0 to 10 kHz 80 dBc 10 kHz to 100 kHz lt 70 dBc 100 dBV typical line frequency related 1 0 09 dB of setting O Hz to 100 kHz 0 1 Vpk to 0 5 Vpk high impedance load 15 26 mHz 1 kHz 65536 0 1 Vpk to 0 5 Vpk 0 to 10 kHz 80 dB below larger tone 10 kHz to 100 kHz lt 70 dB below larger tone 100 typical line frequency related Output is 0 Hz to 100 kHz at all measurement spans 0 25 dB pk pk typical 1 0 dB pk pk max 5000 rms averaged spectra Source Cal on Output is 0 Hz to 100 kHz at all measurement spans 4 0 dB pk pk 20 Hz 20 kHz measured using 1 3 octave analysis Source Cal on Output is equal amplitude sine waves at each frequency bin of the measurement span Measured spectra all spans Source Cal on 0 05 dB pk pk typical 0 2 dB pk pk max Amplitude 1 0 Vpk Auto Phase function calibrates to current phase spectrum Monochrome CRT 640H by 480V resolution Adjustable brightness and screen position vi 770 FFT SPECTRUM ANALYZER EN Interfaces Hardcopy Disk Power Dimensions Weight Warranty IEEE 488 RS232 and Printer interfaces standard All instrument functions can be controlled through the IEEE 488 and RS232 interfaces A PC keyboard input is provided for additional flexibility Screen dumps and table and setting listings to dot matrix and HP LaserJet compatible printers Data plots to HP GL compat

SR770 Manual - Stanford Research Systems

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