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Timer/Counter/ Analyzer

1. 5ns Fig 5 9 Synchronization using start arm ing Do the following steps to perform synchroni zation using start arming Connect SYNC to input E Connect the burst signal to input A Adjust the trigger level to match the burst signal under study Press SETTINGS Arm Select Start Arm Delay 0 and Start Chan E Use MEAS FUNC to select Pulse Width A If there is no or too little time difference be tween the arming signal and the first pulse in the pulse burst arming must be combined with a delay See example C m C Synchronization Using Start Arming With Time Delay If the pulse bursts have a stable repetition fre quency you synchronize the measurement us ing Start Arming with Time Delay Here you use the SYNC pulse belonging to a preceding burst to synchronize the start of measurement Measurement Control Set the time delay to a time longer than the duration of a pulse burst and shorter than the repetition time of the pulse bursts See Fig 5 10 Sync E Delay Input A Fig 5 10 Synchronization using start arming with time delay Use the same test setup as in the preceding ex ample but enter a suitable Start Arm Delay 2 Measuring the Second Burst Pulse The next task is to measure the width of the second pulse in the pulse train from example 1 How can we now synchronize the measure ment start to the start of the
2. 4 9 Arming Examples 00 5 9 Reciprocal Counting 4 9 Introduction to Arming Examples 5 9 Sample Hold 4 10 1 Measuring the First Burst Pulse 5 9 Time Out 0 2 eee eee 4 10 2 Measuring the Second Burst Pulse5 11 Measuring Speed 4 10 3 Measuring the Time Between PERIOD saraga ieaiai damia 4 12 Burst Pulse 1 and 4 5 12 Single Ar Baoi aE 4 12 4 Profiling ecceri siae 5 13 Average A B C 20 5 4 12 Time Measurements 4 13 6 Process Introduction 00 cece eeees 4 13 Introduction 0 eee 6 2 Triggering E 4 13 Averaging 1 2 22 eee eee 6 2 Time Interval 22222 0 4 14 Mathematics 00 6 2 Time Interval AtoB 4 14 Example 6 2 Time IntervalBtoA 4 14 Statistics aoea oaa e ea id 6 3 Time IntervalAtoA BtoB 4 14 Allan Deviation vs Standard Deviation 6 3 Rise Fall Time A B 4 14 Selecting Sampling Parameters 6 3 Pulse Width A B gt oaaao 4 15 Measuring Speed s inr er 84 Determining Long or Short Time Duty Factor A B 4 15 Instability lcs 6 4 Measurement Errors 4 15 Statistics and Mathematics 6 5 Hysteresis 0 005 4 15 Confidence Limits 6 5 Overdrive and Pulse Rounding 4 16 Jitter Measurements 6 5
3. l l 8 11 PASC x mine u sna R 8 11 Duty Factor ovrog entes 8 11 Galibration ses eee ee eter eth 8 12 Definition of Terms 8 12 General Specifications 8 12 Environmental Data 8 12 Power Requirements 8 12 Dimensions amp Weight 8 13 Ordering Information 8 13 Timebase Options 8 14 Explanations 2 2 Red 8 14 9 Index 10 Service Sales and Service office 10 2 GENERAL INFORMATION About this Manual This manual contains directions for use that apply to the Timer Counter Analyzer PM6690 In order to simplify the references the PM6690 is further referred to throughout this manual as the 90 Warranty The Warranty Statement is part of the Getting Started Manual that is included with the shipment Declaration of Conformity The complete text with formal statements concerning product identification manufacturer and standards used for type testing is available on request VI Chapter 1 Preparation for Use Preparation for Use Preface Introduction Congratulations on your choice of instrument It will serve you well for many years to come Your Timer Counter Analyzer is designed to bring you a new dimension to bench top and system counting It offers significantly in creased performance compared to traditional Timer Counters The PM6690 offers the fol lowing advantages 12 digits of freq
4. Prescaling Factor Input 2 A amp B 16 C 3 GHz 256 C 8 GHz Specifications Phase Wm Typical Random Uncertainty rms NOTE Phase is an auxiliary measurement function intended to give an indication with no guaranteed specification U ma Jd Strt Trg Err Stop Trg Err X xFreq x360 m Systematic Uncertainty Uss LE 500ps x Freq x 360 7 Duty Factor m Random Uncertainty rms Oma T Strt Trg Err Stop Trg Err x Freq or minimum ppm m Systematic Uncertainty Usu 4 EP Q00 ps x Freq dimensionless e g ppm Measurement Uncertainties 8 11 Specifications Calibration Mode Closed case menu con trolled Calibration Input A Password Protection ON or OFF Input Frequen cies used for TB Calibration 1 0 1 544 2 048 5 0 or 10 0 MHz Definition of Terms Calibration Ad justment Toler ance The maximum tolerated deviation from the true 10 MHz frequency after calibration If the timebase frequency does not ex ceed the tolerance limits at the moment of calibra tion an adjustment is not necessary Total Uncertainty The total possible devia tion from the true 10 MHz frequency under influence of frequency drift due to aging and ambient tem perature variations versus the reference tempera ture The operating tem perature range and the calibration interval are part of this specificati
5. Fig 1 4 Fitting the rack mount brackets on the counter Preparation for Use WARNING Do not perform any inter nal service or adjustment of this instrument unless you are qualified to do so Before you remove the cover dis connect mains cord and wait for one minute Capacitors inside the instrument can hold their charge even if the in strument has been separated from all voltage sources m Assembling the Rackmount Kit Make sure the power cord is disconnected from the instrument Turn the instrument upside down See Fig 1 5 Undo the two screws A and remove them from the cover Remove the rear feet by undoing the two screws B Remove the four decorative plugs C that cover the screw holes on the right and left side of the front panel Grip the front panel and gently push at the rear Pull the instrument out of the cover 16 10 af Remove the screws and push the counter out of the cover Fig 1 5 Unpacking 1 9 Preparation for Use Remove the four feet from the cover Use a screwdriver as shown in the following illustration or a pair of pliers to remove the springs holding each foot then push out the feet V Fig 1 6 Removing feet from the cover Push the instrument back into the cover See Fig 1 5 Mount the two rear feet with the screws B to th
6. 0 2 V max i V min ually adjust the relative trigger levels in when Auto Trigger is active Both input channel menus are used for entering the lev els but only one channel is the active signal input See the paragraph on Auto Trigger page 4 16 to find out how overshoot or ringing may af fect your measurement Pulse Width A B The function menu designation is Pulse Ei ther input A or input B can be used for mea suring and both positive and negative pulse width can be selected Positive pulse width means the time be tween a rising edge and the next falling edge Negative pulse width means the time be tween a falling edge and the next rising edge The selected trigger slope is the start trigger slope The counter automatically selects the inverse polarity as stop slope Duty Factor A B The function menu designation is Duty Ei ther input A or input B can be used for mea suring and both positive and negative duty factor can be selected See the preceding para graph for a definition of positive and negative in this context Duty factor or duty cycle is the ratio be tween pulse width and period time The coun ter determines this ratio by first making a pulse width measurement then a period mea surement and calculates the duty factor as Measuring Functions Pulse width Duty factor f Period The total measurement time will be doubled compared to a single measurement becaus
7. You can set two levels by entering the submenus named Lower Limit resp Upper Limit Any numerical value can be entered us ing scientific notation The active keys are the digits 0 9 the decimal point the change sign and the softkey designated EE for toggling between the mantissa and the exponent Typos are erased by pressing the left arrow key Confirm by pressing ENTER Limit Behavior Press Limit Behavior to set how the counter will react on limit crossings The following choices exist Off No action taken LIM indicator is OFF 6 6 Limits In all other behavior modes the LIM in dicator is ON and non flashing unless the limits set in the Limit Mode menu have been crossed Capture The measurements are compared with the limits set under Lower Limit and Upper Limit and the LIM symbol will be flashing when the active Limit Mode has set the LIM flag Only samples meeting the test criterion will be part of the population in statistics presentations Alarm The measurements are compared with the limits set under Lower Limit and Upper Limit and the LIM symbol will be flashing when the active Limit Mode has set the LIM flag All samples i e also those outside the limits will be part of the population in statistics presentations Alarm stop The measurements are compared with the limits set under Lower Limit and Upper Limit and the LIM symbol will be flashing when the active Limit Mode h
8. function 0 0 0 4 4 Reciprocal counting 4 9 Reference Oscillators CHECKING dic xau oe prios 7 8 Restart loa RES 5 2 RF input checking 7 11 Rise Falltime 4 14 S Sample Hold 4 10 Sensitivity 04 4 15 Checking 7 5 Setup time Tor aiming eee aces are suas 5 9 SNIE i ace PPM DIE 4 10 Single shot phenomena 5 6 Smart Frequency 2 11 Smart Time Interval 2 11 Speed ariming se Gaede hae ee eels 5 9 of measurement 4 10 Standard deviation 6 3 Start arming 25 5 2 5 6 of ameasurement 5 4 StatiSti S eo ven aad ee ener 6 3 and Mathematics together 6 5 Stop Aid cs vo leave aoa aS 5 2 5 6 of measurement 5 5 Synchronization of ameasurement 4 11 Syncronization delay arming xs tene Het ed s 5 7 Systematic errors in Phase measurements 4 19 T Time period 24e Rs 4 12 to set up arming 5 9 TIG QUE Eh ERR ia 2 11 AUO santos dad ein EI Speak Res 4 10 fixed sie ddbdwisidedebe bade 4 10 manual cres RR EAE 4 10 Touch hold See Sample hold Transient profiling 5 14 Trigger error eases ret 3 8 Trigger Hold Off 3 4 Trigger hysteresis 3 6 Trigger Indicators Checking e kd 7 7 Trigger level AUTO iie i eee ee e
9. 7 eLuKE PM6690 FREQUENCY COUNTER TIIM S ANALYZER 100ps 300M z VALUE sw IL C3 mua J E Je e TRIG B Rm c C L 0 3 8GHz 50n MAX 30dBm S 6 7 8 9 0 5 INPUT A INPUT B sers veru im luser OPT hororu L RESRART S 12Vrms 500 30Vrms IMN HOLD RUN Toggles between HOLD one shot mode and RUN continuous mode Freezes the result after completion of a measurement if HOLD is active RESTART Initiates one new measure ment if HOLD is active CANCEL Moves up one menu level with out confirming selections made EXIT OK Confirms menu selections and moves up one level in the menu tree Exits REMOTE mode if not LOCAL LOCKOUT ENTER Confirms menu selections with out leaving the menu level Basic Controls 2 3 Using the Controls Secondary Controls Connectors amp Indicators GRAPHIC DISPLAY 320 x 97 pixels LCD with backlight for show ing measurement results in numerical as well as graphical format The display is also the center of the dynamic user interface compris ing menu trees indicators and information boxes SOFTKEYS The function of these seven keys is menu de pendent Actual function is indicated on the LCD Depressing a softkey is often a faster alterna tive to moving the cursor to the desired posi tion and then pres
10. Auto Trigger 4 4 16 Mnyaa extende As 6 6 Phase csse eE eere 4 17 Limit Behavior 6 6 What IS Phase n n uana 4 17 muie rr eenehalieheh taki nae Ber R sol tiolrz v Mese o lr we ae 4 17 Limits and Graphics 6 7 Possible Errors oret 4 18 INACCURACIES 1a eee tt 4 18 T Performance Check Voltage nnn 7 A Sle eat ee ae a ds Mus Mam Mage tuuc ie ut ue os 4 22 Preparations n 7 2 Test Equipment 7 2 uns ere area r a TT OTT 4 23 Front Panel Controls 7 3 5 Measurement Control Internal Self Tests 7 3 3 Keyboard Test 7 3 About This Chapter 5 2 nj Measurement Time 5 2 Short Form Specification Test seems 7 5 Gate Indicator 5 2 Sensitivity and Frequency Range 7 5 Single Measurements 5 2 M pooner etinene ee pies is P9 IV Trigger Indicators vs Trigger Levels 7 7 Input Controls 7 8 Reference Oscillators 7 8 Resolution Test 7 9 Rear Inputs Outputs 7 9 10 MHz OUT encenta RR 7 9 EXT REF FREQ INPUT 7 9 EXT ARM INPUT ssesssse 7 9 Measuring Functions 7 10 Check of HOLD OFF Function 7 10 OpllONS 1 2 2e Lota bonne hed awe es 7 11 Input C Check 7 11 8 Specifications IntrodUctlOn x eo antes ede Gu
11. Compatible The SCPI command set used in this mode is adapted to be compatible with Agilent 53131 132 181 GPIB Address Value input menu for setting the GPIB ad dress Test A general self test is always performed every time you power up the instrument but you can order a specific test from this menu at any time Frequency fi EAE 4 194 669 437 mz User options Test Test mode Start ALL test Fig 2 28 Self test menu Press Test Mode to open the menu with available choices Frequency fi EAE 4 194 669 038 mz User options Test Testmode BI RaM ROM Logic Display Interface Fig 2 29 Selecting a specific test Select one of them and press Start Test to run it 2 14 Description of Keys Blank Digits Jittery measurement results can be made eas ler for an operator to read by masking one or more of the LSDs on the display Place the cursor at the submenu Digits Blank and increment decrement the number by means of the UP DOWN arrow keys or press the soft key beneath the submenu and enter the desired number between 0 and 13 from the keyboard The blanked digits will be repre sented by dashes on the display The default value for the number of blanked digits is 0 About Here you can find information on calibration date firmware versions for basic instrument interfaces e optional factory installed hardware m Hold Run This key serves the purpose o
12. Input Frequency 0 1 Hz 200 MHz Min Pulse Width 2 5 ns Modes Pos or neg duty factor m Display Main Parameter Duty factor Aux Parameters Period pulse width 8 4 Measurement Functions V max Vmin Vp p A B Alternative data within parentheses refer to in put attenuator setting x10 Range 5 V to 5 V 50 V to 50 V Input Frequency DC 1Hz 300 MHz 100 Hz 300 MHz default higher LF limit means higher meas speed Mode Vmax Vmin Vp p Resolution 3 30 mV Accuracy typ DC 1 15 150 mV 1 Hz 1 kHz 1 15 150 mV 1 kHz 20 MHz 3 15 150 mV 20 100 MHz 10 15 150 mV 100 300 MHz 30 15 150 mV Vp p is calculated as Vmax Vmin which means that the maximum absolute error will be 30 300 mV m Display Main Parameter Vmax or Vmin or Vp p Aux Parameters Vmin Vp p Or Vmax Vp p or Vmin Vmax Specifications Timestamping A B C This function is only accessible via GPIB or USB No absolute time exists timestamp values can only be used for relative time measurements Timestamps are taken of two consecutive pos itive edges and two consecutive negative edges pos neg pos neg or neg pos neg pos and the number of positive edges is counted Max Frequency 160 MHz Min Pulse Width 2 5 ns Timestamp Reso lution 70 ps rms Max Frequency to catch each edge 250 kHz Auto Set Manual Set All measuring functions can be auto set using best
13. ORI 8 Vp x 2n x FREQ And the corresponding phase error in degrees is 10mV x 360 x FREQ Vp x 2n x FREQ which can be reduced to 06 y This error can occur on both inputs so the Worst case systematic error is thus 0 6 06 C Ve A V B Vpeak Vpeak Worst case A B systematic error 150 mV 150mV 4 4 8 1 5V 150mV 0 4 4 4 4 1 5 V 1 5V 0 4 0 4 0 8 Table 4 3 Systematic trigger level timing error examples m Methods of Compensation The calculations above show the typical un certainties in the constituents that make up the total systematic error For a given set of input signals you can compensate for this error more or less completely by making calibration measurements Depending on the acceptable residual error you can use one of the methods 4 20 Possible Errors described below The first one is very simple but does not take the inter channel propaga tion delay difference into account The second one includes all systematic errors if it is car ried out meticulously but it is often not practi cable Common settings for the two inputs are Slope Pos or Neg Coupling AC Impedance 1 MQ or 50 Q depending on source and frequency Trigger Man Trigger Level OV Filter Off Method 1 Connect the test signals to Input A and Input B Select the function Phase A rel A to find the initial error Use the MA
14. STANDBY INPUT A Input A Menu for setting e Coupling Impedance etc Man Trig Trig xy mV Menu for entering numeric values in V or mV 0 123V Trig 0 123 V 5 times Trig V 4 567 Trig 4 567 V lt 5 times Trig V 8 9 Trig 8 9 V t Trig 8 9 V mV Trig 8 9 mV V Trig 8 9 V AUTOSET Menu disappears INPUT B Input B Menu for setting Pe Coupling Impedance etc SETTINGS Settings Menu for setting Meas Time Hold Off Ref Source etc ENTER Meas Time 200 ms A Meas Time 500 ms v Meas Time 200 ms EXIT OK Settings Menu for setting Meas Time Hold Off Ref Source etc EXIT OK Menu disappears MATH LIM Math Limit Menu for selecting post processing formula and alarm limit USER OPT User options Menu for Calibration Memory Management In terface etc CANCEL Menu disappears HOLD RUN Hold At upper right corner HOLD RUN Hold disappears MEAS FUNC Measure function Menu for selecting measurement function 7 4 Front Panel Controls Performance Check Key s Display Notes P F gt Period Cursor position marked by text inversion ENTER Single A EXIT OK Menu disappears Period Single A at upper left corner STAT PLOT Period Single A Aux parameters Max Min P P Adev Std MEAN VALUE Stat parameters dis appear Table 7 2 Keyboard test Short Form Specification Test Sensitivity and Frequency Range Recall the DEFAULT settings Press INPUT A S
15. 001 0 MHz 100 10 000 041 617 9 wz H 1536 of 2000000000 0 Max 10 000 041 96 MHz P P 0 79 Hz Min 10 000 041 17 MHz fidev 0 12 Hz Std 0 12 Hz 4 999 999 999 0 MHz 0 05 Ms Fig 2 4 Statistics presented numerically In this mode the statistical information is dis played as numerical data containing the fol lowing elements Mean mean value e Max maximum value Min minimum value P P peak to peak deviation e Adev Allan deviation Std Standard deviation Histogram Frequencu fi MEAS 100 mHz div 10 000 041 2 MHz 0 Fig 2 5 Statistics presented as a histo gram The bins in the histogram are always autoscaled based on the measured data Lim its if enabled and center of graph are shown as vertical dotted lines Data outside the limits are not used for autoscaling but are replaced by an arrow indicating the direction where non displayed values have been recorded 2 8 Description of Keys Fig 2 6 Running trend plot This mode is used for observing periodic fluc tuations or possible trends Each plot termi nates if HOLD is activated or restarts if RUN is activated after the set number of samples The trend plot is always autoscaled based on the measured data starting with 0 at restart Limits are shown as horizontal lines if enabled m Remote When the instrument is controlled from the GPIB bus and the remote line is asserted the presentation mo
16. PM9627H Timer Counter including standard timebase and GPIB interface 12 months product war ranty line cord brochure with important information getting started manual printed operators amp pro gramming manuals on CD Certificate of Calibra tion 3 GHz Input C 8 GHz Input C Very high stability OCXO Ultrahigh stability OCXO Modulation domain analy sis SW Rear panel inputs Rackmount kit Carrying case Heavy duty hard transport case Ordering Information 8 13 Specifications Timebase Options Product Family 90 Option Standard PM6690 5 PM6690 6 Timebase Type UCXO OCXO OCXO Uncertainty due to Calibration adjustment tolerance 6 8 9 23 C 3 C 1x10 1x10 3x10 Aging per 24 h 1 z lt 6x10 7 2 lt 3x1 0 per month lt 5x10 lt 1x10 lt 3x10 per year lt 5x10 lt 5x10 1 5x10 Temperature variation 0 C 50 C 1x07 5x10 2 5107 20 C 26 C typ values 3x10 1x10 4x10 Power voltage variation 1096 1x10 5x10 10 5x10 10 Short term stability Root Allan Variance v 21s not specified 1x10 1 5x10 12 Typical values x 10 s 1x10 5x101 Power on stability 1 E P Deviation versus final value after 24 h 1x10 5x10 on time after a warm up time of 30 min 10 min 10 min Total uncertainty for operating temperature 0 C to 50 C 26 95 confidence interval 5 8 8 1 year after calibration 1 2x1 LR 6x1
17. Test Ifa fault is detected an error message ap pears on the display and the program halts Note any error messages If no faults are detected the instrument re turns to the normal measurement mode Keyboard Test This test verifies that the timer counter re sponds when you press any key It is nota functional test Such tests are performed later in this chapter The important thing here is Performance Check that something changes on the display when you press a key Consequently you can press the keys in almost any order without paying attention to the exact response but for those who want to be more systematic there is a ta ble overleaf where all keys are exercised at least once Press the keys as described in the first column and look at the display for the text in the sec ond column Some keys change more text on the display than described here The display text mentioned here is the one mostly associ ated with the selected key NOTE For the instrument to respond correctly this test must be carried out in se quence and you must start with the DEFAULT setting See page 2 13 No signals should be applied to the input connectors Front Panel Controls 7 3 Performance Check Key s Display Notes P F STANDBY Off Red standby LED On Key common to ON ON Backlight On Red standby LED Off Key common to
18. UP cursor key and note the results If Trigger Hold Off time 100 ns the result is about 100 ns i e the same value as without Hold Off If Trigger Hold Off time 7100 ns the result is about 100 ns Trig Hold Off time Connect the signal to Input B select Period Single B and repeat the tests above Options Input C Check To verify the specification of the different RF prescalers Input C use the following basic Performance Check Connect the output of a signal generator covering the specified frequency range to the RF input of the counter Connect the 10 MHz REF OUT from the generator to the EXT REF IN on the rear panel of the counter test setup Selected Function Action Display P F FREQA 10 MHz FREQ B 10 MHz FREQ C 500 MHz 15 dBm to Inp C 500 MHz FREQ RATIO A B 1 FREQ RATIO C B 50 29 PER SINGLE A 100 ns PER SINGLE B 100 ns PER AVERAGE A 100 ns PER AVERAGE B 100 ns TIME INT A to B POS SLOPE A NEG SLOPE B 50 ns NEG SLOPE A POS SLOPE B 50 ns PULSE POSA 50 ns PULSE NEG A 50 ns RISE TIME A 30 ns FALL TIME A 30 ns PHASE A rel B POS SLOPE A NEG SLOPE B 180 or 180 PHASE B rel A 180 or 180 PHASE A rel A POS SLOPE A POS SLOPE B 0 or 360 DUTY POS A 0 5 DUTY NEG A 0 5 VOLT MAX A 0 75 V VOLT MIN A 0 75 v Table 7 7 Measuring functions check 1
19. Value depends on the symmetry of the signal 2 Exact value depends on input signal 3 If an RF option is installed Options 7 11 Performance Check Choose Meas Ref from the SETTINGS menu and select External Choose Freq C from the MEAS FUNC menu Generate a sine wave in accordance with the tables Verify that the counter is counting cor rectly The last digits will be unstable Frequency Amplitude P F MHz mVrus dBm 100 300 20 21 300 2500 10 27 2500 2700 20 21 2700 3000 40 15 Table 7 8 RF input sensitivity 3 GHz Option Frequency Amplitude P F MHz mVrus dBm 300 500 20 21 500 3000 10 27 3000 4500 20 21 4500 6000 40 15 6000 8000 80 9 Table 7 9 RF input sensitivity 8 GHz Option 7 12 Options Chapter 8 Specifications Specifications Introduction Only values with tolerances or limits are guar anteed data Values without tolerances are in formative data without guarantee Measurement Functions Refer to page 8 10 for uncertainty informa tion Inputs A and B can be swapped in all modes except Rise Time and Fall Time Display All measurements are displayed with a large main parameter value and smaller aux iliary parameter values with less resolution Some measurements are only available as aux iliary parameters Frequency A B C m Range Input A 0 002
20. and the time can be set within the range 2 us 1000 s Timebase Reference Frequency fi neas 4 194 664 464 mz Settings TimebaseRef Int Ext fiuto Fig 2 15 Selecting timebase reference Source Here you can decide if the counter is to use an Internal or an External timebase A third al ternative is Auto Then the external timebase will be selected if a valid signal is present at the reference input The EXT REF indicator at the upper right corner of the display shows that the instrument is using an external timebase reference Miscellaneous Frequency fi maas 98 121 211 843 knz Settings Misc Smart Time Smart futo Trig Interval Freq Low Freq Timeout Off Auto 100 Hz toff Fig 2 16 The Misc submenu The options in this menu are Smart Time Interval valid only if the se lected measurement function is Time In terval The counter decides by means of timestamping which measurement channel precedes the other Smart Frequency valid only if the se lected measurement function is Fre quency or Period Average By means of continuous timestamping and regression analysis the resolution is increased for measuring times be tween 0 2 s and 100 s Auto Trig Low Freq In a value input menu you can set the lower frequency limit for automatic trig gering and voltage measurements within the range 1 Hz 100 kHz A higher limit means faster settling time and conseq
21. arming pulse similar to a delayed timebase in an oscilloscope You can choose to delay start arming by a pre set time Start arming can be used for all functions ex cept Frequency Burst Ratio and Volt If you use start arming to arm an average mea surement it only controls the start of the first sample Stop Arming Stop arming prevents the stop of a measure ment until the counter detects a level shift on the arming input Combining Start and Stop Arming results in an external gate function which determines the duration of the measure ment Stop arming can be used for all functions ex cept Frequency Burst Ratio Volt and Rise Fall Time About This Chapter 5 3 Measurement Control Controlling Measurement Timing The Measurement Process Basic Free running Measurements Since these counters use the reciprocal count ing technique they always synchronize the start and stop of the actual measuring period to the input signal trigger events A new mea surement automatically starts when the previ ous measurement is finished unless HOLD is on This is ideal for continuous wave signals The start of a measurement takes place when the following conditions have been met in or der The counter has fully processed the previ ous Measurement All preparations for a new measurement are made The input signal triggers the counter s measuring input The measurement ends when t
22. depth Up to 85 depth Min signal must exceed min oper input voltage 50 Q nom AC coupled VSWR lt 2 511 7 Vrms PIN diode protected Type N female Rear Panel Inputs amp Outputs Ref Input Ref Output Arming Input E Freq Range Trigger Level Trigger Slope 1 5 or 10 MHz 0 1 5 Vrms sinewave impedance gt 1 kQ 1x10 MHz gt 1 Vrms into 50 Q load Arming of all meas func DC 80 MHz TTL 1 4 V nom Positive or negative Meas Inputs Impedance Connectors A B C option 1 MQ 50 pF or 50 Q VSWR x 2 1 BNC SMA for Input C Auxiliary Functions Trigger Hold Off Time Delay Range 20 ns 2 s 10 ns resol External Start Stop Arming Modes Input Channels Max Rep Rate for Arming Signal Channel A B Channel E Start Time Delay Range Start arming stop arming start and stop arming A B E EXT ARM 160 MHz 80 MHz 10 ns 2 s 10 ns resol NOTE Stop arming has no delay setting Statistics Functions Display Graphic Sample Size Maximum minimum mean Amax min Standard deviation Allan deviation Numeric or numeric graphic Histogram amp trend plot auto scaled 2 to 2 x 10 Max Sample Rate Limit Qualifier Meas Pacing Specifications 250 kSa s measured 2 kSa s calculated depending on meas func tion and graphics Off Capture amp store values above limit 2 Capture amp store values b
23. digital time measurement and the analog interpolation measurements The result is that the basic digital resolution of 1 clock pulse 10 ns is reduced to 100 ps for the 90 Since the measurement is synchronized with the input signal the resolution for frequency measurements is very high and independent of frequency The counters have 14 display digits to ensure that the display itself does not restrict the res olution Remote Control This instrument is programmable via two in terfaces GPIB and USB The GPIB interface offers full general func tionality and compliance with the latest stan dards in use the IEEE 488 2 1987 for HW and the SCPI 1999 for SW In addition to this native mode of operation there is also a second mode that emulates the Agilent 53131 132 command set for easy ex change of instruments in operational ATE systems The USB interface is mainly intended for the lab environment in conjunction with the op tional TimeView M analysis software The communication protocol is a proprietary ver sion of SCPI 1 4 Preface Fast GPIB Bus These counters are not only extremely power ful and versatile bench top instruments they also feature extraordinary bus properties The bus transfer rate is up to 2000 triggered measurements s Array measurements to the internal memory can reach 250 k measure ments s This very high measurement rate makes new measurements possible For example you c
24. displayed 1 KeX L 2 KIX L 3 K X L M 4 K X L M 5 XIM 1 Press MATH LIM Math to enter the first mathematics submenu See page 2 12 how to 6 2 Introduction enter the constants K L and M and how to se lect the formula that best suits your need The default values of K L and M are chosen so that the measurement result is not affected directly after activating Math Recalling the default setting will restore these values as well Example If you want to observe the deviation from a certain initial frequency instead of the abso lute frequency itself you can do like this Recall the default settings by pressing USER OPT Save Recall Recall Setup Default Connect the signal to be measured to input A Press AUTO SET to let the counter find the optimum trigger conditions on its own Press MATH LIM Math L f the current display value is suitable for your purpose then press Xo It will then be transferred to the constant L You can repeat pressing Xo until you are satisfied The constant will be updated with the lat est measurement result Instead of using Xo you can enter any nu merical value from the front panel Let s assume that 10 MHz is your reference fre quency The mantissa is marked by text in version for immediate editing Press 1 gt 0 t EE 6 Confirm by pressing EXIT OK Now the constant L is updated and displayed as 10E6
25. fre quency the pulse repetition frequency PRF can be measured often without the support of an external arming signal 2 10 Description of Keys Arming is the general term used for the means to control the actual start stop of a measure ment The normal free running mode is inhib ited and triggering takes place when certain pretrigger conditions are fulfilled The signal or signals used for initiating the arming can be applied to three channels A B E and the start channel can be different from the stop channel All conditions can be set via the menu below Trigger Hold Off Frequency fi Meas 50 000 001 76 mz Settings Hold off Trigger Hold Off hold off E Off 200 us Fig 2 13 The trigger hold off submenu A value input menu is opened where you can set the delay during which the stop trigger conditions are ignored after the measurement start A typical use is to clean up signals gen erated by bouncing relay contacts Statistics Frequency in Burst A MEAS 4 194 663 8 mz Settings Stat Ho Of Ho Of Pacing Samples Bins Pacing Time 100 20 Off is Fig 2 14 Entering statistics parameters Using the Controls In this menu you can do the following Set the number of samples used for cal culation of various statistical measures Set the number of bins in the histogram view Pacing The delay between measurements called pacing can be set to ON or OFF
26. imer Counter nalyzer PM6690 Operators Manual FLLIKE PN 4822 872 20301 March 2007 Seventh Edition 2005 Fluke Corporation All rights reserved Printed in Sweden Il Table of Contents GENERAL INFORMATION About this Manual Warranty Declaration of Conformity 1 Preparation for Use Preface ev eden EX e wie ces Introduction 646 soos Ru Powerful and Versatile Functions No Mistakes 005 Design Innovations State of the Art Technology Gives Durable Use Safety Precautions Caution and Warning Statements Symbols osre nan Sec agen rives If in Doubt about Safety Unpacking lene qur p ms Identification Installations 3 er tnn Supply Voltage Grouriding oig edo 1 8 Orientation and Cooling Fold Down Support Rackmount Adapter 2 Using the Controls Basic Controls 2 04 Secondary Controls Connectors amp Indicators 1 2 1 3 1 8 1 9 1 4 1 4 1 5 Ill Rear Panel co oc eR rns 2 5 Description of Keys 2 6 POWER seem E mers 2 6 Select Function ce cae ee eta 2 6 Autoset Pr set coser ema 2 6 MoVe GUISOF nnne tns 2 6 Display Contrast 2 7 Enter isse ere me mmn 2 7 Save amp EXIU cse re Le 2 7 Don t Save amp Exit l lusu 2 7 Presentation Modes 2 7 Entering Numeric Values 2 8 Hard Menu Keys 2 9 D
27. measurement is further controlled by the fol lowing elements Manual RESTART if HOLD is selected GPIB triggering lt GET gt or TRG if bus triggering is selected External arming signal if Start Arming is selected Expired start arming delay if Arming Delay is selected In addition to expired measurement time and stop signal triggering the stop of measure ment is further controlled by External arming signal triggering if Stop Arming is selected GPIB triggering is described in the Program ming manual Now let s look deeper into the concept of arming What is Arming Arming is a pretrigger condition qualifier that must be fulfilled before the counter al lows a measurement to start Arming can also be used to qualify the stop of a measurement This is called stop arming The Measurement Process 5 5 Measurement Control as opposed to the more common start arm ing When you use arming you disable the normal free run mode i e individual measurements must be preceded by a valid start arming sig nal transition If you use start arming and stop arming to gether you get an externally controlled mea surement time a so called External Gate m Manual Arming The counters have a manual start arming func tion called HOLD Here you manually arm the start of each individual measurement by pressing the RESTART key Use this manual arming mode to measure
28. second pulse In this case auto synchronization without the use of the arming function cannot work Auto synchronization can be used only to syn chronize on the first trigger event in a burst Depending on the SYNC signal s position rel ative to the burst and the duration of the SYNC signal the measurement can be per formed with or without using arming delay Ifthe trailing edge of the SYNC signal occurs after the leading edge of the first pulse but be fore the second pulse in the pulse burst then normal start arming without delay can be used Select triggering on positive slope on in put A and negative slope on input E The slope for the active arming channel is set in the SETTINGS Arm Start Slope menu This example is shown in the following figure If the SYNC pulse timing is not so suitable as in the above measurement example then arm SyncE t Start Arming Input A Fig 5 11 If the trailing edge of the sync signal appears before the sec ond pulse use arming without delay ing must be used combined with a time delay see the following figure Sync E i L Start Arming Delay P i Ju gU Input A Fig 5 12 Use arming with delay if the trailing edge of the sync signal appears too late to be useful Use the same test setup as in the preceding ex ample but enter a suitable Start Arm Delay The set delay time must be set to expire in the gap between pulse 1 a
29. settings for the individual functions This means e g an auto hysteresis of 40 of Vp p in frequency measurements an auto trigger at 50 of Vp p with minimum hysteresis incl hysteresis compensation in time measure ments an auto find of burst length and auto sync for frequency burst measurements etc Input and Output Specifications Inputs A and B Alternative data within parentheses refer to in put attenuator setting x10 Frequency Range DC coupled DC 300 MHz AC coupled 10 Hz 300 MHz Coupling AC or DC Rise Time Approx 700 ps Impedance 1 MQ 25 pF or 50 Q VSWR 2 Trigger Slope Positive or negative Channels Separate A amp B common via A common via B Max Channel Timing Difference 500 ps Hysteresis Window Approx 30 300 mVp p Residual Hyster esis after Com pensation 5 50 mV DC 10 kHz Sensitivity DC 200 MHz 15 mVrms 200 300 MHz 25 MVrms Auto Trig 35 MVrms Attenuation x1 x10 Dynamic Range x1 30 mVp p to 10 Vp p within 5 V window Trigger Level Read out on display Resolution 3 30 mV Uncertainty 15 150 mV 1 of trigger level Auto Automatically set to 50 or 70 of input signal 10 and 90 for rise fall time Relative level in man ually adjustable when necessary Input and Output Specifications 8 5 Specifications Auto Hysteresis Time Meas Minimum hysteresis win dow compensation Freq Meas amp Per Avg 70 and 30
30. system atic trigger error includes this error but you can avoid it by having adequate overdrive Rounding Very fast pulses may suffer from pulse rounding overshoot or other aberrations Pulse rounding can cause significant trigger errors partic ularly when measuring on fast cir cuitry 4 16 Measurement Errors Auto Trigger Auto Trigger is a great help especially when you measure on unknown signals However overshoot and ringing may cause Auto to choose slightly wrong MIN and MAX signal levels This does not affect measurements like frequency but transition time measurements may be affected Therefore when working with known signals such as logic circuitry set the trigger levels manually Always use manual trigger levels if the signal repetition rate drops below 100 Hz default or below the low frequency limit set by enter ing a value between 1 Hz and 50 kHz in the menu Auto Trig Low Freq You can reach it by pressing SETTINGS Misc Measuring Functions Phase What is Phase Phase is the time difference between two sig nals of the same frequency expressed as an angle Fig 4 18 Phase delay The traditional method to measure phase de lay with a timer counter is a two step process consisting of two consecutive measurements first a period measurement and immediately after that a time interval measurement The phase delay is then mathematically calcula
31. tain value fiow then you can enter this value from a value input menu The range for flow is 1 Hz to 100 kHz and the default value is 100 Hz The higher value the faster measure ment speed due to more rapid trigger level voltage detection Even faster measurement speed can be reached by setting the trigger levels manually See Trig below Follow the instructions here to change the low frequency limit Press SETTINGS Misc Auto Trig Low Freq Use the UP DOWN arrow keys or the nu meric input keys to change the low fre quency limit to be used during the trigger level calculation default 100 Hz Confirm your choice and leave the SET TINGS menu by pressing EXIT OK three times Trig Value input menu for entering the trigger level manually Use the UP DOWN arrow keys or the nu meric input keys to set the trigger level A blinking underscore indicates the cursor po sition where the next digit will appear The LEFT arrow key is used for correction i e Input Signal Conditioning deleting the position preceding the current cursor position Frequency A Meas 50 000 001 76 mz Input A Trig 9 45 U Fig 3 9 Value input menu for setting the trigger level NOTE It is probably easier to make small ad justments around a fixed value by us ing the arrow keys for incrementation or decrementation Keep the keys de pressed for faster response NOTE Switching o
32. the mea surement the counter will behave like a volt meter with a sample and hold feature and will freeze the result of the previous measurement Time Out Mainly for GPIB use you can manually select a fixed time out in the menu reached by press ing SETTINGS Misc Timeout The range of the fixed timeout is 10 ms to 1000 s and the default setting is Off Select a time that is longer than the cycle time of the lowest frequency you are going to mea sure multiply the time by the prescaling fac tor of the input channel and enter that time as time out 4 10 Theory of Measurement When no triggering has occurred during the time out the counter will show NO SIGNAL Measuring Speed The set measurement time determines the measuring speed for those functions that uti lize averaging Frequency and Period Avg For continuous signals Speed x readings s by when Auto trigger is on and can be increased to Speed readings s te 0 001 when Manual trigger is on or via GPIB Speed x readings s te 000012 m Average and Single Cycle Measurements To reduce the actual gate time or measuring aperture the counters have very short mea surement times and a mode called Single for period measurements The latter means that the counter measures during only one cycle of the input signal In applications where the counter uses an input channel with a prescaler the Single measurement will last as many cy cles
33. 03 lt 1 8x1 Us 2 years after calibration 1 5x10 1 2x10 3 6x10 Typical total uncertainty for op erating temperature 20 C to 26 C 26 95 confidence interval 6 8 8 1 year after calibration lt 7x1 On 6x1 D 1 7x1 D 2 years after calibration 1 2x10 1 2x10 lt 3 5x10 Explanations D Negligible in comparison with the deviation caused by 1 C temperature change 2 After 1 month of continuous operation NOTE Electrical adjustment by means of tuning voltage from DAC no potentiometer trimming Serial interface to all optional oscillators for closed case calibration and status reporting UCXO Uncompensated Crystal Oscillator OCXO Oven Controlled Crystal Oscillator Timebase Options 8 14 Chapter 9 index Index Index 1 cyclecounterror 4 9 A AC DC coupling 3 3 Allan deviation 6 3 AM modulated signals 4 8 Aperture See Measuring time Arming description aus nere 5 5 examples 005 5 9 manually 5 6 syne delay i iouis prora 5 7 Attenuator used to reduce noise 3 7 Auto titmeout sso heed deen Rs 4 10 Auto once cocci eee ee bias 3 5 Auto trigger 3 8 4 16 6 4 how tO USe 2 2 2 ee eee 3 8 Averaging 2 4 10 6 2 B Blank digits 2 rk wads 2 14 Burst Frequency CW C Carrier wave frequency AM Carrier wave freq
34. 19 Selecting Math formula for postprocessing Select one of the five different formulas where K L and M are constants that the user can set to any value X stands for the current non modified measurement result Frequency A MATH MEAS 00 975 813 646 mz Math Limit Math Math K L M K K LIM 1E0 0 EO 1E0 Fig 2 20 Selecting formula constants Each of the softkeys below the constant labels opens a value input menu like the one below Use the numeric input keys to enter the man tissa and the exponent and use the EE key to toggle between the input fields The key marked Xo is used for entering the display reading as the value of the constant 2 12 Description of Keys The Limit submenu is treated in a similar way and its features are explored beginning Frequency A Meas 00 000 001 76 mz Math Limit Math K DEE 0 EE Xo Fig 2 21 Entering numeric values for constants on page 6 6 m User Options Frequency fi nean 10 000 000 O00 4 mz User options Calibrate Test Digits E Recall Interface 0 Fig 2 22 About The User Options menu From this menu you can reach a number of submenus that do not directly affect the mea surement You can choose between a number of modes by pressing the corresponding softkey Save Recall Menu Frequency A Meas 00 000 001 77 mz User options Save Recall Save Setup current Recall Modify pro
35. Duration where i fran fo Modulation signal fmodulation Fig 4 6 Frequency modulation In the worst case exactly half a modulation cycle would be uncompensated for giving a maximum uncertainty of Afmax tmeasuring x foa ulation X TU fo Trea For very accurate measurements of the carrier wave frequency fo measure on the unmodulated signal if it is accessible m Modulation Frequencies above 1 kHz Turn off SINGLE Set a long measurement time that is an even multiple of the inverse of the modu lation frequency You will obtain a good approximation when you select a long measurement time for in stance 10 s and when the modulation fre quency is high above 1000 Hz m Low Modulation Frequencies Press SETTINGS STAT and make the No of samples parameter as large as possi ble considering the maximum allowed mea surement time Press STAT PLOT and let the Measuring Functions counter calculate the mean value of the sam ples You will usually get good results with 0 1 s measurement time per sample and more than 30 samples n 30 You can try out the opti mal combination of sample size and measure ment time for specific cases It depends on the actual fo and Afmax Here the sampling frequency of the measure ment 1 measurement time is asynchronous with the modulation frequency This leads to individual measurement results which are ran domly higher and lo
36. Filter I AC 50n 1x Man ou Off Fig 2 7 Input settings menu By depressing this key the bottom part of the display will show the settings for Input A B The active settings are in bold characters and can be changed by depressing the correspond ing softkey below the display You can also move the cursor indicated by text inversion to the desired position with the RIGHT LEFT arrow keys and then change the active setting with the ENTER key The selections that can be made using this menu are e Trigger Slope positive or negative indi cated by corresponding symbols e Coupling AC or DC Using the Controls Impedance 50 Q or 1 MQ Attenuation 1x or 10x e Trigger Manual or Auto Trigger Level numerical input via front panel keyboard If Auto Trigger is active you can change the default trigger level manually as a percentage of the amplitude e Filter On or Of Notes 1 Always Auto when measuring risetime or falltime 2 The absolute level can either be adjusted using the up down arrow keys or by pressing ENTER to reach the numerical input menu 3 Pressing the corresponding softkey or ENTER opens the Filter Settings menu See Fig 2 8 You can select a fixed 100 kHz analog filter or an adjustable digital filter The equivalent cutoff frequency is set via the value input menu that opens if you select Digital LP Frequency from the menu Frequency fi Meas 50 000 001 76 mz Input A F
37. Freq menu Select A B or C as measurement input Press SETTINGS and Burst Select a Meas Time that is shorter than the burst duration minus two CW cycles If you do not know the approximate burst pa rameters of your signal always start with a short measurement time and increase it gradu ally until the readout gets unstable Press Sync Delay and enter a value lon ger than the burst duration and shorter than the inverse of the PRF See Fig 4 3 Measuring Functions m Selecting Measurement Time Arm Start delay jeg time J W Ar Burst Sync delay Burst Signal Sync delay Fig 4 3 Set the sync delay so that it ex pires in the gap between the bursts Press Start Delay and enter a value lon ger than the transient part of the burst pulse Select Frequency Limit 160 300 MHz if Input A or Input B is to be used Use the low limit if possible to minimize the number of cycles necessary to make a measurement Press EXIT OK to measure All relevant burst parameters can be read on the display simultaneously Fig 4 4 Three time values must be set to measure the correct part of a burst The measurement time must be shorter than the duration of the burst If the measurement continues during part of the burst gap no mat ter how small a period of time then the mea surement is ruined Choosing a measurement time that is too short is better since it onl
38. Hz 300 MHz Input B 0 002 Hz 300 MHz Input C 100 MHz 3 GHz PM6690 6 300 MHz 8 GHz PM6690 7 Resolution 12 digits s m Display Main Parameter Aux Parameters Frequency Vmax Vmin Vp p 8 2 Introduction Frequency Burst A B C Frequency and PRF of repetitive burst signals can be measured without external control sig nal and with selectable start arming delay Functions Frequency in burst Hz PRF Hz Number of cycles in burst Range A B C See Frequency A B C Min Burst Duration 40 ns 80 ns gt 160 MHz Min No of Pulses in Burst Inp A B 3 6 above 160 MHz Inp C 3 x prescaler factor PRF Range see also Inp C spec 0 5 Hz 1 MHz Start Delay Range 10 ns 2 s resolution 10 ns m Display Main Parameter Aux Parameters Frequency in burst PRF amp number of cycles in burst Ch A or Ch B only Period A B C Average m Range Input A B 3 3 ns 500 s Input C 3 GHz 330 ps 10 ns 8 GHz 125 ps 3 3 ns Resolution 12 digits s m Display Main Parameter Period Aux Parameters Vmax Vmin Vp p Period A B Single Range A B 3 3 ns 1000 s Resolution 100 ps m Display Main Parameter Period Aux Parameters Vmax Vmin Vp p Ratio A B B A C A C B 10 to 10 one pass measurem values 1 with reduced resolution 100 Hz to 300 MHz Full input C range Range Freq Range A B Freq Range C m Display Main Parameter Rat
39. Manual FREQA Set Measuring Time Trigger Level A B MS Unique Input Trigger Fig 5 4 Auto arming using the trigger level on B as qualifier The Measurement Process 5 7 Measurement Control Fig 5 5 Measurement control flow diagram 5 8 The Measurement Process Measurement Control Arming Setup Time The arming logic needs a setup time of about 5 nanoseconds before the counter is really armed see Fig 5 6 Arming Signal Measured Signal i 1 a P Setup Time Fig 5 6 Time from active external control edge until measurement is armed When arming delay is selected the setup time is different see Fig 5 7 It illustrates the ef fect of the 100 ns delay resolution Arming Signal Programmed Measured Delay Signal m i Setup Time range from 60 to 40ns Fig 5 7 Time from expired time delay un til measurement is armed 60 to 40 ns Fig 5 7 shows that a start trigger signal may be detected although it appears 60 nanosec onds before the programmed time delay has expired The start trigger signal must come 40 nanoseconds after the programmed time delay has expired to guarantee correct start of the measurement Arming Examples Introduction to Arming Examples The following arming examples are available 1 Measuring the first pulse in a burst 2 Measuring the secon
40. Press Math and choose the expression K X L by pressing the softkey below it Now the display will show the deviation from the value you have just entered By changing the constant K you can scale the result instead Use the expression X M 1 if you want the re sult to be displayed as a relative deviation Statistics Statistics can be applied to all measuring func tions and can also be applied to the result from Mathematics The available statistics functions are as fol lows X MAX Displays the maximum value within a sampled population of N xi values XMIN Displays the minimum value within a sampled population of N xj values X P P Displays the peak to peak deviation within a sampled population of N Xj values MEAN Displays the arithmetic mean value x of a sampled population of N xi values and is calculated as N X a Xi Nia ST DEV Displays the standard deviation s of a sampled population of N x val ues and is calculated as It is defined as the square root of the variance A DEV Displays the Allan deviation c of a sampled population of N xj values and is calculated as Process It is defined as the square root of the Allan variance The number N in the expressions above can assume any value between 2 and 2102 Allan Deviation vs Standard Deviation The Allan Deviation is a statistic used for characterizing short term instability e g caused by jitter and flutter by means
41. Signal Conditioning higher frequencies than the fundamental sig nal m Digital Lowpass Filter The digital LP filter utilizes the Hold Off function described below With trigger Hold Off it is possible to insert a deadtime in the input trigger circuit This means that the input of the counter ignores all hysteresis band crossings by the input signal during a preset time after the first trigger event When you set the Hold Off time to approx 75 of the cycle time of the signal erroneous triggering is inhibited around the point where the input signal returns through the hysteresis band When the signal reaches the trigger point of the next cycle the set Hold Off time has elapsed and a new and correct trigger will be initiated Instead of letting you calculate a suitable Hold Off time the counter will do the job for you by converting the filter cutoff frequency you enter via the value input menu below to an equivalent Hold Off time enn LP Frea EID kHz s Value input menu for setting the cutoff frequency of the digital fil ter Fig 3 7 You should be aware of a few limitations to be able to use the digital filter feature effectively and unambiguously First you must have a rough idea of the frequency to be measured A cutoff frequency that is too low might give a perfectly stable reading that is too low In such a case triggering occurs only on every 2nd 3 4 Input Amplifier 3rd or 4th cycle A cu
42. TH LIM menu to enter this value as the constant L in the for mula K X L by pressing Xo and change sign Now the current measurement result Xo will be subtracted from the future phase measure ments made by selecting Phase A rel B A considerable part of the systematic phase er rors will thus be cancelled out Note that this calibration has to be repeated if the frequency or the amplitude changes Method 2 Connect one of the signals to be measured to both Input A and Input B via a 50 Q power splitter or a BNC T piece depending on the source impedance Make sure the cable lengths between power splitter T piece and instrument inputs are equal Select the func tion Phase A rel B and read the result Enter this value as a correction factor in the same way as described above for Method 1 In order to minimize the errors you should also maintain the signal amplitudes at the in puts so that the deviation between calibration and measurement is kept as small as possible The same restrictions as for Method 1 regard ing frequency and amplitude apply to this method i e you should recalibrate whenever one of these signal parameters changes Residual Systematic Error By mathematically on the bench or in the controller applying corrections according to one of the methods mentioned above the sys tematic error will be reduced but not fully eliminated The residual time delay error will most probably be negligible but a tri
43. The current selection is indicated by text in version that is also indicating the cursor posi tion Select the measurement function you want by depressing the corresponding softkey right below the display Alternatively you can move the cursor to the wanted position with the RIGHT LEFT arrow keys Confirm by pressing ENTER A new menu will appear where the contents depend on the function If you for instance have selected Frequency you can then select between Frequency Frequency Ratio and Frequency Burst Finally you have to decide which input channel s to use Autoset Preset By depressing this key once after selecting the wanted measurement function and input chan 2 6 Description of Keys nel you will most probably get a measure ment result The AUTOSET system ensures that the trigger levels are set optimally for each combination of measurement function and input signal amplitude provided rela tively normal signal waveforms are applied If Manual Trigger has been selected before pressing the AUTOSET key the system will make the necessary adjustments once Auto Once and then return to its inactive condition AUTOSET performs the following functions Setautomatic trigger levels Switch attenuators to 1x Turn on the display By depressing this key twice within two sec onds you will enter the Preset mode and a more extensive automatic setting will take place In addition to the functions above the followi
44. The default value is 200 ms but can be changed via SETTINGS Meas Time between 20 ns and 1000 s The default value gives 11 digits on the dis play and 4 to 5 measurements each second Varying the measurement time is a hardware based averaging method in contrast to the software based mean value function that can be found in the STAT PLOT menu The measurement time changes in 1 2 5 steps if you use the arrow keys for stepping By us ing the numeric entry keys you can set any value within the specified range with a resolu tion of 20 ns To quickly select the lowest mea surement time enter 0 The counter will select 20 ns auto matically Gate Indicator The GATE LED is on when the counter is busy counting input cycles Single Measurements SINGLE is implicitly the normal measure ment mode which means that the counter 5 2 About This Chapter shows the results from a single input cycle The exceptions are Frequency and Period Average Single or Average is not relevant for Vmax Vmin or Vpp measurements Hold Run amp Restart Pressing HOLD completes the current mea surement and freezes the result on the display Pressing RESTART initiates a new measure ment If you are performing a statistics measurement and press HOLD the pending sample will be finished Then the measurement will stop and you can for instance watch the graphic repre sentation of the samples taken so far Pressing RESTART starts a n
45. TimeView M software package will do this measurement quickly and easily li li MI Mi Voltage step generator Input E Ext Arm Input A Fig 5 16 Setup for transient profiling of a VCO Eile Rr Capture malyze Yiew Print Config Help us ue 1 5 pre m i B LJ 150 us sm Samples Fig 5 17 Results from a transient profiling measurement Chapter 6 Process Process Introduction Three different ways to process a measuring result are available Averaging Mathematics and Statistics They can be used separately or all together In addition to postprocessing you can also monitor the measurement results in real time by setting limits and deciding how to react when they are crossed Averaging Hardware averaging by means of counting clock pulses during several full input signal cycles is only used for the measurement func tions Frequency and Period Average The parameter to be set by the operator in this case is Meas Time under SETTINGS and the range is 20 ns to 1000 s Longer measuring times mean higher resolution The other functions employ single cycle mea suring and the method to get average results is to utilize the statistics features described later Mathematics The counter can use five mathematical expres sions to process the measurement result before it is
46. User Options About you can find information on firmware version and calibration date See page 2 12 Installation Supply Voltage W Setting The Counter may be connected to any AC supply with a voltage rating of 90 to 265 Vrms 45 to 440 Hz The counter automati cally adjusts itself to the input line voltage m Fuse The secondary supply voltages are electroni cally protected against overload or short cir cuit The primary line voltage side is protected by a fuse located on the power supply unit The fuse rating covers the full voltage range Consequently there is no need for the user to replace the fuse under any operating condi tions nor is it accessible from the outside Unpacking 1 7 Preparation for Use CAUTION If this fuse is blown it is likely that the power supply is badly damaged Do not replace the fuse Send the counter to the local Service Center Removing the cover for repair maintenance and adjustment must be done by qualified and trained personnel only who are fully aware of the hazards involved The warranty commitments are rendered void if unauthorized access to the interior of the instrument has taken place during the given warranty period Grounding QD Grounding faults in the line voltage supply will make any instrument connected to it dan gerous Before connecting any unit to the power line you must make sure that the pro tective ground functions correctly Only then can a unit be conn
47. adjusting reris ess REC Eis 2 7 LIMIS oer ct ceetrca cee mae baee bo es 6 6 LOCALLOCKOUT Mode 2 7 LOCAL Mode 2 0 2 7 Long time instability 6 4 Low pass filter digital irm amm 3 4 M Manual ANMING Sih genes ee des Ru oss 5 6 Mathematics and Statistics together 6 5 constants 6 2 example oie ccd ens IS Re gees 6 2 f ncti ni esl back terns 6 2 Meam iai koc pP moans 6 3 E M Index Measurement ME MP 5 4 free running geca gupes iee 5 13 fale acs ppn irain ee RES 5 5 Stafa ope RE ERR ERA E 5 4 UUMING 2 22er eI E RR 5 4 Measurement rate 6 4 Measurement Time SUING sox evs sarge eee ws earns dee 5 2 Measuring speed 4 10 6 4 Measuring time 5 5 influence by prescaling 4 11 Modulating frequency AM 4 9 Monitoring llle 6 2 N No trig display message 4 10 NolS6 va ert Ua ex err weh 3 6 O Options CHECKING sibi 7 11 7 12 OVerrlV8 seem RERO ees 4 15 P PENOG ERES 4 12 Phase inaccuracies 4 18 Prescaling CECE Of ov seo ee bod 4 11 Processing a measuring result 6 2 Profiliigss oria Rega 5 9 5 13 transient 0 4 5 14 VCO step response 5 14 Pulse period 4 12 Pulse rounding 4 16 Pulse Width description 4 15 R Rate of measurement 5 5 Ratio
48. an perform jitter analysis on several tens of thou sands of pulse width measurements and cap ture them in a second An extensive programming manual helps you understand SCPI and counter programming The counter is easy to use in GPIB environ ments A built in bus learn mode enables you to make all counter settings manually and transfer them to the controller The response can later be used to reprogram the counter to the same settings This eliminates the need for the occasional user to learn all individual pro gramming codes Complete manually set counter settings can also be stored in 20 internal memory locations and can easily be recalled on a later occasion Ten of them can be user protected Preparation for Use Safety Introduction Even though we know that you are eager to get going we urge you to take a few minutes to read through this part of the introductory chapter carefully before plugging the line con nector into the wall outlet This instrument has been designed and tested for Measurement Category I Pollution Degree 2 in accordance with EN IEC 61010 1 2001 and CAN CSA C22 2 No 61010 1 04 in cluding approval It has been supplied in a safe condition Study this manual thoroughly to acquire ade quate knowledge of the instrument especially the section on Safety Precautions hereafter and the section on nstallation on page 1 7 Safety Precautions All equipment that can be connected to line po
49. ar 8 2 Measurement Functions 8 2 FrequencyA B C 8 2 Frequency Burst A B C 8 2 Period A B C Average 8 2 Period A B Single 8 3 Ratio A B B A C A C B 8 3 Time Interval A to B B to A Ato A BOB mue concierto EM 8 3 Pulse WidthA B 8 3 Rise and Fall Time A B 8 3 Phase A Rel B B Rel A 8 4 Duty Factor A B 8 4 Vac Vmi Vpp A B aes eee 8 4 Timestamping A B C 8 5 Auto Set Manual Set 8 5 Input and Output Specifications 8 5 Inputs AandB 8 5 Input C PM6690 6xx 8 6 Input C PM6690 7xx 8 6 Rear Panel Inputs amp Outputs 8 6 Auxiliary Functions 8 7 Trigger Hold Off 8 7 External Start Stop Arming 8 7 Statistics eos tees 8 7 Mathematics 05 8 7 Other Functions 8 7 Display mie sree t bebe tee ered echoed sbeient 8 8 GPIB Interface 8 8 USB Interface nice a eed tele ans 8 8 TimeView 0 0 0 0 0 0 00 2 eae 8 8 Measurement Uncertainties 8 10 Random Uncertainties 10 8 10 Systematic Uncertainties 8 10 Total Uncertainty 26 8 10 Time Interval Pulse Width Rise Fall MME uisi id to tn n eret cunc 8 10 Frequency amp Period 8 10 Frequency Ratio fi fa
50. as set the LIM flag The measurement process will stop and the value that caused the limit de tector to trigger can be read on the dis play Only samples taken before the alarm condition will be part of the population in statistics presentations The alarm conditions can also be detected via the SRQ function on the GPIB See the Pro gramming Manual Limit Mode The Limit Mode offers three choices Above Results above the set lower limit will pass A flashing LIM symbol on the dis play reports that the measurement re sult has been below the lower limit at least once since the measurement started Use RESTART to reset the LIM symbol to its non flashing state Below Results below the set upper limit will pass A flashing LIM symbol on the dis play reports that the measurement re sult has been above the upper limit at least once since the measurement started Use RESTART to reset the LIM symbol to its non flashing state Range Results inside the set limits will pass A flashing LIM symbol on the display re ports that the measurement result has been below the lower limit or above the upper limit at least once since the mea surement started Use RESTART to reset the LIM symbol to its non flashing Process This type of graphic resembles a classic ana log pointer instrument where the pointer is a happy smiley as long as it is positioned inside the limits and a sad smiley when it gets outside the limit
51. as the division factor If you want to mea sure with a very short aperture use an input with a low division factor Averaging is the normal mode for frequency and period measurements when you want to reach maximum resolution There is always a tradeoff between time and precision however so decide how many digits you need and use as short a measurement time as possible to ar rive at your objective Measuring Functions m Prescaling May Influence Function Prescaling Measurement Time Factor Prescalers do affect the minimum measure FREQ A B 300 MHz 2 ment time inasmuch as short bursts have to BURST A B 160 MHz 1 contain a minimum number of carrier wave periods This number depends on the BURST A B gt 160 MHz 7 prescaling factor PERIOD A B AVG 300 MHz 2 PERIOD A B SGL 300 MHz 1 AWWW ae opal i FREQ C 8 GHz 256 All other functions 1 After 1 16 prescaler 16 periods Fig 4 11 Divide by 16 Prescaler Fig 4 11 shows the effect of the 3 GHz prescaler For 16 input cycles the prescaler gives one square wave output cycle When the counter uses a prescaler it counts the number of prescaled output cycles here f 16 The dis play shows the correct input frequency since the microcomputer compensates for the effect of the division factor d as follows nxd f by Prescalers do not reduce resolution in recipro cal counters The relative quantization error is 100 ps
52. ation ON plus set measurement time For example with a measurement time of 0 1 ms the time between each sample is ap proximately 104 108 us m Repetitive Sampling Profiling The measurement setup just described will not work when the profiling demands less than 4 us intervals between samples How to do a VCO step response profil ing with 100 samples during a time of 10 ms This measurement scenario requires a repeti tive input step signal and you have to repeat your measurement 100 times taking one new sample per cycle And every new sample should be delayed 100 us with respect to the previous one The easiest way to do this is by means of a controller e g a PC although it is possible but tedious to manually set and perform all 100 measurements The following are required to setup a mea surement A repetitive input signal e g frequency output of VCO An external SYNC signal e g step volt age input to VCO Use of arming delayed by a preset time e g 100 200 300 us See Fig 5 16 and Fig 5 17 5 14 Arming Examples When all 100 measurements have been made the results can be used to plot frequency ver sus time Note that the absolute accuracy of the time scale is dependent on the input signal itself Although the measurements are armed at 100 us 100 ns intervals the actual start of measurement is always synchronized to the first input signal trigger event after arming The
53. ault settings and make the following changes Press MEAS FUNC Time Press EXIT OK Press STAT PLOT key to the right of the display Settings for INPUT A and INPUT B DC coupling 50 Q input impedance MANual trigger level Trig level 0 5 V Press EXIT OK twice The standard deviation Std should be lt 100 ps Performance Check Rear Inputs Outputs 10 MHz OUT Connect an oscilloscope to the 10 MHz output on the rear of the counter Use a coaxial cable and 50 Q termination The output voltage should be sinusoidal and above 1 Vrms 2 8 Vp p EXT REF FREQ INPUT Recall the DEFAULT settings Connect a stable 10 MHz signal e g REF OUT from another counter to input A Connect a 10 MHz 100 mVnMs 0 28 Vp p signal from the LF synthesizer to EXT REF IN Select Ext Ref by keying in the following sequence SETTINGS Timebase Ref Ext Press EXIT OK Change the external reference frequency to 5 and 1 MHz The counting should continue and the dis play should still show 10 MHz EXT ARM INPUT Proceed from the test above Select INPUT A MANual trigger Press EXIT OK Connect the pulse generator to Ext Arm Input Settings for the pulse generator single shot pulse manual trigger amplitude TTL 0 2 Vpp and duration 10 ns Rear Inputs Outputs 7 9 Performance Check Activate start arm
54. be reliable at least two measurements must be made the first to synchronize the measure ment and the second from which the measure ment result can be read out 4 6 Frequency Modulated Signals Frequency Modulated Signals A frequency modulated signal is a carrier wave signal CW frequency fo that changes in frequency to values higher and lower than the frequency fo It is the modulation signal that changes the frequency of the carrier wave The counter can measure fo Carrier frequency fmax Maximum frequency fmin Minimum frequency Af Frequency swing fmax fo Carrier Wave Frequency f To determine the carrier wave frequency mea sure fmean Which is a close approximation of fo Press STAT PLOT to get an overview of all the statistical parameters Select the measurement time so that the coun ter measures an integral number of modulation periods This way the positive frequency devi ations will compensate the negative deviations during the measurement Example If the modulation frequency is 50 Hz the measurement time 200 ms will make the counter measure 10 complete modu lation cycles If the modulation is non continuous like a voice signal it is not possible to fully com pensate positive deviations with negative deviations Here part of a modulation swing may remain uncompensated for and lead to a measuring result that is too high or too low Worst Case Measuring Time e r
55. d pulse in a burst 3 Measuring the time between pulse 1 and 4 in a burst 4 Profiling Examples 1 and 2 measure the pulse width of a selected positive pulse in a burst You can however also measure the period rise time or duty factor by changing FUNCTION and you can measure on a negative pulse by changing trigger slope If you do not know the basic parameters of the signal to be measured we recommend to use an oscilloscope for monitoring Then you can estimate roughly how to set trigger slope arming slope and arming delay 1 Measuring the First Burst Pulse Sync E a LILIL BL a ee a Input A Fig 5 8 Synchronizing the measurement so that the pulse width of the first pulse is measured In the first example we will measure the width of pulse 1 in a repetitive pulse burst In this example a synchronization signal SYNC with TTL levels is also available See Fig 5 8 However the quick and simple method de Arming Setup Time 5 9 Measurement Control scribed first does not employ arming at all but rather draws on the fact that a counter of this type tends to self synchronize its internal pro cesses to the input signal Our task is to synchronize the start of the mea surement start trigger to the leading edge of the first pulse Depending on the signal tim ing this can be easy difficult or very diffi cult m A Auto Synchronization Without Arming If we are lucky we can ma
56. d theoretically span up to 2 10 s or more than 60000 years Jitter Time Interval or Frequency Fig 6 1 Jitter and drift Statistics and Mathematics The counter allows you to perform mathemat ical operations on the measured value before it is presented to the display or to the bus See Page 6 2to get an overview of the four avail able equations Any systematic measurement uncertainty can be measured for a particular measurement setup and the needed correction constants can be entered into these equations Statistics will then be applied to the corrected measured value Confidence Limits The standard deviation can be used to calcu late the confidence limits of a measurement Confidence limits ksx Where sx standard deviation Process k 1 for a confidence level of 68 3 16 limits k 7 2 for a confidence level of 95 596 20 limits k 3 for a confidence level of 99 7 3o limits m Example A measurement of a time interval of 100 us is used to illustrate how the confidence limits are calculated from the measurement result Use the statistics to determine the mean value and standard deviation of the time interval Take sufficient samples to get a stable reading Assume further that the start and stop trigger transitions are fast and do not contribute to the measurement uncertainties The counter dis plays MEAN value 100 020 us and a STD DEV 50 ns then the 95 5 con
57. de changes to Remote indi cated by the label Remote on the display The main measurement result and the input set tings are displayed in this mode Entering Numeric Values Sometimes you may want to enter constants and limits in a value input menu for instance one of those that you can reach when you press the MATH LIMIT key You may also want to select a value that is not in the list of fixed values available by pressing the UP DOWN arrow keys One example is Meas Time under SETTINGS A similar situation arises when the desired value is too far away to reach conveniently by incrementing or decrementing the original value with the UP DOWN arrow keys One example is the Trig Lvl setting as part of the INPUT A B settings Whenever it is possible to enter numeric val ues the keys marked with 0 9 decimal point and stands for Change Sign take on their alternative numeric meaning It is often convenient to enter values using the scientific format For that purpose the rightmost softkey is marked EE stands for Enter Exponent making it easy to switch be tween the mantissa and the exponent Press EXIT OK to store the new value or CANCEL to keep the old one Hard Menu Keys These keys are mainly used for opening fixed menus from which further selections can be made by means of the softkeys or the cur sor select keys m Input A B Frequency A II 10 000 040 45 mz Input A Bc ia i x fete Trig
58. e Duty requires 2 measurement steps Measurement Errors Hysteresis The trigger hysteresis among other things causes measuring errors see Figure 4 16 Ac tual triggering does not occur when the input signal crosses the trigger level at 50 percent of the amplitude but when the input signal has crossed the entire hysteresis band Start SS Trigger level Stop Channel B _Measured Time Interval Fig 4 16 Trigger hysteresis The hysteresis band is about 20 mV with at tenuation 1x and 200 mV with attenuation 10x To keep this hysteresis trigger error low the attenuator setting should be 1x when possible Use the 10x position only when input signals have excessively large amplitudes or when you need to set trigger levels higher than 5 V Pulse Width A B 4 15 Measuring Functions Overdrive and Pulse Rounding Additional timing errors may be caused by triggering with insufficient overdrive see Fig ure 4 17 When triggering occurs too close to the maximum voltage of a pulse two phenom ena may influence your measurement uncer tainty overdrive and rounding Trigger level Actual triggering Crossing trigger level Fig 4 17 Insufficient overdrive causes Trigger Error Overdrive When the input signal crosses the hysteresis band with only a mar ginal overdrive triggering may take some 100 ps longer than usual The specified worst case 500 ps
59. e ae 3 3 Converting Auto to Manual 3 5 howtouse ls eese 3 7 setting speed 3 5 V VCO step response profiling 5 14 Voltage checking 4 7 6 TUNCHON ues re a 4 22 X X MaX a tise geam bs irs aes ee Rn 6 3 X MIN ere redes in Re Pn ac 6 3 Index This page is intentionally left blank Chapter 10 Service Sales and Service office For service information contact your Fluke service center To locate an autho rized service center visit us on the World Wide Web www fluke com or call Fluke using any of the phone numbers listed below 888 993 5853 in U S A and Canada 31 0 40 2675 200 in Europe 1 425 446 5500 from other countries
60. e rear panel Put the two screws A back Fasten the brackets at the left and right side with the screws included as illustrated in Fig 1 3 Fasten the instrument in the rack via screws in the four rack mounting holes The long bracket has an opening so that cables for Input A B and C can be routed inside the rack m Reversing the Rackmount Kit The instrument may also be mounted to the right in the rack To do so swap the position of the two brackets 1 10 Unpacking Chapter 2 Using the Controls Using the Controls A more elaborate description of the front and rear panels including the user interface with Basic Controls its menu system follows after this introductory INPUT A Opens the menu from which you can adjust all settings for Input A like Coupling Impedance and Attenuation INPUT B Opens the menu from which you can adjust all settings for Input B like Coupling Impedance and Attenuation survey the purpose of which is to make you familiar with the layout of the instrument SETTINGS Select measurement pa rameters such as mea surement time number of measurements and so on 7 4 FLUKE PM6690 FREQUENCY CC UNTER TIMER ANALYZER 100ps 300MHz AUTO SET EXIT OK D 0 Cw s P 7 R 300MHz E RALI LALJZLILIJIJL INPUTA INPUT s ER usum luser carl ouod Resa m3 MAX 5 fa
61. eans that the set number of samples will be taken with minimum delay Press HOLD RUN to stop the measuring process Press RESTART to initiate one data cap ture Toggle STAT PLOT to view the measure ment result as it is displayed in the differ ent presentation modes Note that you can watch the in termediate results update the display continually until the com plete data capture is ready This is particularly valuable if the collection of data is lengthy Measuring Speed When using statistics you must take care that the measurements do not take too long time to perform Statistics based on 1000 samples does not give a complete measurement result until all 1000 measurements have been made although it is true that intermediate results are displayed in the course of the data capture Thus it can take quite some time if the setting of the counter is not optimal 6 4 Statistics Here are a few tips to speed up the process Do not use AUTO trigger It is convenient but it takes a fraction of a second each time the timer counter determines new trigger levels and 1000 or 10000 times a fraction of a second is a long time Do not use a longer measuring time than necessary for the required resolution Remember to use a short pacing time if your application does not require data col lection over a long period of time Determining Long or Short Time Instability When making statistical measu
62. ected to the power line and only by using a three wire line cord No other method of grounding is permitted Extension cords must always have a protective ground conductor CAUTION If a unit is moved from a cold to a warm environment con densation may cause a shock hazard Ensure therefore that the grounding requirements are strictly met WARNING Never interrupt the grounding cord Any interruption of the protective ground connection inside or outside the instrument or disconnection of the protective ground terminal is likely to make the instrument dangerous 1 8 Unpacking Orientation and Cooling The counter can be operated in any position desired Make sure that the air flow through the ventilation slots at the top and side panels is not obstructed Leave 5 centimeters 2 inches of space around the counter Fold Down Support Fig 1 2 Fold down support for comfort able bench top use For bench top use a fold down support is available for use underneath the counter This support can also be used as a handle to carry the instrument Rackmount Adapter nomen agen Fig 1 3 Dimensions for rackmounting hardware If you have ordered a 19 inch rack mount kit for your instrument it has to be assembled af ter delivery of the instrument The rackmount kit consists of the following 2 brackets short left long right 4 screws M5 x 8 4 screws M6 x 8
63. efault Settings 2 15 3 Input Signal Conditioning Input Amplifier 3 2 Impedance ils de d 3 2 Attenuation casser riemusta mais 3 2 COU PING uli emer ts Gro aas 3 3 FIET eei EDT 3 3 Mam AUTO a e eaea 3 4 TAg uk dah che menm tmb a bab pns 3 5 How to Reduce or Ignore Noise and Interference ius eher ers 3 6 Trigger Hysteresis 3 6 How to use Trigger Level Setting 3 7 4 Measuring Functions Introduction to This Chapter 4 2 Selecting Function 4 2 Frequency Measurements 4 3 FREQ A B iss aee ger heels 4 3 FREQ C siete ashok LEN EEEREN 4 3 RATIO A B B A C A C B 4 4 4 BURST AB C ciu sad ure deme 4 4 Triggering eoe 4 4 Burst Measurements using Manual Hold Run amp Restart 5 2 Preseittihg xr 5 MT SERERE RENE 5 2 Frequency Modulated Signals 4 6 Start Arming 00 5 3 Carrier Wave Frequency fo 4 6 Stop Arming sisse esses 5 3 LR je Controlling Measurement Timing 5 4 Tone da dcc ee Ex yt Roter Duros 4 7 MPO eked tat 4 8 The Measurement Process Bsn gions uitis 5 4 Errors in fna fni and Afpp 4 8 Ee TING 5 ME 5 4 AM Signals sepeser ienris yireseissas 4 8 Measurement Time and Rates 5 5 Carrier Wave Frequency 4 8 What is Arming 5 5 Modulating Frequency 9 Arming Setup Time 0000 5 9 Theory of Measurement
64. egration and low component count reduces power consumption and results in an MTBF of 30 000 hours Modern surface mount technology ensures high production quality A rugged mechanical construction including a metal cabinet that withstands mechanical shocks and protects against EMI is also a valuable feature High Resolution The use of reciprocal interpolating counting in this new counter results in excellent relative resolution 12 digits s for all frequencies The measurement is synchronized with the in put cycles instead of the timebase Simulta neously with the normal digital counting the counter makes analog measurements of the time between the start stop trigger events and the next following clock pulse This is done in four identical circuits by charging an integrating capacitor with a constant current starting at the trigger event Charging is stopped at the leading edge of the first follow ing clock pulse The stored charge in the inte grating capacitor represents the time differ ence between the start trigger event and the leading edge of the first following clock pulse A similar charge integration is made for the stop trigger event When the digital part of the measurement is ready the stored charges in the capacitors are Preface 1 3 Preparation for Use measured by means of Analog Digital Converters The counter s microprocessor calculates the result after completing all measurements i e the
65. elect 50 Q input impedance 1x attenua tion MANual trigger and Trigger level 0 V Connect a signal from a HF generator to a BNC power splitter Connect the power splitter to Input A of your counter and an oscilloscope Set the input impedance to 50 Q on the oscilloscope Adjust the amplitude according to the fol lowing table Read the level on the oscillo scope The timer counter should display the correct frequency Connect the signal to Input B Press INPUT B Select 50 Q input impedance 1x attenua tion MANual trigger and Trigger level 0 V Press MEAS FUNC Freq Freq A B Repeat the measurements above for Input B Frequency Level Pass MHz mVrms dBm Input A Input B 10 15 23 50 15 23 100 15 23 200 15 23 300 25 19 Table 7 3 Sensitivity for inputs A amp B at various frequencies Short Form Specification Test 7 5 Performance Check Voltage Recall the DEFAULT settings Press MEAS FUNC Volt Vpp gt A Press INPUT A and select DC coupling Do not apply an input signal to Input A yet Press EXIT OK The display should now indicate disregard the main parameter Vpp Vmi 0 0 015 V and VMAX 0 0 015 V Connect 2 500 Vpc to Channel A using the external low pass filter on the input The display should now indicate VMIN 2 500 0 040 V and V
66. elow limit 1 Capture amp store values in side limits 1 and 2 Capture amp store values outside limits 1 and 2 Time Range 4 us 500s Equidistancy 2 us 0 1 of pacing time Mathematics Functions K X L K X L K X L M K X L M and X M 1 X is current reading K L and M are constants set via keyboard or as frozen reference value Xo Other Functions Measuring Time Timebase Reference 20 ns 1000 s for Period AVG Frequency and PRF 20 ns 2 s for Freq in Burst Single cycle for other meas functions Times 22 s are software controlled w reduced res olution and accuracy Internal external or auto matic Auxiliary Functions 8 7 Specifications Freezes meas result until a new measurement is ini tiated via Restart Removes blanks 1 to 13 digits from the calculated result before displaying it Display Hold Digit Blanking Limit Alarm Annunciator on display and or SRQ via GPIB Limit Values Lower limit limit 1 Upper limit limit 2 Settings Off Alarm if value gt limit 2 Alarm if value lt limit 1 Alarm if limit 1 lt value lt limit 2 Alarm if value gt limit 2 or value lt limit 1 On Alarm Stop or Continue Display Numeric graphic Numeric Current measurement value annunciator for limit alarm Graphic Horizontal line w up per lower limit markers current value marker Stored Instrument Setups 20 complete setups can be saved and recal
67. en arbitrary trigger levels Rise Fall Time A B These functions can be found under the func tion menu Time 4 14 Time Interval Rise and fall time can be measured on both in put A and input B By convention rise fall time measurements are made with the trigger levels set to 10 start and 90 stop of the maximum pulse amplitude see Figure 4 15 The counter measures the time from when the signal passes 10 of its amplitude to when it passes 90 of its amplitude The trigger lev els are calculated and set automatically Auxiliary parameters shown simultaneously are Slew Rate V s Vmax and Vmin 100 90 Trigger Level B Input A Common Trigger Level A 10 0 Fig 4 15 Trigger levels for rise fall mea surements For ECL circuits the reference levels are 20 start and 80 stop In this case you can use either of two methods 1 Select the general Time Interval function de scribed above and set the trigger levels man ually after calculating them from the abso lute peak values Then you can benefit from the auxiliary parameters Vmax and Vmin For measurements made on input A use the fol lowing settings Rise Time Trig Level A V min 0 2 Vinax Vmin Trig Level B V min 0 8 V max i Vinin Fall Time Trig Level A Vmin 4 Trig Level B Vmin 4 2 Select one of the dedicated Rise Fall Time functions and exploit the possibility to man F0 S V max Vmin
68. ence AUTO No of Bins 20 Blank Digits 0 Default Settings 2 15 Using the Controls This page is intentionally left blank 2 16 Default Settings Chapter 3 Input Signal Conditioning Input Signal Conditioning Input Amplifier The input amplifiers are used for adapting the widely varying signals in the ambient world to the measuring logic of the timer counter These amplifiers have many controls and it is essential to understand how these controls work together and affect the signal The block diagram below shows the order in which the different controls are connected It is not a complete technical diagram but in tended to help understanding the controls The menus from which you can adjust the set tings for the two main measurement channels are reached by pressing INPUT A respec tively INPUT B See Figure 3 2 The active choices are shown in boldface on the bottom line Impedance The input impedance can be set to 1 MQ or 50 Q by toggling the corresponding softkey Frequency fi DERE 10 000 040 45 mz Input A oc We tx avte Trig Filter T AC 50n ix Man 0U Off Fig 3 2 Input settings menu CAUTION Switching the impedance to 50 Q when the input voltage is above 12 Vrms may cause perma nent damage to the input circuitry Attenuation The input signal s amplitude can be attenuated by 1 or 10 by toggling the softkey marked 1x 10x Use attenuation whenever the input s
69. er 24 hours of oscillators to measure initial drift of a generator during a 30 minute warm up time or to measure short term sta bility during 1 or 10s In these cases measure ments are performed at user selected intervals in the range 2 us to 1000 s There are several different ways of performing the measure ments at regular intervals Measurements using the statistics features for setting the pacing time By setting the pacing time to 10 s for exam ple measurements are automatically made at 10 s intervals until the set number of samples has been taken The range is 2 2 10 Use HOLD RUN and RESTART if you want to stop after one full cycle You can watch the trend or spread on the graphic display while the measurement is proceeding Using a controller as a pacer As an alternative the timer in the controller can be used for pacing the individual measure ments This allows for synchronization with external events for instance a change of DUT when checking a series of components Using external arming signals External arming signals can also be used for pacing For example with an arming signal consisting of 10 Hz pulses individual mea surements are armed at 100 ms intervals Letting the counter run free When the counter is free running the shortest delay between measurements is approximately 4 us internal calibration OFF or 8 us inter Arming Examples 5 13 Measurement Control nal calibr
70. ew measurement from sample 1 and the measurement will stop when the preset number of samples has been taken Arming Arming gives you the opportunity to start and stop a measurement when an external qualifier event occurs Start and stop of the arming function can inde pendently be set to positive slope negative slope or it can be turned off A delay between 10 ns and 2 s can be applied to the start arm ing channel to facilitate certain measurements The resolution is 10 ns Input E on the rear panel is the normal arming input but also input A and input B can be used The frequency range for input E is 80 MHz whereas it is 160 MHz for the other inputs All the versatile arming functions can be reached under SETTINGS Arm Measurement Control Arming is somewhat complicated yet gives the flexibility to perform a measurement on a specific portion of a complex signal like a frequency measurement on the colorburst con tained in a composite video signal Other examples of arming can be found later in this chapter starting on page 5 9 Start Arming Start arming acts like an ExternalTrigger on an oscilloscope It allows the start of the ac tual measurement to be synchronized to an ex ternal trigger event In a complex signal you may want to select a certain part to perform measurements on For this purpose there is an arming delay func tion which delays the actual start of measure ment with respect to the
71. f manual arm ing A pending measurement will be finished and the result will remain on the display until a new measurement is triggered by pressing the RESTART key m Restart Often this key is operated in conjunction with the HOLD RUN key see above but it can also be used in free running mode especially when long measuring times are being used e g to initiate a new measurement after a change in the input signal RESTART will not affect any front panel settings Using the Controls Default Settings See page 2 13 to see how the following prepro grammed settings are recalled by a few key strokes PARAMETER VALUE SETTING PARAMETER VALUE SETTING Input A amp B Pacing State OFF Trigger Level AUTO Pacing Time 20 ms Trigger Slope POS A NEG B Mathematics Impedance 1 MQ Mathematics OFF Attenuator 1x Math Constants K 1 L 0 M 1 Coupling AC Limits Filter OFF Limit State OFF Arming Limit Mode ABOVE Start OFF Lower Limit 0 Start Slope POS Upper Limit 0 Start Arm Delay 0 Burst Stop OFF Sync Delay 400 us Stop Slope POS Start Delay 0 Hold Off Meas Time 200 us Hold Off State OFF Freq Limit 300 MHz Hold Off Time 200 us Time Out Miscellaneous Time Out State OFF Function FREQA Time Out Time 100 ms Meas Time 200 ms Statistics Smart Time Interval OFF Statistics OFF Auto Trig Low Freq 100 Hz No of Samples 100 Timebase Refer
72. factor is called prescaler factor and can have different values depending on the prescaler type The 3 GHz prescaler is de signed for a prescaling factor of 16 This means that an input C frequency of e g 1 024 GHz is transformed to 64 MHz Prescalers are designed for optimum perfor mance when measuring stable continuous RF Most prescalers are inherently unstable and would self oscillate without an input signal To prevent a prescaler from oscillating a go detector is incorporated See Fig 4 13 The go detector continuously measures the level of the input signal and simply blocks the prescaler output when no signal or a signal that is too weak is present To counting N amp gt logic E Go detector Fig 4 13 Go detector in the prescaler The presence of a burst signal to be measured makes certain demands upon the signal itself Regardless of the basic counter s ability to measure during very short measurement times the burst duration must meet the fol lowing minimum conditions BurStmin gt presc factor x inp cycle time x3 or at least 80 ns Normally the real minimum limit is set by other factors like the speed of the GO detec tor This speed depends on the specific input option used 4 12 PERIOD PERIOD Single A B Average A B C From a measuring point of view the period function is identical to the frequency function This i
73. fidence limits 2sx 2 50 ns 100 ns The 30 limit will then be 3 50 ns 150 ns Jitter Measurements Statistics provides an easy method of deter mining the short term timing instability jit ter of pulse parameters The jitter is usually specified with its rms value which is equal to the standard deviation based on single mea surements The counter can then directly mea sure and display the rms jitter Otherwise the standard deviation of mean values can be measured The rms value is a good measure to quantify the jitter but it gives no information about the distribution of the measurement values To improve a design it might be necessary to analyze the distribution Such measurements as well as trend analysis can be performed by Statistics 6 5 Process means of the built in graphic capability tog gle the STAT PLOT key to see the two graphic presentation modes Even higher versatility can be exploited with a controller and the optional TimeView Fre quency and Time Analyzing Software Pack age Limits The Limits Mode makes the counter an effi cient alarm condition monitor with high flexi bility as to the report possibilities Press MATH LIM Limits to enter the first Limits Menu See below Frequency A Dx 4 134 670 378 mz Math Limit Limits Limit Limit Lower Upper Behavior Mode Limit Limit Off Range 4E3 6 E3 Fig 6 2 The Limit Menu level 1
74. formance Check Trigger Indicators vs Trigger Levels Trigger Level manually set Trigger Indicator Pass Input A Input B 1V off 1V on 0 0V blinking Table 7 4 Trigger indicator check NOTE This test must be performed in the se quence given Recall the DEFAULT settings Press INPUT A and select MANual trigger level and 50 Q input impedance Connect the LF synthesizer to Input A Use the following settings into 50 Q Sine 10 kHz 0 9 Vpp and 0 50 V DC offset Verify that the three modes for the trigger indicator are working properly by chang ing the trigger level Press the Trig key and enter 1 V via the keyboard then verify by pressing EXIT OK Check the trigger indicator according to Table 7 4 Press the Trig key and enter 1 V via the keyboard by pressing the key then verify by pressing EXIT OK Check the trigger indicator according to Table 7 4 Press the Trig key and enter 0 via the keyboard then verify by pressing EXIT OK Check the trigger indicator according to Table 7 4 Apply the signal to Input B instead Press MEAS FUNC gt Freq gt Freq A B Press INPUT B and select MANual trigger level and 50 Q input impedance Repeat the trigger level settings above to verify the three trigger indicator modes for Input B Settings Vmax Vmin Pass Fai
75. gger level error will always remain to a certain ex tent especially if the temperature conditions are not constant Measuring Functions Possible Errors 4 21 Measuring Functions Voltage VMAX VMIN VPP Press MEAS FUNC Volt The counter can measure the input voltage levels VMAX VMIN and Vpp on DC input voltages and on repeti tive signals between 1 Hz and 300 MHz The default low frequency limit is 20 Hz but can be changed via the SETTINGS Miscellaneous menu between 1 Hz and 50 kHz A higher low frequency limit means faster measurements The voltage capacity is 50 V to 50 V in two automatically selected ranges For LF signals the measurement has voltme ter performance i e an accuracy of about 1 of the reading You can select any one of the parameters to be the main parameter that is displayed in large digits and with full resolution while the others are displayed simultaneously at the bottom of the display in smaller characters 4 22 Vmax VMIN VPP The voltage is determined by making a series of trigger level settings and sensing when the counter triggers VRMS When the waveform e g sinusoidal triangu lar square of the input signal is known its crest factor defined as the quotient Qcr of the peak Vp and RMS Vrms values can be used to set the constant K in the mathematical function K X L The display will then show the actual Vims value of the inp
76. gle line numerical pre sentation of individual results where the main parameter is displayed in large characters with Using the Controls full resolution together with a number of aux iliary parameters in small characters with lim ited resolution Frequency A TZ MEAS 49 999 999 62 wiz 49 900 000 000MHz Umax 1 490 U Umin 2 529 U Fig 2 3 50 100 000 000MHz Up p 4 019 U Limits presentation If Limits Alarm is enabled you can visualize the deviation of your measurements in relation to the set limits The numerical readout is now combined with a traditional analog pointer type instrument where the current value is represented by a smiley The limits are presented as numerical values below the main parameter and their positions are marked with vertical bars labelled LL lower limit and UL upper limit on the autoscaled graph If one of the limits has been exceeded the limit indicator at the top of the display will be flashing In case the current measurement is out of the visible graph area it is indicated by means of a left or a right arrowhead m STAT PLOT If you want to treat a number of measure ments with statistical methods this is the key to operate There are three display modes available by toggling the key Numerical Histogram Trend Plot Description of Keys 2 7 Using the Controls Numerical Trend Plot Frequency A MEAN Load Frequency fi 5 000 000
77. gnal slew rate in V s is low for LF sig nals To reduce the trigger uncertainty it is de sirable to cross the hysteresis band as fast as possible Fig 3 14 Low amplitude delays the trig ger point Fig 3 14 shows that a high amplitude signal passes the hysteresis faster than a low ampli tude signal For low frequency measurements where the trigger uncertainty is of importance Input Signal Conditioning do not attenuate the signal too much and set the sensitivity of the counter high In practice however trigger errors caused by erroneous counts Fig 3 10 and Fig 3 12 are much more important and require just the op posite measures to be taken To avoid erroneous counting caused by spuri ous signals you need to avoid excessive input signal amplitudes This is particularly valid when measuring on high impedance circuitry and when using 1MQ input impedance Under these conditions the cables easily pick up noise External attenuation and the internal 10x attenuator reduce the signal amplitude includ ing the noise while the internal sensitivity control in the counter reduces the counter s sensitivity including sensitivity to noise Re duce excessive signal amplitudes with the 10x attenuator or with an external coaxial attenuator or a 10 1 probe How to use Trigger Level Setting For most frequency measurements the optimal triggering is obtained by positioning the mean trigge
78. he input signal meets the stop trigger conditions That hap pens directly after the following events 5 4 The Measurement Process The set measurement time has expired ap plies to Frequency and Period Aver age measurements only The input signal fulfils the stop trigger conditions normally when it passes the trigger window the second time Resolution as Function of Measurement Time The quantization error and the number of dig its on the display mainly define the resolution of the counter that is the least significant digit displayed As explained on page 4 10 under Reciprocal Counting the calculated frequency fis fet tz while the relative rms quantization error Eq 100ps tg The counter truncates irrelevant digits so that the rms quantization resolution cannot change the LSD least significant digit more than 5 units This occurs when the displayed value is 99999999 and the quantization error is worst case The best case is when the displayed value is 10000000 Then the quantization res olution corresponds to 0 5 LSD units 1 unit in 99999999 1E8 i means 10 times more relative resolution than 1 unit in 10000000 1E7 despite the same number of digits A gradual increase of the measurement time reduces the instability in the LSD caused by the quantization uncertainty At a specific measurement time setting the counter is justi fied to display one more digit That one addi ti
79. ic distor tion see Fig 3 17 can be measured correctly by shifting the trigger point to a suitable level or by using continuously variable sensitivity see Fig 3 16 You can also use Trigger Hold Off in case the measurement result is not in line with your expectations Goon Fig 3 16 Variable sensitivity Fig 3 17 Harmonic distortion 3 8 How to Reduce or Ignore Noise and Interference Chapter 4 Measuring Functions Measuring Functions Introduction to This Chapter This chapter describes the different measuring functions of the counter They have been grouped as follows Frequency measurements Frequency Period Ratio Burst frequency and PRF FM AM Time measurements Time interval Pulse width Duty factor Rise Fall time Phase measurements Voltage measurements Vmax VIN Vpp 4 2 Selecting Function Selecting Function See also the front panel layout on page 2 3 to find the keys mentioned in this section to gether with short descriptions Press MEAS FUNC to open the main menu for selecting measuring function The two ba sic methods to select a specific function and its subsequent parameters are described on page 2 6 MEAS AUTO EXIT ok Measuring Functions Frequency Measurements FREQ A B The counter mea
80. ignal ex ceeds the dynamic input voltage range 5 V or else when attenuation can reduce the influence of noise and interference See the section deal ing with these matters at the end of this chap ter CROSSPOINT MEASURING MICRO COUPL CONV FILTER SWITCH COMP LOGIC CONTROLLER B COUPL IMP FILTER COMP CONV TRIG LVLA TRIG LVL B35 Fig 3 1 Block diagram of the signal conditioning 3 2 Input Amplifier Coupling Switch between AC coupling and DC cou pling by toggling the softkey AC DC DC Coupling 5V AAAA AC Coupling AAAA Fig 3 3 AC coupling a symmetrical sig nal Use the AC coupling feature to eliminate un wanted DC signal components Always use AC coupling when the AC signal is superim posed on a DC voltage that is higher than the trigger level setting range However we rec ommend AC coupling in many other measure ment situations as well When you measure symmetrical signals such as sine and square triangle waves AC cou pling filters out all DC components This means that a 0 V trigger level is always cen tered around the middle of the signal where triggering is most stable Input Signal Conditioning NOTE For explanation of the hysteresis band see page 4 3 i Fig 3 5 No triggering due to AC coupling
81. ilter Analog LP Digital LP 100 kHz Digital LP Freq Off Off 100 kHz Fig 2 8 Selecting analog or digital filter m Input B The settings under Input B are equal to those under Input A Description of Keys 2 9 Using the Controls m Settings Arm Frequency A DERE Frequency A Meas 10 000 040 61 mz 50 000 001 76 mz Settings vettings Arm Burst Trigger Timebase Start Start firm Stop Stop MeasTime Hold Off Stat Ref Misc WE Slope delay Chan Slope 10 ms f tnt Off I 200 us Off T Fig 2 9 The main settings menu Fig 2 12 Setting arming conditions This key accesses a host of menus that affect the measurement The figure above is valid af ter changing the default measuring time to 10 ms Meas Time Frequency fi Meas 50 000 001 76 mz Settings MeasTime ETT ms vs 5 Fig 2 10 Submenu for entering measur ing time This value input menu is active if you select a frequency function Longer measuring time means fewer measurements per second and gives higher resolution Burst Frequency A Meas 90 000 001 76 mz Settings Burst Frequency EMBE Start delay Meas time Limit 200 us 200 us 200 us 300 MHz Fig 2 11 Entering burst parameters This settings menu is active if the selected measurement function is BURST a special case of FREQUENCY and facilitates mea surements on pulse modulated signals Both the carrier frequency and the modulating
82. imum number of 4 4 RATIO A B B A C A C B cycles will be 3 x prescaling factor The 3 GHz option for example has a prescaling factor of 16 and requires at least 48 cycles in each burst The minimum burst duration is 40 ns below and 80 ns above 160 MHz Triggering Bursts with a PRF above 50 Hz can be mea sured with auto triggering on The out of sync error described under heading Possible errors on page 4 6may occur more frequently when using Auto Trigger When PRF is below 50 Hz and when the gap between the bursts is very small use manual triggering Always try using AUTOSET first Then the Auto Trigger and the Auto Sync functions in combination will give satisfactory results without further tweaking in most cases Some times switching from AUTO to MANual trig gering in the INPUT A B menus is enough to get stable readings The continually calculated trigger levels will then be fixed Input C has always automatic triggering and AUTOSET only affects the burst synchroni zation Cw MU NIU mm Burst W WW Jil Wi II Signal ili V WT EMIL NES qu c Fig 4 2 Burst signal Burst Measurements using Manual Presetting You can measure the frequency on Input A and Input B to 300 MHz and on Input C with limited specifications to the upper frequency limit of the prescaler with the internally syn chronized BURST function as follows Select Freq Burst under the
83. ing by keying in the fol lowing sequence SETTINGS Arm gt Start Chan OFF gt E Press EXIT OK twice The counter does not measure Apply one single pulse to Ext Arm Input The counter measures once and shows 10 MHz on the display Measuring Functions Connect a 10 MHz sine wave signal with approx 1 Vrms amplitude into 50 Q via a power splitter to Input A and Input B e g from 10 MHz Out on the rear panel Use equal cable lengths from the power splitter to the inputs Recall the DEFAULT settings Select the following settings for the timer counter via INPUT A and INPUT B 50 Q impedance for A and B MANual trigger POS slope Check that the timer counter performs the correct measurement by displaying the re sult as shown under the Display column in Table 7 7 Select function via MEAS FUNC 7 10 Measuring Functions Check of HOLD OFF Function Recall the DEFAULT settings Select Period Single A Select the following common timer counter settings for both Input A and Input B via the hard menu keys INPUT A and INPUT B 50 Q impedance DC coupling MANual trigger X1 attenuation Press SETTINGS and activate Hold Off Select Hold Off On and set the Trigger Hold Off time to the minimum value 20 ns Connect the rear panel output marked 10 MHz OUT to Input A Increase the Trigger Hold Off time in steps by means of the
84. ingly To check the accuracy of the oscillator you must have a calibrated reference signal that is at least five times more stable than the oscilla tor that you are testing See Table 7 6 and the list of test equipment on page 7 2 If you use a non 10 MHz reference you can use the math ematics in the timer counter to multiply the reading Recall the DEFAULT settings Connect the reference to input A Check the readout against the accuracy re quirements of your application W Acceptance Test Table 7 6 can serve as an acceptance test and gives a worst case figure after 30 minutes warm up time All deviations that can occur in a year are added together Oscillator Frequency Readout Suitable Reference P F PM6690 1 Standard 10 00000000 MHz 150 Hz 908 PM6690 5 OCXO 10 00000000 MHz 1 Hz 909 PM6690 6 OCXO 10 00000000 MHz 0 25 Hz 909 Table 7 6 Acceptance test for oscillators 7 8 Short Form Specification Test Resolution Test Connect the pulse generator to a power splitter Connect one side of the power splitter to Input A on the counter using a coaxial ca ble Connect the other side of the power split ter to Input B on the counter Settings for the pulse generator Amplitude 2 Vpp high level 2 V and low level 0 V Period approx 1 us Duration approx 50 ns Rise time 2 ns Restore the timer counter s def
85. io Aux Parameters Freq 1 Freq 2 Time Interval A to B B to A Ato A BtoB Range normal calculation 0 ns to 108 S Range smart calculation 108 to 10 s Resolution Single Shot 100 ps Input Frequency Up to 160 MHz Min Pulse Width 1 6 ns Smart Calculation Smart Time Int w 4 time stamps 2 consecutive Trig A plus 2 consecutive Trig B to determine sign A before B or A after B Specifications m Display Main Parameter Time interval Aux Parameters None Pulse Width A B Range 2 5 ns 10 S Input Frequency Up to 200 MHz Modes Pos pulse width or neg pulse width m Display Main Parameter Pulse width Aux Parameters Vmax Vmin Vp p Rise and Fall Time A B Range 1 5 ns 1000 s Input Frequency Up to 160 MHz square wave Default 10 and 90 Manually adjustable Trigger Levels Min Pulse Width 1 6 ns Modes Rise or fall time Min Amplitude 100 mVp p m Display Rise or fall time Slew rate Vmax Vmin Main Parameter Aux Parameters Measurement Functions 8 3 Specifications Phase A Rel B B Rel A Range 180 to 360 Resolution 0 001 to 10 kHz 0 01 to 1 MHz 0 1 to 10 MHz 1 gt 10 MHz Resolution can be im proved by averaging Statistics Input Frequency Up to 160 MHz Min Pulse Width 1 6 ns m Display Main Parameter Phase Aux Parameters Freq prim channel VANNB in dB Duty Factor A B Range 0 000001 to 0 999999
86. l Input A Input B INPUT A DC 50 Q 950 mV 50 mV AC 450 mV 450 mV 10X 0 45 V 0 45 V 1 MQ gt 0 45 V lt 0 45 V Table 7 5 Input controls check Short Form Specification Test 7 7 Performance Check Input Controls Recall the DEFAULT settings Connect the LF synthesizer to Input A Use the same settings as in the previous test Press INPUT A and select DC and 50 Q Press EXIT OK Check the Vmax and Vmin voltage levels on the display according to the first row in Table 7 5 Perform the rest of the settings in se quence and read the corresponding Vmax and Vmin values Remember that these val ues are approximate and serve only as in dicators of state changes Connect the generator to Input B Press MEAS FUNC Freq Freq A gt B Press INPUT B and select DC and 50 Q Press EXIT OK Check the Vmax and Vmin voltage levels on the display according to the first row in Table 7 5 Perform the rest of the settings in se quence and read the corresponding Vmax and Vmin values for Input B according to Table 7 5 Reference Oscillators X tal oscillators are affected by a number of external conditions like ambient temperature and supply voltage Aging is also an important factor Therefore it is hard to give limits for the allowed frequency deviation The user himself must decide the limits depending on his application and recalibrate the oscillator accord
87. lating Frequency The easiest way to measure the modulating frequency is after demodulation for instance by means of a so called RF detector probe also known as a demodulator probe e g Pomona type 5815 used with AC coupling of the input channel If no suitable demodulator is available use the Freq Burst function to measure the modulation frequency in the same way as when measuring Burst PRF Sync delay Measured cycles Fig 4 9 Measuring the modulating fre quency Press MEAS FUNC and select Freq Burst A Press SETTINGS Burst Meas Time and enter a measurement time that is approximately 25 of the modulating period Press Sync Delay and enter a value that is approximately 75 of the modulating period See Fig 4 3 Press INPUT A and turn on Manual trig ger Press Trig and enter a trigger level that makes the counter trigger according to Fig 4 9 Even though the main frequency reading may now be unstable the PRF value on the display will represent the modulating frequency Measuring Functions Theory of Measurement Reciprocal Counting Simple frequency counters count the number of input cycles during a preset gate time for instance one second This leads to a 1 input cycle count error that at least for low fre quency measurements is a major contribution to uncertainty However the counters described here use a high resolution reciprocal cou
88. led from internal non volatile memory 10 can be user protected Display Type amp Use Graphics screen for menu control numerical readout 14 digits and status info Resolution 320 x 97 pixels Technology Monochrome LCD with white LED backlight GPIB Interface Programmable Functions All front panel accessible functions 8 8 Auxiliary Functions Compatibility IEEE 488 2 1987 SCPI 1999 Modes Native mode Agilent compatible mode Agilent Compatibility HP 53131 132 181 com mands are emulated Code and response for mat is compatible No tim ing compatibility No reso lution compatibility Interface Func tions SH1 AH1 T6 L4 SR1 RL1 DC1 DT1 E2 Max Meas Rate Via GPIB 2000 readings s block 350 readings s individual To Internal Memory 250 k readings s Internal Memory Size Up to 750 k readings Data Output ASCII IEEE double preci sion floating point USB Interface Version 2 0 12 Mb s Protocol USBTMC USB488 TimeView This software package is intended for ad vanced Modulation Domain analysis and runs on any 32 bit Windows system m Data Capture Modes amp Measurement Rate Effective rate depends on measurement func tion and internal data format Free running Measurement 250 k readings s Repetitive Sampling Continuous Single Period Waveform Capture Data Analysis Features Up to 100 Msa s equiv sample rate 10 ns be tween samples Ye
89. lly the best choice when making time measure ments Choose Man Trig and press AUTOSET once DC coupling 1x Attenuation Selected automatically if AUTOSET was used before to set the trigger levels High signal level Steep signal edges Even though the input amplifiers have high sensitivity the hysteresis band has a finite value that would introduce a small timing er ror for signals with different rise and fall times for instance asymmetrical pulse signals like the one in Fig 4 14 This timing error is taken care of by using hysteresis compensa Introduction 4 13 Measuring Functions tion that virtually moves the trigger points by half the hysteresis band Time Interval All time interval functions can be found under the function menu Time The toggling SLOPE keys marked with a positive I or negative L edge symbol un der the menus INPUT A B decide which edge of the signal will start resp stop the measure ment Time Interval A to B The counter measures the time between a start condition on input A and a stop condition on input B Time Interval B to A The counter measures the time between a start condition on input B and a stop condition on input A Time Interval A to A B to B When the same common signal source sup plies both start and stop trigger events con nect the signal to either input A or input B These functions can be used for measuring rise and fall times betwe
90. max 2 500 0 040 V Repeat the measurement with inverted po larity Press INPUT A and select 10x Press EXIT OK CAUTION Before the next step make sure the input impedance is still 1 MQ Applying more than 12 V without proper current limiting may cause extensive damage to the main PCB if the impedance is set to 50 Q Change the DC level to 50 00 V The display should now indicate VMIN 50 00 0 65 V and VMAX 50 00 0 65 V Repeat the measurement with inverted po larity Disconnect the DC voltage from Chan nel A Remove the external low pass filter Press INPUT A and select 1x 7 6 Short Form Specification Test Press EXIT OK Connect a sinusoidal signal to Input A with an amplitude of 4 000 Vpp and a fre quency of 100 kHz The display should now indicate 4 000 0 150 Vpp Press INPUT A and select 10x Press EXIT OK Change the amplitude to 18 00 Vpp The display should now indicate 18 00 0 84 Vpp Disconnect the signal from Channel A Press MEAS FUNC Volt Vpp gt B Press INPUT B and select DC coupling Do not apply an input signal to Input B yet Press EXIT OK The display should now indicate disregard the main parameter V pp VMiN 0 0 015 V and Vmax 0 0 015 V Proceed by repeating the measurements for Input B as described above for In put A Per
91. nage without using the arming function at all Often the counter can automatically synchronize the measure ment start to the triggering of the first pulse The conditions for success are that the PRF is not too high preferably below 50 Hz and cer tainly not above 150 Hz The duration of a pulse burst between first and last pulse should be substantially less than the distance to the next burst and the number of pulses in the burst should be more than 100 to avoid oc casional miscounts Do the following steps to perform auto syn chronization without arming Connect the burst signal to input A Adjust the manual sensitivity and trigger level until the burst signal triggers the counter correctly Use the MEAS FUNC key to select Pulse Width A Use Pacing Time to select a value that approaches the time between the bursts Absolute synchronization will not be guaran teed in this way but there is a high probability that auto synchronization will work anyway However occasional erroneous values will be displayed To achieve guaranteed synchroni zation use the Start Arming function 5 10 Arming Examples m B Synchronization Using Start Arming The SYNC signal can be directly used to arm the measurement This requires that the lead ing edge of the SYNC signal occurs more than 5 nanoseconds before the leading edge of the first pulse in the burst See Fig 5 9 Sync E FE Start Arming i Input A f i
92. nd 2 Arming Examples 5 11 Measurement Control 3 Measuring the Time Between Burst Pulse 1 and 4 In the previous examples the synchronization task has been to identify the start of a mea surement and to perform a single shot time in terval measurement Now we will complicate the picture even more In our next example we will not only arm the start but also the stop of a measurement We will measure the time be tween the first and the fourth pulse in the pulse burst We still have the SYNC signal available see Fig 5 13 Sync E g Input A Fig 5 13 Measuring a time interval inside a burst The measurement function is not Pulse Width A but Time Interval A to A where the set tings for input B are used for controlling the stop conditions The desired start and stop trigger points are marked in the preceding il lustration Our task is now to arm both the start and the stop of this measurement The start arming is already described in example 1 i e synchronize measurement start to the leading edge of the first pulse The challenge is to synchronize the stop of the measurement i e to arm the stop If we do nothing the time interval measured will be the time between the first and the second pulse We must thus delay the stop This can be done in different ways W A Using Trigger Hold Off to Delay the Stop a Certain Time Trigger Hold Off is used to inhibit stop trig gering during a pre
93. nel A and B Let us look deeper into the restrictions and possibilities of using phase measurements Inaccuracy The measurement errors are of two kinds Random errors Systematic errors The random errors consist of resolution quantization and noise trigger error Systematic errors consist of inter channel de lay difference and trigger level timing er rors Systematic errors are constant for a given set of input signals and in general you can compensate for them in the controller GPIB systems or locally via the MATH LIM menu manual operation after making cali bration measurements See Methods of Com pensation on page 4 20 4 18 Possible Errors m Random Errors The phase quantization error algorithm is 100 ps x FREQ x 360 For example the quantization error for a 1 MHz input signal is thus 100 ps x 1x10 x 360 0 04 The trigger noise error consists of start and stop trigger errors that should be added For sinusoidal input signals each error is 360 27 x54 ratio Let s use the example above and add some noise so that the S N ratio will be 40 dB This corresponds to an amplitude ratio of 100 times and power ratio of 10000 times Then the trigger noise will contribute to the random er ror with 360 0 6 2n x100 The sum of random errors should not be added linearly but in an RMS way because of their random nature Let s do so for our exam ples ab
94. ng functions will be performed Set Meas Time to 200 ms Switch off Hold Off Set HOLD RUN to RUN Switch off MATH LIM Switch off Analog and Digital Filters Set Timebase Ref to Internal Switch off Arming m Default Settings An even more comprehensive preset function can be performed by recalling the factory de fault settings See page 2 13 Move Cursor There are four arrow keys for moving the cur sor normally marked by text inversion around the menu trees in two dimensions Display Contrast When no cursor is visible no active menu se lected the UP DOWN arrows are used for adjusting the LCD display contrast ratio Enter The key marked ENTER enables you to con firm a choice without leaving your menu posi tion Save amp Exit This hard key is marked EXIT OK You will confirm your selection by depressing it and at the same time you will leave the current menu level for the next higher level Don t Save amp Exit This hard key is marked CANCEL By de pressing it you will enter the preceding menu level without confirming any selections made at the current level If the instrument is in REMOTE mode this key is used for returning to LOCAL mode unless LOCAL LOCKOUT has been pro grammed Presentation Modes m VALUE Frequency fi Meas 50 000 001 76 mz Umax 1 4624U Umin 2 5284U Up p 3 9908 U Fig 2 2 Main and aux parameters Value mode gives sin
95. nput B These values can be manually adjusted between 50 and 100 on Input A and between 0 and 50 on Input B The signal however is only ap plied to one channel Before each frequency measurement the coun ter repeats this signal probing to identify new MIN MAX values A prerequisite to enable AUTO triggering is therefore that the input signal is repetitive i e 2100 Hz default Another condition is that the signal amplitude does not change significantly after the mea surement has started NOTE AUTO trigger limits the maximum mea suring rate when an automatic test sys tem makes many measurements per second Here you can increase the measuring rate by switching off this probing if the signal amplitude is con stant One single command and the AUTO trigger function determines the trigger level once and enters it as a fixed trigger level m Manual Trigger Switching to Man Trig also means Narrow Hysteresis at the last Auto Level Pressing AUTOSET once starts a single automatic trigger level calculation 4uto Once This cal culated value 50 of the peak to peak am plitude will be the new fixed trigger level from which you can make manual adjustments if need be m Harmonic Distortion As rule of thumb stable readings are free from noise or interference However stable readings are not necessarily correct harmonic distortion can cause errone ous yet stable readings Sine wave signals with much harmon
96. nt MS 30Vms IMN MAX 30dBm JJ STANDBY LED STANDBY ON MATH LIMIT USER OPT The LED lights up when the counter is in STANDBY mode indicating that power is still applied to an internal optional OCXO if one has been installed 2 2 Basic Controls Toggling secondary power switch Pressing this button in standby mode turns the counter ON and restores the settings as they were at power down Menu for selecting one of a set of for mulas for modifying the measurement result Three con stants can be en tered from the keyboard Numerical limits can also be en tered for status re porting and recording Controls the follow ing items 1 Settings memory 2 Calibration 3 Interface 4 Self test 5 Blank digits 6 About STAT PLOT VALUE Enters the nor mal numerical Enters one of three statistics presentation presentation modes mode with one Switching be main parameter tween the modes and a number of is done by auxiliary parame toggling the key ters Using the Controls MEAS FUNC AUTO SET Menu tree for Adjusts input selecting mea trigger voltages surement func tion automatically to the optimum lev els for the cho You can use the sen measure seven softkeys ment function below the dis play for confir Double click for mation default settings CURSOR CONTROL The cursor position marked by text inversion on the display can be moved in four directions
97. nting tech nique synchronizing the measurement start with the input signal In this way an exact number of integral input cycles will be counted thereby omitting the 1 input cycle error Set Measuring Time t Actual Gtit Time Fig 4 10 Synchronization of a measure ment After the start of the set measurement time the counter synchronizes the beginning of the actual gate time with the first trigger event t1 of the input signal See also Fig 4 10 In the same way the counter synchronizes the stop of the actual gate time with the input sig nal after the set measurement time has elapsed The multi register counting technique allows you to simultaneously measure the ac Theory of Measurement 4 9 Measuring Functions tual gate time tg and the number of cycles n that occurred during this gate time Thereafter the counter calculates the fre quency according to Mr Hertz s definition fat be The 90 measures the gate time tg with a res olution of 100 ps independent of the mea sured frequency Consequently the use of prescalers does not influence the quantization error Therefore the re ative quantization error is 100 ps tg For a 1 second measurement time this value is 100 ps ls 2100x107 21x10 Except for very low frequencies tg and the set measurement time are nearly identical Sample Hold If the input signal disappears during
98. ntionally left blank 6 8 Limits and Graphics Chapter 7 Performance Check Performance Check General Information WARNING Before turning on the in strument ensure that it has been installed in accordance with the In stallation Instructions outlined in Chapter 1 of the User s Manual This performance procedure is intended for checking the instrument s specification incoming inspection to determine the ac ceptability of newly purchased instruments and recently recalibrated instruments checking the necessity of recalibration af ter the specified recalibration intervals NOTE The procedure does not check every facet of the instrument s calibration rather it is concerned primarily with those parts of the instrument which are essential for determining the function of the instrument It is not necessary to remove the instrument cover to perform this procedure Preparations Power up your instrument at least 30 minutes before check ing to let it reach normal oper ating temperature Failure to do so may result in certain test steps not meeting equipment specifications Test Equipment Type of Equipment Required Specifications 10 MHz 1 10 e g 908 for calibrating the standard oscillator Reference Oscillator 10 MHz 1 10 e g 909 for calibrating PM6690 5 amp PM6690 6 Voltage Calibrator DC 50 V to 50 V e g 5500 for calibrating the built in
99. o select the part of the burst that is of interest Use the same test setup as in the preceding ex ample Then proceed as follows Press SETTINGS Arm and select Stop Chan E and negative Stop Slope Measure 4 Profiling Profiling means measuring frequency versus time Examples are measuring warm up drift in signal sources over hours measuring the linearity of a frequency sweep during seconds VCO switching characteristics during milli seconds or the frequency changes inside a chirp radar pulse during microseconds These counters can handle many profiling measurement situations with some limitations Profiling can theoretically be done manually i e by reading individual measurement re sults and plotting in a graph However to avoid getting bored long before reaching your 800th or so measurement result you must use some computing power and a bus interface In profiling applications the counter acts as a fast high resolution sampling front end stor ing results in its internal memory These re sults are later transferred to the controller for analysis and graphical presentation The TimeView software package greatly simpli fies profiling Measurement Control You must distinguish between two different types of measurements called free running and repetitive sampling m Free Running Measurements Free running measurements are performed over a longer period e g to measure the sta bility ov
100. of input signal Minimum hyster esis window if arming on A or B is activated Freq Range gt 1 Hz default 100 Hz Analog Noise Reduction Filter Digital LP Filter Nom 100 kHz RC type 1 Hz 50 MHz using trig ger hold off Trigger Indicators LED Max Voltage w o Damage 1 MQ 350 V DC ACpk DC to 440 Hz falling to 12 VRMS x1 and 120 VRMS x10 1 MHz 50 Q 12 VRMS Input C PM6690 6xx 100 MHz 3 0 GHz Prescaler Factor 16 Freq Range Operating Input Voltage Range 100 300 MHz 20 mVrms 12 Vrms 0 3 2 5 GHz 10 mVrms 12 Vrms 2 5 2 7 GHz 20 mVrms 12 Vrms 2 7 3 0 GHz 40 mVrms 12 Vrms Amplitude Modulation DC 0 1 MHz Modulation Frequency Up to 94 depth 0 1 6 MHz Modulation Frequency Up to 85 depth Min signal must exceed min oper input voltage Impedance 50 Q nom AC coupled VSWR lt 2 5 1 8 6 Input and Output Specifications Max Voltage w o Damage Connector 12 Vrms PIN diode prot Type N female Input C PM6690 7xx Freq Range Prescaler Factor Operating input voltage range 0 3 0 5 GHz 0 5 3 0 GHz 3 0 4 5 GHz 4 5 6 0 GHz 6 0 8 0 GHz Amplitude Modulation DC 0 1 MHz Modulation Frequency 0 1 6 MHz Modulation Frequency Impedance Max Voltage w o Damage Connector 300 MHz 8 GHz 256 20 mVrms 7 Vrms 10 mVrms 7 Vrms 20 mVrms 7 Vrms 40 mVrms 7 Vrms 80 mVrms 7 Vrms Up to 9496
101. of sam ples measurements taken at short intervals The fundamental idea is to eliminate the influ ence of long term drift due to aging tempera ture or wander This is done by making con secutive comparisons of adjacent samples The Standard Deviation which is probably a more familiar statistic considers the effects of all types of deviation as all samples in the population are compared with the total mean value As you can see both the Allan Deviation and the Standard Deviation are expressed in the same units as the main parameter e g Hz or s Selecting Sampling Parameters Press SETTINGS Stat Press No of samples and enter a new value by means of the numerical keys or the UP DOWN arrow keys if you want to change the default value of 100 Proceed in the same way for No of bins if you want to present the measurement re sults graphically in a histogram Note that the six statistic mea sures are calculated and dis played simultaneously only in the Statistics 6 3 Process non graphic presentation mode under STAT PLOT Use the same key for toggling between the three modes Nu merical Histogram Trend Press Pacing time and enter a new value if you want to change the default value 20 ms The range is 2 us 1000 s The pacing parameter sets the sampling inter val Activate the set pacing time by pressing Pacing Off The status is changed to Pacing On Status Pacing Off m
102. of signal with low duty cycle Filter If you cannot obtain a stable reading the sig nal to noise ratio often designated S N or SNR might be too low probably less than 6 to 10 dB Then you should use a filter Certain conditions call for special solutions like highpass bandpass or notch filters but usu ally the unwanted noise signals have higher frequency than the signal you are interested in In that case you can utilize the built in lowpass filters There are both analog and dig ital filters and they can also work together Fig 3 4 Missing trigger events due to AC coupling of signal with varying duty cycle Signals with changing duty cycle or with a very low or high duty cycle do require DC coupling Fig 3 4shows how pulses can be missed while Fig 3 5shows that triggering does not occur at all because the signal ampli tude and the hysteresis band are not centered Frequency A Meas 50 000 001 76 mz Input A Filter Analog LP Digital LP 100 kHz Digital LP Freq Off Off 100 kHz Fig 3 6 The menu choices after selecting FILTER m Analog Lowpass Filter The counter has analog LP filters of RC type one in each of the channels A and B with a cutoff frequency of approximately 100 kHz and a signal rejection of 20 dB at 1 MHz Accurate frequency measurements of noisy LF signals up to 200 kHz can be made when the noise components have significantly Input Amplifier 3 3 Input
103. ollowing table Trigger level timing error The trigger level timing error is depending on two factors The actual trigger point is not exactly Zero due to trigger level DAC uncertainty and comparator offset error The two signals have different slew rates at the zero crossing Every counter has input hysteresis This is necessary to prevent noise to cause erroneous input triggering The width of the hysteresis band determines the maximum sensitivity of the counter It is approximately 30 mV so when you set a trigger level of 0 V the actual trigger point would normally be 15 mV and the recovery point 15 mV This kind of tim ing error is cancelled out by using hysteresis compensation Hysteresis compensation means that the mi crocomputer can offset the trigger level so that actual triggering after offset equals the set trigger level before offset This general hys teresis compensation is active in phase as well as in time interval and rise fall time measure ments There is a certain residual uncertainty of a few mV and there is also a certain tem perature drift of the trigger point The nominal trigger point is 0 V with an un certainty of x 10 mV Possible Errors 4 19 Measuring Functions A sine wave expressed as V t 2 Vp x sin 27ft has a slew rate of t V x 2nfclose to the zero crosssing That gives us the systematic time error when crossing 10 mV instead of crossing 0 mV 10mV
104. on See also timebase specifications on page 8 14 8 12 Calibration General Specifications Environmental Data Class Operat Temp Storage Temp Humidity Max Altitude Vibration Shock Transit Drop Test Reliability Safety EMC MIL PRF 28800F Class 3 0 C to 50 C 40 C to 71 C 5 95 10 30 C 5 75 30 40 C 5 45 40 50 C 4600 m Random and sinusoidal per MIL PRF 28800F Class 3 Half sine 30G per MIL PRF 28800F bench handling Transport box tested ac cording to UN D 1400 drop test program 1 Heavy duty transport case and soft carrying case tested according to MIL PRF 28800F MTBF 30000 h calculated Designed and tested for Measurement Category I Pollution Degree 2 in ac cordance with EN IEC 61010 1 2001 and CAN CSA C22 2 No 61010 1 04 incl approval EN 61326 1997 A1 1998 increased test levels per EN 50082 2 Group 1 Class B CE Power Requirements Line Voltage Power Consumption 90 265 VRMs 45 440 Hz 40 W Specifications Dimensions amp Weight Width Height Depth Weight 75 x 19 210 mm 2E 90 mm 395 mm Net 2 7 kg 5 8 Ib Shipping 3 5 kg 7 5 Ib Ordering Information Basic Model PM6690 300 MHz 100 ps Included with In strument HF Input Options PM6690 6 PM6690 7 Timebase Options PM6690 5 PM6690 6 Optional Acces sories TimeView 90 PM961 1 90 PM9622 PM9627
105. onal digit suddenly gives ten times more dis play resolution but not a ten times less quantization uncertainty Consequently a measurement time that gives just one more display digit shows more visual uncertainty in the last digit For a stable LSD readout the maximum mea surement time selected should be one that still gives the required number of digits Such opti mization of the measurement time enables the total resolution to be equal to the quantization resolution Measurement Time and Rates The set measurement time decides the length of a measurement if Frequency or Period Average is selected This is important to know when you want to make fast measurements for example when you are using the statistics features or when you are collecting data over the GPIB bus The so called dead time that is the time be tween the stop of one measurement and the start of the next one in the course of a block measurement can be below 2 us Measurement Control A block is a collection of consecutive mea surements the results of which are stored in local memory for statistics or plotting pur poses STAT PLOT menu or for later trans fer to a controller over one of the data com munication links GPIB USB or ETHERNET Additional controls over start and stop of measurements Free running measurements may be easy to understand but measurements can get more complex Besides input signal triggering the start of a
106. ove Random error J quant err start trg err stop trg err The total random errors are thus 40 047 0 6 0 6 0 85 single shot What about random errors caused by internal amplifier noise Internal noise contribution is normally negligible The phase error caused by noise on the signal whether internal or ex ternal is 360 2n x K ratio For an input signal of 250 mVrms and the typi cal internal noise figure of 250 uVrms gives us a S N ratio of a minimum of 60 dB 1000 times This gives us a worst case error of 0 06 Increasing the input signal to 1 5 Vims decreases the error to 0 01 Another way to decrease random errors is to use the statistics features of the instrument and calculate the mean value from a number of samples m Systematic Errors in Phase Measurements 160 MHz 28 8 100 MHz 18 0 10 MHz 1 8 1 MHz 0 18 100 kHz 0 018 10 kHz and below 0 002 Table 4 2 Phase difference caused by inter channel propagation delay difference Systematic errors consist of 3 elements Measuring Functions nter channel propagation delay difference Trigger level timing errors start and stop due to trigger level uncertainty The inter channel propagation delay differ ence is typically 500 ps at identical trigger conditions in both input channels Therefore the corresponding Phase difference is 0 5 ns x360 x FREQ See the f
107. ow pass noise suppression filter Digital low pass filter Trigger Hold Off To make reliable measurements possible on very noisy signals you may use several of the above features simultaneously Optimizing the input amplitude and the trigger level using the attenuator and the trigger con trol is independent of input frequency and useful over the entire frequency range LP fil ters on the other hand function selectively over a limited frequency range Trigger Hysteresis The signal needs to cross the 20 mV input hysteresis band before triggering occurs This hysteresis prevents the input from self oscil lating and reduces its sensitivity to noise Other names for trigger hysteresis are trigger sensitivity and noise immunity They ex plain the various characteristics of the hyster esis Fig 3 12 Erroneous counts when noise passes hysteresis window Fig 3 10 and Fig 3 12 show how spurious signals can cause the input signal to cross the 3 6 How to Reduce or Ignore Noise and Interference trigger or hysteresis window more than once per input cycle and give erroneous counts Fig 3 13 Trigger uncertainty due to noise Fig 3 13 shows that less noise still affects the trigger point by advancing or delaying it but it does not cause erroneous counts This trig ger uncertainty is of particular importance when measuring low frequency signals since the si
108. r level at mid amplitude using either a narrow or a wide hysteresis band de pending on the signal characteristics Fig 3 15 Timing error due to slew rate When measuring LF sine wave signals with little noise you may want to measure with a How to Reduce or Ignore Noise and Interference 3 7 Input Signal Conditioning high sensitivity narrow hysteresis band to re duce the trigger uncertainty Triggering at or close to the middle of the signal leads to the smallest trigger timing error since the signal slope is steepest at the sine wave center see Fig 3 15 When you have to avoid erroneous counts due to noisy signals see Fig 3 12 expanding the hysteresis window gives the best result if you still center the window around the middle of the input signal The input signal excursions beyond the hysteresis band should be equally large m Auto Trigger For normal frequency measurements i e without arming the Auto Trigger function changes to Auto Wide Hysteresis thus wid ening the hysteresis window to lie between 70 and 30 of the peak to peak ampli tude This is done with a successive approxi mation method by which the signal s MIN and MAX levels are identified i e the levels where triggering just stops After this MIN MAX probing the counter sets the trig ger levels to the calculated values The default relative trigger levels are indicated by 70 on Input A and 30 on I
109. rements you must select measuring time in accordance with what you want to obtain Jitter or very short time cycle to cycle varia tions require that the samples be taken as Sin gle measurements If average is used Freq or Period Average only the samples used for the statistical cal culations are already averaged unless the set measuring time is less than the period time of the input signal up to 160 MHz Above this frequency prescaling by two is introduced anyhow and as a consequence a certain amount of averaging This can be a great ad vantage when you measure medium or long time instabilities Here averaging works as a smoothing function eliminating the effect of jitter The signal in Fig 6 1contains a slower varia tion as well as jitter When measuring jitter you should use a limited number of samples so that the slow variation does not become no ticeable or alternatively use the dedicated sta tistic measure for this kind of measurement the Allan deviation To measure the slower variation you calculate Max Min or Mean on a long series of aver aged samples Here averaging eliminates the jitter in each sample and the long measuring time and large number of samples means that the measurement can record very slow varia tions The maximum pacing time equals the maximum measuring time for each sample and is 1000 s and the maximum number of samples is 2 10 which in effect means that a single data capture coul
110. s from LF to 250 kHz repetition rate Yes Measurement data vs time Cursor measurements Distribution histogram FFT graph w Hamming Hanning and other rele vant filters Smoothing Zoom Setup measurement data archive and printing Zero dead time ADEV and MADEV vs t Specifications Auxiliary Functions 8 9 Specifications Measurement Uncertainties Random Uncertainties 10 m Quantization Error Eq Eq 100 ps rms m Start Stop Trigger Error Ess 2 2 Ess Ekose Ehuer 5 1 Wo LL oc uico noise input noise signal ad V s inp sign slew rate A at trig point noise Ej Single Period Jitter rms s 500 uVrms internal noise 200 uVrms typical The rms noise of the applied signal Vnoise input Vnoise signal Systematic Uncertainties m Trigger Level Timing Error Et Time Interval Rise Fall Time Pulse Width Duty Factor Phase attenuator setting x1 Eq TLU 4x Hyst 06 OGY 1s where Sx Slew rate at start trigger point V s Sy Slew rate at stop trigger point V s TLU Trigger level uncertainty V Hyst Hysteresis window V Hyst 30 mV 1 of trig lvl DC to 1 kHz for Pulse Width amp Duty Factor Hyst 6mV 1 of trig lvl DC tol kHz for other measurement functions 8 10 Measurement Uncertainties m Timebase Error TBE TBE is the relative error of the timebase oscil lator dimensionless and depends on
111. s because the period of a cyclic signal has the reciprocal value of the frequency 7 In practice there are two minor differences 1 The counter calculates FREQUENCY always AVG as number of cycles actual gate time while it calculates PERIOD AVG as actual gate time number of cycles 2 In the PERIOD SINGLE mode the coun ter uses no prescaler All other functions and features as described earlier under Frequency apply to Period measurements Measuring Functions Time Measurements Introduction Measuring the time between a start and a stop condition on two separate channels is the basis for all time interval measurements In addition to the fundamental function Time Interval A to B the counters also offer other channel combinations and derived functions like Pulse Width and Rise Fall Time Hysteresis band SENS Trigger level offset ru v Trigger points Reset points Fig 4 14 Time is measured be tween the trigger point and the reset point Accurate measurements are possible only if the hysteresis band is narrow Triggering The set trigger level and trigger slope define the start and stop triggering If Auto is on the counter sets the trigger level to 50 of the signal amplitude which is ideal for most time measurements m Summary of Conditions for Reliable Time Measurements Auto Once that is freezing the levels de termined by Auto Trig is norma
112. s but is still within the display area Values that fall outside the dis play area are represented by a at the left edge or a gt at the right edge The location of the bars is fixed so the in side range takes up the mid third of the dis play area This means that the resolution and the scale length are set by the limits that have been entered by the operator Limits and Graphics Limits can also be applied to the two dimen sional graphics the trend plot and the histo gram By introducing limits you can inhibit the auto scaling and indirectly set the scale state length and the resolution Frequency f TZ MEAS Frequency A um noro 10 000 044 MHz 100 49 999 999 62 wiz 9 49 900 000 000MHz 50 100 000 000MHz Umax 1 490 U Umin 2 529U Up p 4 019 U Fig 6 3 The analog limit monitor Fig 6 4 Limits in a trend plot If Range is selected and the presentation mode is VALUES a one dimensional graphic representation of the current measurement Pree is x xs vase value in relation to the limits can be seen at the same time as the numerical value The upper limit UL and the lower limit LL are vertical bars below the main numerical display and their numerical values are dis played in small digits adjacent to the bars See Fig 6 3 500 mHz div 10 000 042 0 MHz 100 Fig 6 5 Limits in a histogram Limits and Graphics 6 7 Process This page is inte
113. se of the time between one trigger point and the next pa t FREQ A B 4 3 Measuring Functions RATIO A B B A C A C B To find the ratio between two input frequen cies the counter counts the cycles on two channels simultaneously and divides the result on the primary channel by the result on the secondary channel Ratio can be measured between Input A and Input B where either channnel can be the pri mary or the secondary channel Ratio can also be measured between Input C and Input A or between Input C and Input B Here Input C is the primary channel Note that the resolution calcula tions are very different as com pared to frequency measure ments See page 8 10 for details BURST A B C A burst signal as in Fig 4 2 has a carrier wave CW frequency and a modulation frequency also called the pulse repetition frequency PRF that switches the CW signal on and off Both the CW frequency the PRF and the number of cycles in a burst are measured without external arming signals and with or without selectable start arming delay See Chapter 5 Measurement Control for a fun damental discussion of arming and arming de lay The general frequency limitations for the re spective measuring channel also apply to burst measurements The minimum number of cy cles in a burst on Input A or Input B is 3 be low 160 MHz and 6 between 160 MHz and 300 MHz Burst measurements on Input C in volve prescaling so the min
114. set time The Hold Off pe 5 12 Arming Examples riod starts synchronously with the start trigger event The Hold Off time should be set to ex pire somewhere between pulse number 3 and 4 see Fig 5 14 Start Arm Trigger Hold Off Input A i y Fig 5 14 If Hold Off expires between pulses three and four the cor rect time interval is measured Use the same test setup as in the preceding examples Then proceed as follows Use the MEAS FUNC key to select Time Interval A to A Press INPUT B and choose positive slope and a suitable trigger level Press SETTINGS Trigger Hold Off On and enter a suitable Hold Off time Make sure the start arming conditions from example 1 are maintained i e no arming delay Measure m B Using Stop Arming i e External Hold Off to Delay the Stop So far in our examples the sync signal has been used exclusively as a start arming signal i e we have been concerned only about the leading edge of the sync signal and not its du ration However the sync signal can also be used as an External Trigger Hold Off when you select stop arming on the trailing edge of the sync signal If the duration of the sync pulses can be externally varied we can select a duration that expires in the gap between pulse 3 and 4 Sync E Start Arming Stop Arming Input A i F9 1 Fig 5 15 Using both start and stop arm ing t
115. sin gle shot phenomena which are either trig gered manually or occur at long intervals An other reason for using this manual arming could simply be to allow sufficient time to write down individual results m When Do I Use Start Arming Sync PE MENU EON Pulse Signal WWW WWW Fig 5 1 A synchronization signal starts the measurement when start arming is used Start arming is useful for measurements of fre quency in signals such as the following Single shot events or non cyclic signals Pulse signals where pulse width or pulse positions can vary Signals with frequency variations versus time profiling 5 6 The Measurement Process A selected part of a complex waveform signal Signal sources that generate complex wave forms like pulsed RF pulse bursts TV line signals or sweep signals usually also produce a sync signal that coincides with the start of a sweep length of an RF burst or the start of a TV line These sync signals can be used to arm the counter See Fig 5 1 m When Dol Use Stop Arming You normally use stop arming together with start arming That means that the external gating signal controls both the start and the stop of the measurement Such a gating signal can be used to force the counter to measure the frequency of a pulsed RF signal Here the position of the external gate must be inside a burst See Fig 5 2 Start Arm Stop Arm Ext Ga
116. sing OK A F LLIKES PM6690 FREQUENCY coun ER TIMER ANALYZER 100ps 300M gt IH MEAS AUTO FUNC SET EXIT bius CANCEL GATE TRIG O 300MHz B C 93 8GHz A Q 50N MAX 3 dBm 7 TRIGGER IN GATE INDI DICATORS CATOR Blinking LED in Pending mea dicates correct Surg p triggering vp es LED to light up NUMERIC INPUT KEYS Sometimes you may want to enter numeric values like the constants and limits asked for when you are utilizing the postprocessing features in MATH LIMIT mode These twelve keys are to be used for this purpose 2 4 Secondary Controls RF INPUT Optional Input C A number of RF prescalers are available covering different frequency ranges These units are fully automatic and no controls af fect the perfor mance The Type N connector is fit ted only if a prescaler is installed MAIN INPUTS The two identical DC coupled channels A amp B are used for all types of measure ments either one at a time or both together Using the Controls Rear Panel Type Plate Protective Ground Indicates instrument Terminal type and serial This is where the pro number tective ground wire is connected inside the in strument Never tamper Optional Main Input Fan with this screw Connectors A temp sensor controls the The front panel inputs can
117. speed of the fan Normal be moved to the rear panel bench top use means low Line Power Inlet by means of an optional ca speed whereas rack mount AC 90 265 VRMS ble kit Note that the input ing and or options may result 45 440 Hz no range capacitance will be higher in higher speed Switching needed O INPUT A INPUTB INPUT C A Reference Output External Arming Input USB Connector 10 MHz derived from the See page 5 7 Universal Serial Bus internal or if present the USB for data commu external reference nication with PC External Reference GPIB Connector Input Address set via User Op Can be automatically se tions Menu lected if a signal is pres ent and approved as timebase source see Chapter 9 Secondary Controls 2 5 Using the Controls Description of Keys Power The ON OFF key is a toggling secondary power switch Part of the instrument is always ON as long as power is applied and this standby condition is indicated by a red LED above the key This indicator is consequently not lit while the instrument is in operation Select Function This hard key is marked MEAS FUNC When you depress it the menu below will open Frequency fi RAE 4 253 774 43 mz Measure function Period Pulse Duty Time Phase Volt Fig 2 1 Select measurement function
118. still 2e tg See Table 4 1 to find the prescaling factors used in different operating modes m LF Signals Signals below 100 Hz should be measured with manual triggering unless the default set ting 100 Hz is changed See page 2 11 The low limit can be set to 1 Hz but the measure ment process will be slowed down consider ably if auto triggering is used in conjunction with very low frequencies Table 4 1 Prescaling factors When measuring pulses with a low repetition rate for example a 0 1 Hz pulse with a non prescaled function like PERIOD SGL the measurement will require at least the duration of one cycle that is 10 seconds and at worst nearly 20 seconds The worst case is when a trigger event took place just before the begin ning of a measurement time Fig 4 12 Mea suring the frequency of the same signal will take twice as long since this function involves prescaling by a factor two Possible trigger events v i v i 1 Pet measuring i time Gate time zl Time for one measurement L Fig 4 12 Measurement Time Even if you have chosen a short measurement time this measurement will require between 20 and 40 seconds for this example Theory of Measurement 4 11 Measuring Functions m RF Signals As mentioned before a prescaler in the C in put divides the input frequency before it is counted by the normal digital counting logic The division
119. sures frequency between 0 Hz and 300 MHz on Input A and Input B Frequencies above 100 Hz are best measured using the Default Setup See page 2 13 Then Freq A will be selected automatically Other important automatic settings are AC Cou pling Auto Trig and Meas Time 200 ms See below for an explanation You are now ready to start using the most common function with a fair chance to get a result without fur ther adjustments m Summary of Settings for Good Frequency Measurements AC Coupling because possible DC offset is normally undesirable Auto Trig means Auto Hysteresis in this case comparable to AGC because super imposed noise exceeding the normal nar row hysteresis window will be suppressed Meas Time 200 ms to get a reasonable tradeoff between measurement speed and resolution Some of the settings made above by recalling the Default Setup can also be made by activat ing the AUTOSET key Pressing it once means Auto Trig Note that this setting will be made once only if Man Trig has been se lected earlier Pressing AUTOSET twice within two sec onds also adds the following setting Meas Time 200 ms FREQ C With an optional prescaler the counter can measure up to 3 GHz or 8 GHz on Input C These RF inputs are fully automatic and no setup is required Trigger level offset ruv Trigger points t 4 Reset points Fig 4 1 Frequency is measured as the inver
120. t can process the measurement results on your benchtop with out the need for a controller Math functions include inversion scaling and offset Statistics functions include Max Min and Mean as well as Standard and Allan Deviation on sample sizes up to 2 10 No Mistakes You will soon find that your instrument is more or less self explanatory with an intuitive user interface A menu tree with few levels makes the timer counter easy to operate The large backlit graphic LCD is the center of in formation and can show you several signal pa rameters at the same time as well as setting status and operator messages Statistics based on measurement samples can easily be presented as histograms or trend plots in addition to standard numerical mea surement results like max min mean and standard deviation The AUTO function triggers automatically on any input waveform A bus learn mode sim plifies GPIB programming With bus learn mode manual counter settings can be trans ferred to the controller for later reprogram ming There is no need to learn code and syn tax for each individual counter setting if you are an occasional bus user Preparation for Use Design Innovations State of the Art Technology Gives Durable Use These counters are designed for quality and durability The design is highly integrated The digital counting circuitry consists of just one custom developed FPGA and a 32 bit microcontroller The high int
121. t is visibly damaged One such symbol is printed on the instrument below the A and B inputs It points out that the damage level for the input voltage decreases from 350 Vp to 12Vims when you switch the input impedance from 1 MQ to 50 Q If in Doubt about Safety Whenever you suspect that it is unsafe to use the instrument you must make it inoperative by doing the following Disconnect the line cord Clearly mark the instrument to prevent its further operation 1 6 Safety Preparation for Use Unpacking Check that the shipment is complete and that no damage has occurred during transportation If the contents are incomplete or damaged file a claim with the carrier immediately Also no tify your local Fluke sales or service organiza tion in case repair or replacement may be re quired Check List The shipment should contain the following Counter Timer Analyzer Model 90 Line cord N to BNC Adapter only if one of the prescaler options has been ordered Printed version of the Getting Started Manual Brochure with Important Information Certificate of Calibration Options you ordered should be installed See Identification below CD including the following documentation in PDF Getting Started Manual Operators Manual Programming Manual Identification The type plate on the rear panel shows type number and serial number See illustration on page 2 5 In the menu
122. te Burs Si ig WHI Ill e HW Fig 5 2 Start and stop arming together is used for burst signal gating Note that burst measurements with access to an external sync signal are performed in the normal Frequency mode whereas burst measurements without an external sync signal are performed in the self synchronizing Fre quency Burst mode In time interval measurements you can use the stop arming signal as a sort of external trigger Hold Off signal Here you block stop triggering during the external period See Fig 5 3 Stop Arm Start Arm Fig 5 3 Using arming as an external Hold Off m The Arming Input Input E is the normal arming input It is suitable for arming sync signals that have TTL levels The trigger level is fixed at 1 4V and cannot be changed The trig ger slope can be set to positive or nega tive The Input E connector can be found on the rear panel of the instrument Input A or Input B can also be used as arming input for all single channel mea surements and dual channel measurements where the arming signal is one of the mea suring signals This input is more suitable if your arming signal does not have TTL levels All input controls such as AC DC Trigger Level 50 Q 1 MQ etc can be used to condition the arming signal Using the measuring signal as arming signal When performing time or frequency measure ments on comple
123. tect setup setup labels ON Fig 2 23 The memory management menu Twenty complete front panel setups can be stored in non volatile memory Access to the first ten memory positions is prohibited when Setup Protect is ON Switching OFF Setup Protect releases all ten memory positions si multaneously The different setups can be in dividually labeled to make it easier for the op erator to remember the application The following can be done Save current setup Frequency A Meas 90 000 001 77 mz User options Save Recall Save current setup A 2 3 4 5 l Next Fig 2 24 Selecting memory position for saving a measurement setup Browse through the available memory positions by using the RIGHT LEFT arrow keys For faster browsing press the key Next to skip to the next memory bank Press the softkey below the num ber 1 20 where you want to save the setting Recall setup Frequency A Meas 00 000 001 76 mz User options Save Recall Recall setup 1 4 5 L l Next Fig 2 25 Selecting memory position for recalling a measurement setup Select the memory position from which you want to retrieve the contents in the same way as under Save current setup above You can also choose Default to restore the preprogrammed factory set tings See the table on page 2 15 for a complete list of these settings Modify labels Select a memory position to
124. ted as 360 x Time Interval A B Period or in other words Phase A B 2 360 x Time Delay x FREQ A somewhat more elaborate method is used in these counters It allows the necessary mea surements to be performed in one pass by us ing time stamping Two consecutive time stamps from trigger events on channel A and two corresponding time stamps from channel B are enough to calculate the result including sign Resolution Period T B Time delay At e i4 At 3609 T Fig 4 19 Traditional phase definition The frequency range for phase is up to 160 MHz and the resolution depends on the frequency For frequencies below 100 kHz the resolution is 0 001 and for frequencies above 10 MHz it is 1 It can be further improved by averaging through the built in statistics func tions What is Phase 4 17 Measuring Functions Possible Errors Phase can be measured on input signal fre quencies up to 160 MHz However at these very high frequencies the phase resolution is reduced to 100ps x 360 x FREQ Inaccuracies The inaccuracy of Phase A B measurements depends on several external parameters Input signal frequency Peak amplitude and slew rate for input sig nals A and B Input signal S N ratio Some internal parameters are also important Internal time delay between channel A and B signal paths Variations in the hysteresis window be tween chan
125. the ac tual oscillator used See Timebase Options on page 8 14 Total Uncertainty 20 The general formula for all measurement functions is Ur 2 J rand uncert syst uncert y Time Interval Pulse Width Rise Fall Time m Random Uncertainty rms U ud Jd Error StopTrig Error s m Systematic Uncertainty Uss A 4 Ev 500 psy TBE TIME where Eq trigger level timing error 500 ps maximum channel difference TBE timebase error TIME measurement result Frequency amp Period m Random Uncertainty rms For measuring times lt 200 ms and if Smart Freq AUTO or OFF fe 2 Start Trigger Error x U rnd Measuring Time x Measurement Result Hz or s For measuring times gt 200 ms and if Smart Freq AUTO or ON 2s qe t 2 Start Trigger Error U x rnd Measuring Time 4 N x Measurement Result Hz or s N 800 Measuring Time however 6 lt N lt 1000 and N lt Freq 2 Measuring Time 2 m Systematic Uncertainty Us Ke TBE MR 200 ps MT MR Hz or s where MR Meas Result Freq or Per MT Meas Time Frequency Ratio f f m Typical Random Uncertainty rms NOTE Frequency Ratio is an auxiliary mea surement function intended to give an indica tion with no guaranteed specification Uma 2 x presc fact x fi x Ez Esm ES dimensionless e g ppm
126. toff frequency that is too high gt 2 times the input frequency also leads to a stable reading Here one noise pulse is counted for each half cycle Use an oscilloscope for verification if you are in doubt about the frequency and waveform of your input signal The cutoff frequency setting range is very wide 1 Hz 50 MHz i Hold off time Correct measurement Fig 3 8 Digital LP filter operates in the measuring logic not in the input amplifier Man Auto Toggle between manual and automatic trigger ing with this softkey When Auto is active the counter automatically measures the peak to peak levels of the input signal and sets the trigger level to 50 of that value The attenuation is also set automatically At rise fall time measurements the trigger lev els are automatically set to 10 and 90 of the peak values When Manual is active the trigger level is set in the value input menu designated Trig See below The current value can be read on the display before entering the menu m Speed The Auto function measures amplitude and calculates trigger level rapidly but if you aim at higher measurement speed without having to sacrifice the benefits of automatic trigger ing then use the Auto Trig Low Freq func tion to set the lower frequency limit for volt age measurement If you know that the signal you are interested in always has a frequency higher than a cer
127. uency FM Channel See Input Confidence Limits Count error 1 cycle Counting reciprocal CW DGC coupling 2 mn es Delay arming Sync Delayed timebase Display Contrast adjusting Distortion See Also Long time instability Drift measurements 5 13 Duty cycle See Duty factor E End ofameasurement 5 4 Erroneous countS 3 7 Error NO TRIG 4 10 Examples arming s eie tated ke dos 5 9 Ext Arm Input Checking 7 9 External gate 5 6 F Filter analog eor RR 3 3 Fixed timeout 1 csse cx RES 4 10 Fixed triggerlevels 3 5 FMisighals c gegen 4 6 Free running measurements 5 4 5 13 Freezing the display See hold run Frequency cese eR ei eds 4 3 Range test 7 5 zuo 4 4 Frequency versus time See Profiling Function period rw e 4 12 MAUS IER TEE 4 4 Gate indicator lille 5 2 Index H Harmonic distortion 3 8 Hold or ctor rete pns 5 6 Hold Off checking 7 10 used as filter 3 4 Hysteresis 3 6 4 15 Input Controls Checking mn 7 8 Instability 2 05 6 4 Internal Reference output Checking 7 9 J SII IM T T DEEEETER RERO 6 4 L LCD Contrast
128. uency resolution per sec ond and 100 ps resolution as a result of high resolution interpolating reciprocal counting RF prescaler options with upper frequency limit of 3 GHz or 8 GHz Integrated high performance GPIB inter face using SCPI commands A fast USB interface that replaces the tra ditional but slower RS 232 serial interface Timestamping the counter records exactly when a measurement is made A high measurement rate of up to 250 k readings s to internal memory Optional oven controlled timebase oscillators 1 2 Preface Powerful and Versatile Functions A unique performance feature in your new in strument is the comprehensive arming possi bilities which allow you to characterize virtu ally any type of complex signal concerning frequency and time For instance you can insert a delay between the external arming condition and the actual arming of the counter Read more about Arm ing in Chapter 5 Measurement Control In addition to the traditional measurement functions of a timer counter these instruments have a multitude of other functions such as phase duty factor rise fall time and peak voltage The counter can perform all measurement functions on both main inputs A amp B Most measurement functions can be armed either via one of the main inputs or via a separate arming channel E By using the built in mathematics and statis tics functions the instrumen
129. uently faster measurements Timeout From this submenu you can activate de activate the timeout function and set the maximum time the instrument will wait for a pending measurement to finish be fore outputting a zero result The range is 10 ms to 1000 s m Math Limit Frequencu fi Meas 90 000 001 77 mz Math Limit zi Limits Fig 2 17 Selecting Math or Limits pa rameters You enter a menu where you can choose be tween inputting data for the Mathematics or the Limits postprocessing unit Frequency fi mar 4 194 673 693 mz Math Limit Math Math K L n Off 1E0 0 EO 1E0 Fig 2 18 The Math submenu The Math branch is used for modifying the measurement result mathematically before presentation on the display Thus you can Description of Keys 2 11 Using the Controls make the counter show directly what you want without tedious recalculations e g revo lutions min instead of Hz The Limits branch is used for setting numeri cal limits and selecting the way the instrument will report the measurement results in relation to them Let us explore the Math submenu by pressing the corresponding softkey below the display The display tells you that the Math function is not active so press the Math Off key once to open the formula selection menu Frequency A MEAS 4 222 931 86 mz Math Limit Math Math K K L K X L K X L KL OM Mo OXM 1 Fig 2
130. usually measure both the car rier wave frequency and modulation fre quency of AM signals These measurements 4 8 AM Signals are much like the burst measurements de scribed earlier in this manual Carrier Wave Frequency The carrier wave CW is only continuously present in a narrow amplitude band in the middle of the signal if the modulation depth is high If the sensitivity of the counter is too low cycles will be lost and the measurement ruined t i Fig 4 8 Effects of different sensitivity when measuring the CW Fre quency of an AM signal To measure the CW frequency Enter the INPUT A menu Select a measurement time that gives you the resolution you want Turn on Manual trigger Press Trig level and enter 0 V trigger level press the numeric key 0 and EXIT OK Select AC coupling Select 1x attenuation to get a narrow hys teresis band f the counter triggers on noise widen the hysteresis band with the variable hyster esis function i e enter a trigger level 70 V but lt Vp pmin See Fig 4 8 Modu
131. ut signal as suming that Vpp is the main parameter 1 Vins T 2 pp CF EXAMPLE A sine wave has a crest factor of 1 414 4 2 so the constant in the for mula above will be 0 354 Press MATH LIM and after that Math Math Off K X L Press K and enter 0 354 via the NUMERIC ENTRY keys Check that the L con stant is set to its default setting 0 Con firm your choices with the softkeys be low the display If the input is AC cou pled and Vpp selected the display will now show the RMS value of any sine wave input Ifthe sine wave is superimposed on a DC voltage the RMS value is found as 0 354 Vpp Voc If Vpc is not known it can be found as To display the rms value of a sine wave super imposed on a DC voltage follow the example above but set L Vpc Measuring Functions VRMS 4 23 Measuring Functions This page is intentionally left blank 4 24 VRMS Chapter 5 Measurement Control Measurement Control About This Chapter This chapter explains how you can control the start and stop of measurements and what you can obtain by doing so The chapter starts by explaining the keys and the functions behind them then gives some theory and ends with actual measurement examples Measurement Time This parameter is only applicable to the func tions Frequency and Period Average In creasing the measurement time gives more digits i e higher resolution but fewer mea surements per second
132. ver from AUTO to MAN Trig ger Level is automatic if you enter a trigger level manually m Auto Once Converting Auto to Fixed The trigger levels used by the auto trigger can be frozen and turned into fixed trigger levels simply by toggling the MAN AUTO key The current calculated trigger level that is visible on the display under Trig will be the new fixed manual level Subsequent measurements will be considerably faster since the signal levels are no longer monitored by the instru ment You should not use this method if the signal levels are unstable NOTE You can use auto trigger on one input and fixed trigger levels on the other Input Amplifier 3 5 Input Signal Conditioning How to Reduce or Ignore Noise and Interference Sensitive counter input circuits are of course also sensitive to noise By matching the signal amplitude to the counter s input sensitivity you reduce the risk of erroneous counts from noise and interference These could otherwise ruin a measurement a Fig 3 10 Narrow hysteresis gives errone ous triggering on noisy signals Fig 3 11 Wide trigger hysteresis gives correct triggering To ensure reliable measuring results the coun ter has the following functions to reduce or eliminate the effect of noise 10x input attenuator Continuously variable trigger level Continuously variable hysteresis for some functions Analog l
133. voltage ref erence alternatively corresponding DC power supply DVM with uncertainty 0 1 LF Synthesizer Square Sine up to 10 MHz 10 Vams Pulse Generator 2 ns rise time 5 V peak gt 10 MHz continuous amp one shot trigger Oscilloscope 350 MHz 396 voltage uncertainty RF Signal Generator 100 MHz to 3 or 8 GHz dep on prescaler option 10 MHz ext ref Power Splitter 50 Q 6 dB BNC T piece BNC Termination 50 Q feedthrough BNC Lowpass Filter 50 kHz for 4 MQ BNC Cables 5 to 7 pcs of suitable lengths Table 7 1 Recommended equipment for calibration and performance check 7 2 General Information Front Panel Controls Internal Self Tests The test programs forming the self diagnosis can be activated from the front panel as fol lows Press USER OPT Press Test Press Test Mode Select one of the six tests available by pressing the softkey below the label with the name of the test function Five of the tests RAM ROM Logic Display and In terface are individual They are briefly described below The sixth named All performs all five individual tests in se quence e All all tests performed in sequence e RAM test of RAM memory ROM test of ROM memory Logic test of counter ASIC and other logic circuits Display test of graphic display module Interface test of GPIB and USB Press Start
134. wer is a potential danger to life Handling restrictions imposed on such equipment should be observed To ensure the correct and safe operation of the instrument it is essential that you follow gen erally accepted safety procedures in addition to the safety precautions specified in this man ual The instrument is designed to be used by trained personnel only Removing the cover for repair maintenance and adjustment of the instrument must be done by qualified person nel who are aware of the hazards involved The warranty commitments are rendered void if unauthorized access to the interior of the instrument has taken place during the given warranty period Safety 1 5 Preparation for Use Caution and Warning Statements 122 CAUTION Shows where incorrect procedures can cause damage to or destruction of equipment or other property WARNING Shows a potential danger that requires correct procedures or practices to prevent personal in jury Symbols Fig 1 1 Do not overlook the safety in D structions Shows where the protective ground S KE nform your Fluke representative terminal is connected inside the instrument Never remove or loosen this screw a This symbol is used for identifying the functional ground of an I O signal It is always connected to the instrument chassis N Indicates that the operator should consult the manual For example the instrument is likely to be un safe if i
135. wer than fp The statisti cally averaged value of the frequency fmean approaches f when the number of averaged samples is sufficiently large When the counter measures instantaneous fre quency values when you select a very short measurement time the RMS measurement uncertainty of the measured value of fo is 1 fmean where n is the number of averaged samples of f xA fmax fmax Press SETTINGS STAT and set No of samples to 1000 or more Press Meas Time and select a low value Press STAT PLOT and watch fmax fmin Press SETTINGS STAT and set No of samples to 1000 or more Press Meas Time and select a low value Press STAT PLOT and watch fmin Frequency Modulated Signals 4 7 Measuring Functions Afp p Press SETTINGS STAT and set No of samples to 1000 or more Press Meas Time and select a low value Press STAT PLOT and watch Afy p Mfp p fmx fun 2 x Af Errors in fmax fui and Afp p A measurement time corresponding to J cy cle or 36 of the modulation signal leads to an error of approx 1 5 Select the measurement time 1 t ELS 10 x Srnodutation measure gt Modulation f p signal Fig 4 7 Error when determining fmax To be confident that the captured maximal fre quency really is fmax you must select a suffi ciently large number of samples for instance n z 1000 AM Signals The counter can
136. which you want to assign a label See the descrip tions under Save Recall setup above Now you can enter alphanumeric char acters from the front panel See the fig ure below The seven softkeys below the display are used for entering letters and digits in Using the Controls the same way as you write SMS mes sages on a cell phone Setup protection Toggle the softkey to switch between the ON OFF modes When ON is ac tive the memory positions 1 10 are all protected against accidental overwriting User options Save Recall Modify Labels Setup 1 label labc 2def 3ghij 4klmn Sopar stuv wxuz t 2 3 a s E 674801 me 6 Li 7 s J Fig 2 26 Entering alphanumeric charac ters Calibrate Menu This menu entry is accessible only for calibra tion purposes and is password protected Interface Menu Frequency A MEAS 4 194 BB 535 mz User options Interface GPIB GPIB Mode Address GPIB Native 10 Fig 2 27 Selecting active bus interface Bus Type Select the active bus interface The alterna tives are GPIB and USB If you select GPIB you are also supposed to select the GPIB Mode and the GPIB Address See the next two paragraphs Description of Keys 2 13 Using the Controls GPIB Mode There are two command systems to choose from Native The SCPI command set used in this mode fully exploits all the features of this instru ment series
137. x signals having a unique trigger point input B arming can be used to make the measuring signal itself auto arm the counter e g to measure the frequency of a signal after it has reached a specified voltage limit set trigger level see Fig 5 4 Connect the signal to input A Measurement Control Press INPUT A and adjust the settings to suit the interesting part of the signal Press INPUT B and adjust the settings so that the unique trigger point can be de tected Normally DC coupling and Manual trigger level should be preferred Activate start arming with or without de lay on input B via the SETTINGS menu The signal on input A will be internally con nected to input B so no external signal tap is necessary m When Do Use Arming With Delay You can delay the start arming point with re spect to the arming signal Use this function when the external arming signal does not co incide with the part of the signal that you are interested in The time delay range is 20 ns to 2 s with a set ting resolution of 10 ns Getting The Whole Picture The flowchart in Fig 5 5 illustrates how arm ing a trigger hold off enables precise control of the start and stop of the actual measurement when you operate the counter from the front panel If you control the counter via the GPIB or USB read more about bus arming and trig gering under the heading How to use the trig ger system in the Programming
138. y re duces the resolution Making burst frequency measurements on short bursts means using short measurement times giving a poorer res olution than normally achieved with the coun ter m How Does the Sync Delay Work The sync delay works as an internal start arm ing delay it prevents the start of a new mea surement until the set sync delay has expired See Fig 4 5 After the set measurement time has started the counter synchronizes the start of the mea surement with the second trigger event in the burst This means that the measurement does BURSTA B C 4 5 Measuring Functions not start erroneously during the Burst Off du ration or inside the burst Measure AN l TIR T pu UN mur Sync de Gate Time Fig 4 5 Measuring the frequency of the carrier wave signal in a burst m Possible Errors Before the measurement has been synchro nized with the burst signal the first measure ment s could start accidentally during the presence of a burst If this would happen and if the remaining burst duration is shorter than the set measurement time the readout of the first measurement will be wrong However after this first measurement a properly set start arming sync delay time will synchronize the next measurements In manually operated applications this is not a problem In automated test systems where the result of a single measurement sample must

Timer/Counter/ Analyzer

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