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CNT-90 Series User`s Manual

1. 8 14 Ordering Information 8 14 Timebase Options 8 15 Explanations 8 15 CNT 90XL oe ce Sree oria eraa 8 16 Introduction cemere 8 17 Measurement Functions 8 17 FrequencyA B C 8 17 Frequency Burst A B 8 17 Period A B C Average 8 18 Period A B Single 8 18 Ratio A B B A C A C B 8 18 Time Interval A to B B to A Ato A Bio Bia iesieen ev heuer ER S 8 18 Pulse WidthA B 8 18 Rise and Fall Time A B 8 18 Phase ARel B BRel A 8 19 Duty FactorA B 8 19 Vinac Vmins Veep Ai Be rese 8 19 POWER C sisse ch bined EE EORR te 8 19 Timestamping A B 8 20 Auto Set Manual Set 8 20 Input and Output Specifications 8 20 Inputs AandB 8 20 ojo qoe ME EA 8 21 Rear Panel Inputs amp Outputs 8 21 Auxiliary Functions 8 22 Trigger Hold Off 8 22 External Start Stop Arming 8 22 StatistiCS ed reo oec toe rd 8 22 Mathematics esee 8 22 Other Functions 8 22 Display i5 mede ts 8 23 GPIB Interface sce e 8 23 USB Interface lusus 8 23 TimeView 2 0 eee ee eee 8 23 Battery Unit 8 24 Option 23 90 oo oc seems 8 24 Measurement Uncertainties 8 24 Random Uncertainties
2. 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 Dol 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 Programmer s Handbook FREQA A B Set Measuring Time Trigger Level AAA B n NS Unique Input Trigger signal Point B Fig 5 4 Auto arming using the trigger level on B as qualifier The Measu
3. 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 Performance Check Increase the Trigger Hold Off time in steps by means of the UP cursor key and note the results If Trigger Hold Off time lt 100 ns the result is about 100 ns i e the same value as without Hold Off Selected Function Action Display P F FREQA 10 MHz FREQ B 10 MHz FREQ C CNT 90 500 MHz 15 dBm 500 MHz CNT 90XL 5 GHz 15 dBm 5 GHz FREQ RATIO A B 12 FREQ RATIO C B 502 9 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 POS A 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 Value depends on the symmetry of the signal 2 Exact value depends on input signal 3 If an RF option is installed Check of HOLD OFF Function 7 11 Performance Check If Trigger Hold Off time gt 100 ns
4. 500ps x Freq x 360 7 6 26 CNT 90XL Measurement Uncertainties Duty Factor m Random Uncertainty rms Uma Ee Strt Trg Err Stop Trg Err x Freq or minimum 1 ppm m Systematic Uncertainty U ss Jx Ev 200 psy x Freq dimensionless e g ppm 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 Specifications 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 specification See also timebase specifications on page 8 30 CNT 90XL Calibration 8 27 Specifications 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
5. 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 measures 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 500 s The pac ing parameter sets the sampling interval Activate the set pacing time by pressing Pacing Off The status is changed to Pacing On Status Pacing Off means 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 displa
6. 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 gt 2 s are software controlled w reduced res olution and accuracy Internal external or auto matic 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 Limit Alarm Limit Values Settings On Alarm Display Numeric Graphic Stored Instrument Setups Display Type amp Use Resolution Technology Specifications Annunciator on display and or SRQ via GPIB Lower limit limit 1 Upper limit limit 2 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 limit 1 Stop or Continue Numeric graphic Current measurement value annunciator for limit alarm Horizontal line w up per lower limit markers current value marker 20 complete setups can be saved and recalled from internal non volatile memory 10 can be user protected Graphics screen for menu control numerical readout 14 digits and status info 320 x 97 pixels Monochrome LCD with white LED backlight GPIB Interface Programmable Functions Compatibility Modes All front panel accessible functions IEEE 488 2 1987 SCPI 1999 Native mode Agilent compatible mode CNT 90 Auxiliary Function
7. Connector Type N female Input C Option 13 300 MHz 8 GHz Prescaler Factor 256 Freq Range Operating input voltage range 0 3 0 5 GHz 20 mVrms 7 Vrms 0 5 3 0 GHz 10 mVrms 7 Vrms 3 0 4 5 GHz 20 mVrms 7 Vrms 4 5 6 0 GHz 40 mVrms 7 Vrms 6 0 8 0 GHz 80 mVrms 7 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 Max Voltage w o Damage 7 Vrms PIN diode protected Connector Type N female Input and Output Specifications 8 7 Specifications Input C Options 14 amp 14B Freq Range 250 MHz 15 GHz 14 250 MHz 20 GHz 14B Prescaler Factor 128 Operating input voltage range 0 25 0 5 GHz 21 to 27 dBm 0 5 15 GHz 27 to 27 dBm 14 18 GHz 27 to 27 dBm 14B 18 20 GHz 21 to 27 dBm 14B AM tolerance Up to 90 depth Burst Minimum Burst Length Period x 257 Minimum Interval Between Bursts 10 us Impedance 50 Q nom AC coupled VSWR lt 2 1 Max Voltage w o Damage Connector Type N female Rear Panel Inputs amp Outputs Ref Input 1 5 or 10 MHz 0 1 5 Vrms sinewave impedance gt 1 kQ Ref Output 1x10 MHz gt 1 Vrms into 50 Q load Arming Input E Arming of all meas func Freq Range DC 80 MHz Trigger Level TTL 1 4 V nom Trigger Slope Positive or ne
8. 16 8 24 Systematic Uncertainties 8 24 Total Uncertainty 26 8 25 Time Interval Pulse Width Rise Fall DI ST D D 8 25 Frequency amp Period A B 8 25 Frequency amp PeriodC 8 25 Frequency Ratio fa fs or fg f 8 26 Frequency Ratio fc f4 or fc fs 8 26 PHASE rese EREEH RO ED uar 8 26 Duty AE ACIOE cire et ene pies 8 26 Calibration rnm 8 26 Definition of Terms 8 26 General Specifications 8 27 Environmental Data 8 27 Power Requirements 8 27 Dimensions amp Weight 8 28 Ordering Information 8 28 Timebase Options 8 29 Explanations 8 29 CGNT 0dM R cor 8 30 Introduction 2 005 8 31 Measurement Functions 8 31 Frequency A B C 8 31 Frequency Burst A B C 8 31 Period A B C Average 8 31 Period A B Single 8 32 Period A B Back to Back 8 32 Ratio A B B A C A C B 8 32 Time Interval A to B B to A Ato A B lo B sese ceri endet Turm 8 32 Pulse WidthA B 8 32 Rise and Fall Time A B 8 32 Time Interval Error TIE A B 8 33 Phase A Rel B BRel A 8 33 Duty Factor A B 8 33 Vrngo Vmin Vp AG B cete 8 33 Totalize A B A B A B A B 8 34 Timestamping A B 8 34
9. Auto Set Manual Set 8 34 Input and Output Specifications 8 35 Inputs AandB 8 35 Input C Option 10 8 35 Input C Option 13 8 36 Input C Options 14 amp 14B 8 36 Rear Panel Inputs amp Outputs 8 36 Auxiliary Functions 8 37 Trigger Hold Off 8 37 External Start Stop Arming 8 37 Statistics ox era dent 8 37 Mathematics 8 37 Other Functions 8 37 Display eR RR ERREUR 8 38 GPIB Interface 8 38 USB Interface 8 38 TIMOVIEW Mic cae setae eee ae 8 39 Measurement Uncertainties 8 39 Random Uncertainties 10 8 39 Systematic Uncertainties 8 39 Total Uncertainty 20 8 40 Time Interval Pulse Width Rise Fall TIME 5 s eea inaa n a riter ors 8 40 Frequency amp Period 8 40 Frequency Ratio fi fo 8 41 PASC eon bed 8 41 Duty Factor sic 2 verme Dd 8 41 Calibration rep 8 41 Definition of Terms 8 41 General Specifications 8 42 Environmental Data 8 42 Power Requirements 8 42 Dimensions amp Weight 8 42 Ordering Information 8 43 Timebase Options CNT 91 8 44 Explanations 8 44 Timebase Specifications CNT 91R 8 45 Explanations esk 8 45 9 Index 10 Ser
10. 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 Max Frequency to catch each edge 70 ps rms 250 kHz Auto Set Manual Set All measuring functions can be auto set using best 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 400 MHz AC coupled 10 Hz 400 MHz Coupling AC or DC Rise Time Approx 700 ps Impedance 1 MO 25 pF or 50 Q VSWR 2 Trigger Slope Positive or negative Channels Separate A amp 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 300 400 MHz 35 mVrms Auto Trig 35 mVrms Attenuation x1 x10 Dynami
11. Option 30 90 Option 40 90 Timebase Type UCXO OCXO OCXO OCXO Uncertainty due to Calibration adjustment tolerance 6 8 8 9 23 C 3 C lt 1x10 lt 5x10 lt 1x10 3x10 Aging per 24 h 1 2 lt 5x10 P lt 5x1010 2 344970 per month 5x107 6x10 1x10 3x10 per year lt 5x10 lt 2x10 5x109 15x10 Temperature variation 0 C 50 C 1x10 5x10 5x10 2 5x10 20 C 26 C typ values lt 3x10 lt 2x108 1x10 x10 Power voltage variation 10 1x10 5x10 5x10 10 5x10 1 Short term stability Root Allan Variance EN 10 11 12 t 1 s not specified 1x10 1x10 5x10 Typical values t 10 s 1x10 1 txtio 5x10 Power on stability 1 a P 3 Deviation versus final value after 24 h 1x10 1x10 5x10 on time after a warm up time of 30 min 30 min 10 min 10 min Total uncertainty for operating temperature 0 C to 50 C 2c 95 confidence interval 1 year after calibration 12x10 2 4x107 6x109 1 8x10 2 years after calibration 1 5x107 46x107 12x107 3 6x10 Typical total uncertainty for op erating temperature 20 C to 26 C 2c 95 confidence interval 6 7 8 8 1 year after calibration lt 7x1 ue lt 2 4x1 03 lt 6x1 03 lt 1 7x1 0 a 2 years after calibration lt 1 2x10 lt 4 6x10 lt 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 oper
12. Parameter A B Vmax Vmin Vp p Period A B Single Range A B 3 3 ns 1000 s Resolution 50 ps rms typical m Display Main Parameter Period Aux Parameters Vmax Vmin Vp p Period A B Back to Back Range A B 4ns 500s Resolution 50 ps rms typical m Display Main Parameter Period Aux Parameters Vmax Vmin Vp p Ratio A B B A C A C B Range 10 to 10 one pass measurem values 1 with reduced resolution Freq Range A B 100 Hz to 400 MHz Freq Range C Full input C range m Display Main Parameter Ratio Aux Parameters Freq 1 Freq 2 Time Interval A to B B to A AtoA BtoB Range normal calculation 0 ns to 4108 S Range smart A calculation 10 to 10 s Resolution Single Shot 50 ps rms typical Specifications 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 m Display Main Parameter Time interval Aux Parameters None Pulse Width A B Range 2 5 ns 108 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 Trigger Levels Default 10 and 90 Manually adjustable Min Pulse Width 1 6 ns Modes Rise or f
13. Resolution 12 digits s m Display Main Parameter Period Aux Parameter A B Vmax Vmin Vp p CNT 90 Introduction 8 3 Specifications Period A B Single m Display Range A B 3 3 ns 1000 s Main Parameter Time interval Resolution 100 ps Aux Parameters None m Display Pulse Width A B 6 Main Parameter Period Range 2 5 ns 10 s Aux Parameters Vmax Vmin Vp p Input Frequency Up to 200 MHz Modes Pos pulse width or Ratio A B B A C A C B neg pulse width Range 10 to 1011 one pass m Display measurem values 1 with reduced resolution Main Parameter Pulse width Freq Range A B 100 Hz to 400 MHz Aux Parameters Vmax Vmin Vp p Freq Range C Full input C range Rise and Fall Time A B m Display Range 1 5 ns 1000 s Main Parameter Ratio Input Frequency Up to 160 MHz square Aux Parameters Freq 1 Freq 2 wave Trigger Levels Default 1096 and 9096 Time Interval A to B B to A Manually adjustable A to A B to B Min Pulse Width 1 6 ns Modes Rise or fall time Range normal Min Amplitude 100 mVp p calculation Onsto 10 s isi doen 10 to 108 s M Display Resolution Main Parameter Rise or fall time Single Shot 100 ps Aux Parameters Slew rate Vmax Vmin 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 6 4 CNT 90 M
14. and select Freq A Check that the instrument is working and shows a value close to 10 MHz Disconnect the power cord and check that the instrument goes on working Note The power plug symbol disappears leav ing the battery symbol alone Check that the instrument operates gt 4 5 h without connection to the mains Power down the instrument by pressing the green power switch key Check that the red standby LED lights up Power up the instrument again and check that it powers down automatically when the battery is almost empty Connect the power cord and power up the instrument Check that the standby LED goes out Check that the status indicator shows a charging battery symbol Let the battery charge to its full capacity Power down wait 10s and power up Press USER OPT Misc and select Use Battery in Standby No to make sure the instrument will not continue to operate in case line power fails Note The battery symbol disappears leaving the power plug symbol alone Disconnect the power cord and check that the instrument stops working The standby LED shall not light up 7 14 Battery Supply Chapter 8 Specifications Specifications CNT 90 8 2 CNT 90 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 41 f
15. 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 can perform jitter analysis on several tens of thou sands of pulse width measurements and cap ture them in a second An extensive Programmer s Handbook helps you understand SCPI and counter program ming 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
16. lt 6x10 2 lt 5x1 Qu 2 lt 3x1 07 per month 5x10 6x10 lt 1x10 lt 3x1 0s per year 5x10 2x10 5x10 1 5x10 Temperature variation 0 C 50 C lt 1x10 5x107 5x107 2 5x107 20 C 26 C typ values 3x10 2x10 1x10 4x10 Power voltage variation 10 1x10 5x10 5x10 10 5x10 19 Short term stability Root Allan Variance 10 11 12 t 1 s not specified 1x10 i 1x10 jd 5x10 ia Typical values t 10 s 1x10 1x10 5x10 Power on stability 7 B Deviation versus final value after 24 h 1x10 1x10 5x10 on time after a warm up time of 30 min 30 min 10 min 10 min Total uncertainty for operating temperature 0 C to 50 C 2c 95 confidence interval 5 7 8 8 1 year after calibration lt 1 2x10 24x10 6x10 1 8x1 M 2 years after calibration 1 5x10 4 6x10 1 2x10 3 6x10 Typical total uncertainty for op erating temperature 20 C to 26 C 2c 95 confidence interval 6 7 8 8 1 year after calibration lt 7x1 p lt 2 4x1 0 lt 6x1 o lt 1 7x1 M 2 years after calibration 1 2x10 4 6x10 lt 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 Uncompensa
17. 000 001 76 mz Settings MeasTime ms us s Submenu for entering measur ing time Fig 2 12 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 50 000 001 76 mz Settings Burst Frequency EXHIBET Start delay Meas time Limit 200 us 200 us 200 us 300 MHz Fig 2 13 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 fre quency the pulse repetition frequency PRF can be measured often without the support of an external arming signal Arm Frequency A Meas 50 000 001 76 mz vettings Arm Start Start Arm Stop Stop ME Slope delay Chan Slope Off d 200 us Off I Fig 2 14 CNT 90 amp CNT 90XL Setting arming conditions Frequencu fi MEAS 4 181 045 665 2 mz Settings Arm Guu Start Start Start Stop Stop Stop iim Chan Slope Delay Delay Chan Slope EEWO OFF I Os 0s OFF 1 Fig 2 15 CNT 91 R Setting arming con ditions 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 conditi
18. 13 Option 14 Option 14B Timebase Op tions Option 19 90 Option 30 90 Option 40 90 8 14 CNT 90 Ordering Information Timer Counter including standard timebase and GPIB interface 18 months product war ranty line cord brochure with important information getting started manual user s manual and pro grammer s handbook on CD Certificate of Calibra tion 3 0 GHz Input C 8 GHz Input C 15 GHz Input C 20 GHz Input C Medium stability OCXO Very high stability OCXO Ultrahigh stability OCXO Optional Accessories Option 11 90 Option 22 90 Option 23 90 Option 27 Option 27H Option 29 90 Option 90 01 Option 90 06 Option 90 00 Option 95 03 Option 95 05 Printed Manuals CNT 90 amp CNT 91 R amp CNT 90XL CNT 90 amp CNT 91 R amp CNT 90XL CNT 90 amp CNT 91 R amp CNT 90XL Rear panel inputs Rackmount kit Battery supply unit Carrying case Heavy duty hard transport case TimeView for CNT 90 modulation domain analy sis SW Cal certificate w protocol standard oscillator Cal certificate w protocol oven oscillator Cal certificate w protocol Hold over frequency ag ing week 3 years extended warranty 5 years extended warranty Getting Started Manual User s Manual Programmer s Handbook Specifications Timebase Options Product Family 9X Option Standard Option 19 90
19. 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 trigger 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 high sensitivity narrow hysteresis band to re duce the trigger uncertainty Triggering at or close to the middle of the signal leads to the How to Reduce or Ignore Noise and Interference 3 7 Input Signal Conditioning smallest trigger timing error since the signal slope is steepest at the sine wave center see Fig 3 15 When you ha
20. 6 5 Process 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 man 4 194 670 378 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 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 In all other behavior modes the LIM in 6 6 Limits 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 flashin
21. 8 4 Rise and Fall Time A B 8 4 Phase A Rel B BRel A 8 5 Duty FactorA B 8 5 Vmax Vmin Vpp A B ss eee ee eee 8 5 Timestamping A B C 8 6 Auto Set Manual Set 8 6 Input and Output Specifications 8 6 Inputs AandB 00 0 0 8 6 Input C Option 10 8 7 Input C Option 13 Lis 8 7 Input C Options 14 amp 14B 8 8 Rear Panel Inputs amp Outputs 8 8 Auxiliary Functions 8 8 Trigger Hold Off 8 8 External Start Stop Arming 8 8 Statistics cerne 8 8 Mathematics sre rere 8 9 Other Functions 8 9 DISDIAY PEN 8 9 GPIB Interface isle 8 9 USB Interface Re 8 10 TimeViewM la ro mee Ix opua 8 10 Battery Unit 2s primae 8 10 Option 23 90 lt carea opia 8 10 Measurement Uncertainties 8 11 Random Uncertainties 1c 8 11 Systematic Uncertainties 8 11 Total Uncertainty 20 8 11 Time Interval Pulse Width Rise Fall WMG sas CCHE ER Pc een a Frequency amp Period 8 11 Frequency Ratio fi fo 8 12 Phase sa bp teer ed 8 12 D ty Factor ie oben 8 12 Calibration oobis HRS ERES 8 12 Definition of Terms 8 13 General Specifications 8 13 Environmental Data 8 13 Power Requirements 8 13 Dimensions amp Weight
22. 90XL only Power up the instrument with the power cord disconnected The power supply status indicator next to the left of the charging level indicator in the upper right corner of the display shall now show a battery symbol It indicates that the internal battery is the active power source Press USER OPT 6G Misc and select Use Battery in Standby Yes to make sure the instrument will continue to oper ate in case line power fails If the charging level is above 60 let the instrument be running until the level goes below 60 Connect the power cord to the mains The status indicator shall now change to a charging battery symbol Let the battery charge for at least 8 5 h in normal operational mode When the specified charging time has elapsed the level indicator shall show a value close to 100 95 Disconnect the power cord and wait 10 s then reconnect the power cord The status indicator shall now show a power plug symbol on top of the battery symbol This means that the power line takes priority but will be replaced by the battery if the mains voltage drops out Note Charging will not be resumed until the level goes below about 70 in order to cycle the battery more efficiently Battery Supply 7 13 Performance Check Recall the default settings by pressing USER OPT Save Recall Recall Setup Default Connect 10 MHz OUT on the rear panel to Input A
23. 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 CNT 90 91 R With an optional prescaler the counter can measure up to 3 8 15 or 20 GHz on Input C Fig 4 1 Frequency is measured as the inverse of the time between one trigger point and the next fas t FREQ A B 4 3 Measuring Functions These RF inputs are fully automatic and no setup is required CNT 90XL The four versions cover the frequency ranges 27 40 46 and 60 GHz by means of an auto matic down conversion technique described on page 4 13 Faster manual acquisition is an alternative if the measured frequency is fairly known Then its nominal value can be entered via the keyboard as a fixed starting point for the acquisition process An additional feature is the possibility to mea sure signal power with high resolution RATIO A B B A C A C B To find the ratio between two input frequen cies the
24. 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 Dimensions amp Weight Width 75 x 19 210 mm Height 2E 90 mm Depth 395 mm Weight Net 2 7 kg 5 8 Ib Shipping appr 3 5 kg 7 5 Ib Ordering Information Basic Models CNT 90XL 27G 40G 46G 60G 400 MHz 100 ps Timer Counter including standard timebase and GPIB interface Included with In strument 18 months product war ranty line cord brochure with important informa tion getting started manual user s manual and programmer s hand book on CD Certificate of Calibration RF Input Variants 27G 27 GHz Input C 40G 40 GHz Input C 46G 46 GHz Input C 60G 60 GHz Input C Timebase Options Option 19 90 Option 30 90 Option 40 90 Medium stability OCXO Very high stability OCXO Ultrahigh stability OCXO 8 28
25. CNT 90XL General Specifications Optional Accessories Option 22 90 Option 23 90 Option 27 Option 27H Option 29 90 Option 90 01 Option 90 06 Option 90 00 Option 95 03 Option 95 05 Printed Manuals CNT 90 amp CNT 91 R amp CNT 90XL CNT 90 amp CNT 91 R amp CNT 90XL CNT 90 amp CNT 91 R amp CNT 90XL Rackmount kit Battery supply unit Carrying case Heavy duty hard trans port case TimeView modulation do main analysis SW for CNT 90XL Cal certificate w proto col standard oscillator Cal certificate w proto col oven oscillator Cal certificate w proto col hold over frequency aging week 3 years extended war ranty 5 years extended war ranty Getting Started Manual User s Manual Programmer s Handbook Specifications CNT 90XL Ordering Information 8 29 Specifications Timebase Options Product Family Option Option 19 90 Option 30 90 Option 40 90 Timebase Type OCXO OCXO OCXO Uncertainty due to Calibration adjustment tolerance 8 8 9 23 C 3 C lt 5x10 lt 1x10 3x10 Aging per 24 h 25x10 25x10 10 2 e3x10 10 per month lt 6x10 lt 1x10 8 3x10 per year 2x10 5x10 1 5x10 Temperature variation 0 C 50 C 5x10 5x10 2 5x10 20 C 26 C typ values 2x10 1x10 x10 9 Power voltage variation 10 5x1 o 5x1 o 5x1 g 9 Short term stability Root Allan Vari
26. Exit 0000 2 7 Presentation Modes 2 8 Entering Numeric Values 2 9 Hard Menu Keys 2 9 Default Settings 2 18 3 Input Signal Conditioning Input Amplifier 3 2 Impedance sslsslsssse 3 2 Attenuatiorii us Rete 3 2 COUPIING eiiean ae 3 3 Fillel 2 rer eere 3 3 Matn Auto cerne m 3 4 ALIQ gona healed acento EVE ae 3 5 How to Reduce or Ignore Noise and Interfereriee reaime a a ri ee 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 EREQ AV Bi siia Ree as 4 3 FREQ GC us he ax RE ER bd rena 4 3 CNT 90 91 R 2 eee eee eee 4 3 CNT 90XL 2 saint ok peated PERS 4 4 RATIO A B B A C A C B Ls 4 4 BURSTA B C 000 e eee 4 4 TAJEMNO s cee reme des 4 4 Burst Measurements using Manual Presetting 02 00055 4 5 Frequency Modulated Signals 4 6 Carrier Wave Frequency fo 4 6 MEE 4 7 fane dre ed be gp d dccus etse ossa 4 7 pv rrr 4 8 Errors in fmax fmin and Dipp 4 8 AM Signals ost 4 8 Carrier Wave Frequency 4 8 Modulating Frequency 4 9 Theory of Measurement 4 9 Reciprocal Counting 4 9 Sample Hold 4 10 TMe QUE Suec
27. Filter Digital LP Filter Trigger Indicators Max Voltage w o Damage 1 MQ 50 QO Input C Freq Range Read out on display 3 30 mV 15 150 mV 1 of trigger level Automatically set to 50 or 70 of input signal 10 and 90 for rise fall time Relative level in man ually adjustable when necessary Minimum hysteresis win dow compensation 70 and 30 of input signal Minimum hyster esis window if arming on A or B is activated gt 1 Hz default 100 Hz Nom 100 kHz RC type 1 Hz 50 MHz using trig ger hold off LED 350 V DC ACpk DC to 440 Hz falling to 12 VRMS x1 and 120 Vrms x10 1 MHz 12 VRMS 0 3 27 GHz 27G 0 3 40 GHz 40G 0 3 46 GHz 46G 0 3 60 GHz 60G SS CNT 90XL Operating Input Power Range 0 3 18 GHz 18 20 GHz 20 27 GHz 27 40 GHz 40 46 GHz 46 60 GHz AM Tolerance FM Tolerance Man Auto Impedance VSWR Max Power w o Damage O load indicator Connectors Notes Specifications 33 to 13 dBm 29 to 13 dBm 27 to 13 dBm 23 to 13 dBm 17 to 13 dBm 15 to 10 dBm Any modulation index as long as the minimum sig nal amplitude exceeds the sensitivity limit 50 MHZpp f gt 3 5 GHz 30 MHZpp f 3 5 GHz 20 MHZpp for modulation frequency gt 0 1 MHz 50 Q nom AC coupled lt 2 0 1 0 3 27 GHz typ lt 2 5 1 27 46 GHz typ lt 3 0 1 46 60 GHz typ 27
28. 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 If the 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 Vuax E Vum 2 Voc To display the rms value of a sine wave super imposed on a DC voltage follow the example above but set L Vpc 4 30 VRMS Measuring Functions Vrms 4 31 Measuring Functions This page is intentionally left blank 4 32 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 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 t
29. MHz However at these very high frequencies the phase resolution is reduced to 100ps x360 x FREQ What is Phase 4 21 Measuring Functions 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 channel 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 24 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 4 22 Possible Errors The trigger noise error consists of start and st
30. Note the polarity 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 W CNT 91R only While the rubidium oscillator is warming up an open padlock symbol labeled RB is flash ing at the top right corner of the display indi cating that the control loop is not locked Nor mal time to lock is about 5 min Do not start measuring until the unlock symbol disappears New Message Box Information exchange between the rubidium oscillator and the CPU takes place over a se rial bus Any malfunction in the UART con trolled communication link will be reported in a pop up message box on the display Wm CNT 90 XL w Option 23 90 The User Interface Screens have two indica tors near the upper right corner of the display One is a power supply status indicator and the other is a battery charging level indicator The status indicator shows e a fixed battery symbol when the internal battery is the active power source acharging battery symbol when the in ternal battery is being charged apower plug symbol when the mains is the active power source a power plug symbol on top of a battery symbol when the instrument has been prepared for UPS op
31. Range Storage Operating Time 25 C Charging Charging Time 25 C Status Indicator Weight Li lon 22 2 V 90 Wh 12 to 18 V max 6 A XLR male 3 pin 0 to 40 C 20 to 60 C 1 month 20 to 45 C 3 months 20 to 20 C 1 year ON gt 4 5 h Stby gt 24 h Automatic when ext AC or DC is connected lt 8 5 h On screen w low battery warning 1 2 kg Measurement Uncertainties Random Uncertainties 10 m Quantization Error Eq Eq 100 ps rms m Start Stop Trigger Error Ess 2 2 Ess Fhoise ES E jitter s l e RENE S NER noise input noise signal y l s inp sign slew rate A at trig point noise Ej Single Period Jitter rms s Vnoise input 500 uVrms internal noise 200 Vrms typical The rms noise of the applied signal Vnoise signal Systematic Uncertainties m Trigger Level Timing Error Et Time Interval Rise Fall Time Pulse Width Duty Factor Phase attenuator setting x1 E JLTLU 4 Hyst P OG Q6 IIs 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 6 mV 1 of trig lvl DC tol kHz for other measurement functions Specifications m Timebase Error TBE TBE is the relative error of the time
32. 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 over 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
33. are Description of Keys 2 9 Using the Controls Trigger Slope positive or negative indi cated by corresponding symbols Coupling AC or DC Impedance 50 O 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 Filter On or Off 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 10 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 Fig 2 10 Selecting analog or digital filter m input B The settings under Input B are equal to those under Input A m Settings This key accesses a host of menus that affect the measurement The figure above is valid af 2 10 Description of Keys ter changing the default measuring time to Frequency fi MEAS 10 000 040 61 mz Settings Burst Trigger Timebase MeasTime Hold Off Stat Ref Misc 10 ms off int Fig 2 11 The main settings menu 10 ms Meas Time Frequency A Meas 50
34. changes the frequency of the carrier wave The counter can measure fo Carrier frequency fmax Maximum frequency fmin Minimum frequency Df 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 Fig 4 6 Frequency modulation In the worst case exactly half a modulation cycle would be uncompensated for giving a maximum uncertainty of Minax tmeasuring x fo mod ulation X TU f n Snein For very accurate measurements of the carrier wave frequency fp 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
35. 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 41 for details 4 4 RATIO A B B A C A C B BURST A B C A burst signal as in Fig 4 4 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 400 MHz Burst measurements on Input C in volve prescaling so the minimum number of 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 e
36. 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 Measuring Functions m Low Modulation Frequencies Press SETTINGS STAT and make the No of samples parameter as large as possible considering the maximum allowed measure ment time Press STAT PLOT and let the 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 Dfmax 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 lower than fp The statisti cally averaged value of the frequency fmean approaches fo 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 alae where n is the number of averaged samples of f XA finax fmax Press SETTINGS STAT and set No of samples to 1000 or more Press Meas Time and select a low val
37. 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 2 Press Start Delay and enter a value lon ger than the transient part of the burst pulse Measuring Functions Select Frequency Limit 160 400 MHz if Input A or Input B is to be used Use Fig 4 2 Set the sync delay so that it ex pires in the gap between the bursts 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 Arm rn delay Measuring time j i i Burst Sync delay Fig 4 3 Three time values must be set to measure the correct part of a burst m Selecting Measurement Time 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 only 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 BURST A B C 4 5 Measuring Functions m How Does the Sync Delay Work The sync delay works as an internal start a
38. 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 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 MATH LIM menu to enter this value as the constant L in the for mula K X L by pressing Xo and change sign 4 24 Possible Errors frequency or the amplitude changes Systematic trigger level timing 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 devia
39. prohibited when Setup Protect is ON Switching OFF Setup Protect releases all ten memory positions si multaneously Fig 2 29 CNT 90XL amp CNT 90 with m id Option 23 90 The User Options The different setups can be individually la menu beled to make it easier for the operator to re member the application Frequency fi Meas Frequency A MATH MEAS 3 333 999 999 B wz 20 000 001 77 mz User options User options Save Recall Hx ee Set s EAE ae alte Recall Modify protact Recall Interface 0 About setup tabata Un Fig 2 30 CNT 91 R The User Options Fig 2 32 The memory management mentis menu after pressing Setup From this menu you can reach a number of The following can be done submenus that do not directly affect the mea Save current setup surement Frequency fi Meas You can choose between a number of modes by pressing the corresponding softkey 2 14 Description of Keys 90 000 001 77 mz User options Save Recall Save current setup 2 3 4 8 Next Selecting memory position for saving a measurement setup Fig 2 33 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 fi Meas 50 000 001 76 mz User options Save Recall Recall se
40. resolution of 100 ps independent of the mea sured frequency Consequently the use of prescalers does not influence the quantization error Therefore the relative quantization error is 100 ps tg For a 1 second measurement time this value 1S 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 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 time out 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 Measuring Functions When no triggering has occurred during the Function Prescaling time out the counter will show NO SIGNAL Factor FREQ A B 400 MHz 2 Measuring Speed BURST A B 160 MHz 1 The set measurement time determines the BURST A B 160 MHz 2 measuring speed for those functions that uti lize averaging Frequency and Period PERIOD A B AVG 400 MHz 2 PERIOD A B SGL
41. signals during extended periods of time Monitoring distrib uted PLL clocks in synchronous data trans mission systems is a typical application The frequency of the signal to be checked can be either manually or automatically set Auto detects the frequency from the first two sam ples The value is rounded to four digits e g 2 048 MHz and is output on the bus when a query is sent It is also displayed as an auxil iary parameter in VALUE mode TIE is measured as the time interval between the input signal and the internal or external timebase clock These signals are not phase locked so irrespective of the real time interval value at the start of a measurement the result at t 0 is mathematically nulled Thus the graphic representation in STATIS TICS mode starts at the origin of coordinates Rise Fall Time A B These functions can be found under the func tion menu Time 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 Time Interval 4 17 Measuring Functions start and 90 stop of the maximum pulse amplitude see Figure 4 16 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 Fig 4 16 Tri
42. 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 50 000 001 76m Trig 2 45_ U mu 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 over 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 level
43. the measurement speed at the expense of accuracy TIE CNT 91 only From a submenu you can either let the counter choose the reference frequency automatically Auto or enter it manually m Math Limit Frequency A Meas 50 000 001 77 wi zc Limits Fig 2 23 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 emas 4 194 673 693 mz Math Limit Math Math K L M Off 1E0 0 EO 1E0 Fig 2 24 The Math submenu The Math branch is used for modifying the measurement result mathematically before presentation on the display Thus you can 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 Frequencu fi WEAR 4 222 931 8B mz Math Limit Math Math Off K W4L KL M M xIM 1 Fig 2 25 Selecting Math formula for postprocessing Using the Controls The display tells you that the Math function is not active so press the Math Off key once to open the formula selection menu Select one of the five different formulas where K L and M are
44. the number of cars passing the entrance A gate minus the ones passing the exit B gate TOT A B MAN This mode enables you to calculate the ratio of trigger events on Channel A and Channel B Auxiliary parameters are A and B Start Stop is manually controlled by toggling the key HOLD RUN and the counting regis ters are reset by pressing RESTART Totalize amp Arming By using Arming together with Totalize you can open and close the gate with an external signal applied to one of the channels A B or 4 26 TOT A B MAN E In this way you can realize a host of func tions like TOT A START STOP by B TOT A B Gated by E and TOT B Timed by A simply by selecting channel slope and delay time for Start Stop Unlike the manual Totalize functions the armed variants resemble the other measure ment functions inasmuch as they allow block and pacing control Consequently all the Sta tistics functions are available A new result is displayed after each stop condition Examples The comprehensive Arming features can be found under SETTINGS Arm In order te set up the Totalize functions above do the following m TOT A START STOP by B Select Totalize from the MEAS FUNC menu and then A Connect the signal to be measured to Input A Set the trigger level for Input A manually to a suitable value Connect the control signal to Input B Set the trigger level for Input B manually to a suitable val
45. 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 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 Vpp VIN 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 Performance Check Trigger Indicators vs Trigger Levels Trigger Level manually set Trigger Indicator Pass Input A Input B 1V off 1V on 0 0 V 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 tr
46. 00 MHz 3 0 GHz 16 20 mVrms 12 Vrms 10 mVrms 12 Vrms 20 mVrms 12 Vrms 40 mVrms 12 Vrms Amplitude Modulation DC 0 1 MHz Modulation Frequency 0 1 6 MHz Modulation Frequency Impedance Max Voltage w o Damage Connector Up to 94 depth Up to 85 depth Min signal must exceed min oper input voltage 50 Q nom AC coupled VSWR lt 2 5 1 12 Vrms PIN diode prot Type N female Input C Option 13 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 depth Up to 85 depth Min signal must exceed min oper input voltage 50 Q nom AC coupled VSWR 2 5 1 7 Vrms PIN diode protected Type N female CNT 91 R Specifications Input C Options 14 amp 14B Freq Range 250 MHz 15 GHz 14 250 MHz 20 GHz 14B Prescaler Factor 128 Operating input voltage range 0 25 0 5 GHz 21 to 27 dBm 0 5 15 GHz 27 to 27 dBm 14 18 GHz 27 to 27 dBm 14B 18 20 GHz 21 to 27 dBm 14B AM tolerance Up to 90 depth Burst Minimum Burst Length Period x 257 Minimum Interval Between Bursts 10 us Impedance
47. 0XL 000 7 13 Prescaling effect Of oliv ls vie RI Be 4 11 Processing a measuring result 6 2 Profiling i 22 P8245 hark etre 5 9 5 13 transient sss 5 14 VCO step response 5 14 Pulse period 04 4 13 Pulse rounding 4 18 Pulse Width description 4 17 R Rate of measurement 5 5 Ratio FUNCOM uox e eer aom wat 4 4 Reciprocal counting 4 9 Reference oscillators CHECKING uen Rr 7 8 ISeStart 2 522 Ly petes UH dg 5 2 RF Inputs checking 7 12 Rise Falltime corr 4 16 Rubidium oscillator checking 7 8 S Sample Hold 4 10 Sensitivity 4 18 checking 7 5 Setup time forarming 5 9 Single 2 200000 ee 4 10 Single shot phenomena 5 6 Smart Frequency 2 12 Smart Time Interval 2 12 Speed ARMING SPP 5 9 of measurement 4 10 Standard deviation 6 3 Start AMN gesce ae tals ea pdt a 5 2 5 6 of ameasurement 5 4 Statistics coelum 6 3 and Mathematics together 6 5 Stop ARMING uoce ead ae 5 2 5 6 of measurement 5 5 Synchronization of a measurement 4 11 Syncronization delay arming sucesor 5 7 Systematic errors in phase measurements 4 22 T TIE4 16 MME cies seats Seon vie
48. 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 amp Vpp 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 VMrN 0x 0 015 V and VMAX 0 0 015 V Adjust the current limit for the voltage source to 200 mA Connect 42 500 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 Vmax 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 MO 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 450 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 7 6 Short Form Specification Test Press INPUT A and select 1x Press EXIT OK Connect a sinusoidal signal to Input A
49. 400 MHz 1 FREQ C 3 GHz 16 FREQ C 8 GHz 256 FREQ C 15 amp 20 GHz 128 All other functions 1 Fig 4 11 Divide by 16 Prescaler Table 4 1 Prescaling factors Awg For continuous signals Speed readings s be when Auto trigger is on and can be increased to Speed readings s 0 001 when Manual trigger is on or via GPIB Speed readings s p tg 0 00012 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 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 m CNT 90 91 R Prescaling May Influence Measurement Time Prescalers do affect the minimum measure ment time inasmuch as short bursts have to contain a minimum number of carrier wave periods This number depends on the prescalin
50. 50 MHz and is divided into a number of dis crete frequencies fetched from a look up table The LO output is fed to a comb gen erator that creates a harmonic spectrum covering the whole specified microwave range The automatic process of calculating the input frequncy consists of the following Steps Preacquisition The purpose of this process is to find WAVE y f INPUT gt MIXER E SIGNAL DETECTOR BASE UNIT d IF AMPLIFIER 10 200 MHz COUNTER i i i t COMB i GENERATOR i LOCAL A MEMORY f i i 4 l nf PWR METER VIF CONV LO SYNTH HEROG 10 MHz REF out if there is a measurable signal pres ent at the input and if so fix the LO frequency that gives rise to an IF sig nal above a certain threshold level This is done by sequentially stepping the LO from the highest value in the look up table to the lowest value and applying the resulting comb generator spectrum to the mixer The process is stopped when the signal detector outputs a status signal to the processor Fig 4 14 Microwave acquisition in the CNT 90XL desired resolution and then the result is used for calculating the final value to be presented on the display as f fio IF There are a number of conditions that can complicate the acquisition process All of t
51. 50 O nom AC coupled VSWR lt 2 1 Max Voltage w o Damage 27 dBm PIN diode prot Connector Type N female Rear Panel Inputs amp Outputs Ref Input 1 5 or 10 MHz 0 1 5 Vrms sinewave impedance gt 1 kQ Ref Output 1x10 MHz gt 1 Vrms into 50 Q load Arming Input E Arming of all meas func Freq Range DC 80 MHz Trigger Level TTL 1 4 V nom Trigger Slope Positive or negative Meas Inputs A B C option Impedance 1 MQ 50 pF or 50 Q VSWR 2 1 Input and Output Specifications 8 37 Specifications Pulse Output Mode Pulse Out Gate Open Alarm Out Period 20 ns 2 s in 10 ns incr Pulse Width 10 ns 2 s in 10 ns incr Output Level TTL levels in 50 Q 2 ns rise time Connectors BNC SMA for Input C 8 38 CNT 91 R Auxiliary Functions Auxiliary Functions Trigger Hold Off Time Delay Range 20 ns 2 s 10 ns resol External Start Stop Arming Modes Start arming stop arming start and stop arming Input Channels A B E EXT ARM Max Rep Rate for Arming Signal Channel A B 160 MHz Channel E 80 MHz Start Time Delay Range 10 ns 2 s 10 ns resol Stop Time Delay 20 ns 2 s 10 ns resol Range Stop Time Delay can only be used in conjunction with the non manual Totalize Functions Statistics Functions Maximum minimum mean Dmax min standard deviation Allan deviation Display Numeric or numeric graphic Graphic Histogram amp tr
52. 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 connected 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 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 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 Fig 1 5 Fold down support for comfort able bench top use Rackmount Adapter 210mm ager 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 rackm
53. C 4600 m Max Altitude Random and sinusoidal per Vibration MIL PRF 28800F Class 3 Half sine 30G per Shock MIL PRF 28800F bench handling Transit Drop Test 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 CNT 91R only CNT 91 R Calibration 8 43 Specifications Reliability Safety 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 EMC EN 61326 1997 A1 1998 increased test levels per EN 50082 2 Group 1 Class B CE Power Requirements Line Voltage Power Consump 90 265 Vrms 45 440 Hz tion CNT 91 40 W CNT 91R 60 W Dimensions amp Weight Width 75 x 19 210 mm Height 2E 90 mm Depth 395 mm Weight CNT 91 Net 2 7 kg 5 8 Ib CNT 91R Shipping 3 5 kg 7 5 Ib 8 44 CNT 91 R Ordering Information Ordering Information Basic Models CNT 91 400 MHz 50 ps Timer Counter including standard timebase and GPIB interface CNT 91R 400 MHz 50 ps Timer Counter including rubidium timebase and GPIB interface Included with In strument 18 months product war ranty line cord brochure with important information getting started manual user s manual and pro grammer s handbook on CD Certificate of Calibra tion RF Input Op
54. D DC coupling 004 3 3 Delay arming sync 5 7 Delayed timebase 5 3 Digits Blank 2 16 Display contrast adjusting 2 7 DIStOMION 1s ug Ege ot eich 3 8 Dattan Deest pt deem E 6 4 See Also Long time instability Drift measurements 5 13 Duty cycle See Duty factor E End ofa measurement 5 4 Erroneous counts 3 7 Error NO TRIG 4 10 Examples armillqus suus cue Edu 5 9 Ext Arm Input Checking 7 10 External gate 5 6 F Filter analog cose rmm n 3 3 Fixed trigger levels 3 5 EM Signals ir eue atest ae Meek 4 6 Free running measurements 5 4 5 13 Freezing the display See hold run Frequency inaa ure steeds 4 3 back to back 0 4 14 b tst exon tee ped EE ED 4 4 modulated signals 4 6 range test 2 7 5 alios axe okt bene eke eee E 4 4 Frequency versus time See Profiling Function penodi oaei p 4 13 PATO 6 d acp a aed aed heen 4 4 Index G Gate indicator se eee 5 2 H Harmonic distortion 3 8 Hold ssi op icmsiiadou dd di adeda dhs 5 6 Hold Off checking 7 10 used as filter 0 3 4 Hysteresis 3 6 4 18 Input C checking 7 12 Input C Acquisition 2 12 Inst
55. Hz 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 CNT 90 8 GHz Option Frequency Amplitude P F GHz mVrus dBm 0 2 0 5 20 21 0 5 15 10 27 Table 7 10 RF input sensitivity CNT 90 15 GHz Option Frequency Amplitude P F GHz mVrus dBm 0 2 0 5 20 21 0 5 18 10 27 18 20 20 21 Table 7 11 RF input sensitivity CNT 90 20 GHz Option Frequency Amplitude P F GHz mVrms dBm 0 3 18 5 33 18 20 8 29 20 27 10 27 27 40 16 23 40 46 32 17 46 60 40 15 Notes not CNT 90XL 27G not CNT 90XL 27G 40G not CNT 90XL 27G 40G 46G Table 7 12 RF input sensitivity CNT 90XL Power Measurement CNT 90XL only Apply signals according to Table 7 13 from a well calibrated signal generator to Input C and read the power level It is displayed as an auxiliary parameter below the main frequency parameter Check the results against the toler ance levels NOTE The indicated tolerances are only typical Use short high quality coaxial cables to avoid signal loss Freq Power dBm P F GHZ Appl Displ Tol 27 20 20 1 40 15 15 2 46 10 10 2 60 5 5 3 Table 7 13 Power measurement CNT 90XL Performance Check Battery Supply Option 23 90 for CNT 90 amp CNT
56. LD 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 SESHPEOT 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 Select 50 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 O 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
57. 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 Frequency Ratio fA fg or fa fa m Typical Random Uncertainty rms NOTE Frequency Ratio is an auxiliary mea surement function intended to give an indica tion with no guaranteed specification U ma 2 x presc fact x fi x EZ Esm Esm dimensionless e g ppm fj is the higher of the two frequencies Uic VK TBE MR 200 ps MT MR Hz or s where MR Meas Result Freq or Per MT Meas Time Frequency amp Period C m Random Uncertainty rms 2 2 Une 88 2522 MT MT where F Meas Result expressed as frequency rounded up to the nearest whole GHz Example 14 2 GHz should be inserted as 15 10 m Systematic Uncertainty Us sene FY 4 d 3 MT F is calculated as under Random Uncertainty above Prescaling Factor 2 A amp B Input Frequency Ratio fc f or fc fp NOTE See preceding note m Typical Random Uncertainty rms Uma 4 foor fe 25psy fizs Ey 2E where Eug Trigger Error Phase m Typical Random Uncertainty rms NOTE Phase is an auxiliary measurement function intended to give an indication with no guaranteed specification Uma ze Strt Trg Err Stop Trg Err x xFreq x360 m Systematic Uncertainty Una LE
58. T Up to 8 different datasets can be saved in FLASH memory each containing up to 32000 sam ples If the pending measurement has more than 32000 samples only the last 32000 will be saved A default label will be assigned to the dataset It can be changed in a similar way as the setup labels See Modify labels above Save Select a memory position accept or change the name and press OK Recall Select a memory position and press OK Total Reset The safety screen below will appear Pressing OK will restore all factory set tings and erase all user information This will reset settings to default erase all Saved data including protected setup and measurement results and reboot the instrument Would uou like to continue OK Cancel Fig 2 37 The Total Reset safety screen Calibrate Menu This menu entry is accessible only for calibra tion purposes and is password protected Description of Keys 2 15 Using the Controls Interface Menu Frequency A mas 4 134 667 535 mz User options Interface GPIB Bus Type GPIB Mode Address GPIB Native 10 Fig 2 38 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 GPIB Mode There are two command systems to choose from Native The SCPI command
59. Timer Counter Analyzer CNT 90 CNT 91 Frequency Calibrator Analyzer CNT 91R Microwave Counter Analyzer CNT 90XL User s Manual 4031 600 90001 May 2011 Sixteenth Edition 2011 Spectracom 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 2c cece eee eee Introduction 2 ci a sel Powerful and Versatile Functions No Mistakes 000 Design Innovations State of the Art Technology Gives Durable Use Safety Precautions Caution and Warning Statements Symbols 41 53 9x vv re 8a epu qu If in Doubt about Safety Disposal of Hazardous Materials Unpacking Check List cem mmm Identification Installations 4x mn Supply Voltage Battery Supply Grounding Orientation and Cooling Fold Down Support Rackmount Adapter 2 Using the Controls Basic Controls 2s era Rte Secondary Controls 1 2 1 3 1 3 1 7 1 8 1 8 1 8 1 8 1 9 Ill Connectors amp Indicators 2 4 Rear Panel er dee 2 5 Description of Keys 2 6 POWER osse ated ee e Rem 2 6 Select Function enr nh 2 6 Autoset Preset lee eee 2 7 Move Cursor 6 0 002 eee 2 7 Display Contrast 2 7 ENGR esrb rem dla atte 2 7 Save amp EXit 5 oot edat 2 7 Don t Save amp
60. a ter ep RET ERIS 4 10 Measuring Speed 4 10 PERIOD niria os n EAE 4 13 Single A B amp Avg A B C 4 13 Single A B Back to Back 4 14 Frequency A B Back to Back 4 14 Time Measurements 4 15 Introduction eaei omaes 4 15 Triggering piscinei ie nea 4 15 Time Intervals iaaea me 4 16 Time IntervalAtoB 4 16 Time IntervalBtoA 4 16 Time IntervalAtoA BtoB 4 16 CNT 91 R Time Interval Error TIE 4 16 Rise Fall Time A B 0 4 16 Pulse Width A B 000 5 4 17 Duty Factor AJB 2 2 siccae 4 17 Measurement Errors 4 18 Hysteresis souc erea exe 4 18 Overdrive and Pulse Rounding 4 18 Auto Trigger esar e eenei 4 19 Ph S6 bie eenia at 4 20 What is Phase 4 20 Resolution sean eee ok oes 4 20 Possible Errors 0 55 4 20 Inaccuracies issus 4 21 Totalize CNT 91 R only 4 24 Totalize in General 4 24 TOTAMAN eeeee A 4 24 TOT B MAN rne ves 4 24 IV TOT A B MAN 000005 4 24 TOTA BMAN seesese nen 4 25 Applications 4 25 TOTA BMAN 02000 eee 4 25 Totalize amp Arming 4 25 Example S ses as tu ona ae 4 25 Voltage eR IIR 4 28 XM MAX VMIN VBPs a eee mane donee dm 4 28 M ES svedese a certes eit ei Sh eee 4 29 5 Measurement Control About This C
61. ability 2 iere 6 4 Internal reference output checking 7 9 Interpolatator Calibration 2 12 J Jer seve cae om DEN OT ERE 6 4 LCD contrast adjusting 2 7 EMIS ye ue ox Ye eh 6 6 LOCALLOCKOUT mode 2 7 LOCAL mode i ore iren aeie neia et 2 7 Long time instability 6 4 Low pass filter digital eie aenn eee es 3 4 M Manual arming lllls elles 5 6 E M Index Mathematics and Statistics together 6 5 constants slc oou 6 2 example lsuss 6 2 TUNCUOMN NEP 6 2 Mean us ace sa abe eink Ree Sad E 6 3 Measurement end rios eee dee bs 5 4 free running 5 13 dle cos VERAM EDS ES 5 5 Start leloelsnLEes lausda 5 4 TIMING 2s ELE ERDeE Eee 5 4 Measurement Errors 4 18 Measurement rate 6 4 Measurement time setting uie edes 5 2 Measuring speed 4 10 6 4 Measuring time 5 5 influence by prescaling 4 11 MISC ostii deca o cera hen ee do 2 16 Modulating frequency AM 4 9 Monitoring 6 2 N No trig display message 4 10 NOISE ie Rp Reb E Rs 3 6 O Output isse Redes 2 17 Overdrive 220000055 4 18 P Period use eo eee ek es 4 13 single amp average 4 13 single back to back 4 14 PASC ian aae ERR Rb 4 20 inaccuracies 4 21 Power Measurement CNT 9
62. ach 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 6 may 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 Fig 4 4 Burst signal Burst Measurements using Manual Presetting You can measure the frequency on Input A and Input B to 400 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 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
63. 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 Description of Keys 2 7 Using the Controls Presentation Modes m VALUE Frequency A Meas 90 000 001 76 mz Umax 1 462 dU Umin 2 528 4 U Up p 3 990 8 U Fig 2 4 Main and aux parameters Value mode gives single line numerical pre sentation of individual results where the main parameter is displayed in large characters with full resolution together with a number of aux iliary parameters in small characters with lim ited resolution Frequency A MEAS 43 333 333 2m MHz 49 900 000 000MHz Umax 1 490 U Umin 2 529 U 50 100 000 000MHz Up p 4 019 U Fig 2 5 Limits presentation If Limit Behavior is set to Alarm and Limit Mode is set to Range you can visualize the de viation o
64. all time Min Amplitude 100 mVp p m Display Main Parameter Rise or fall time Aux Parameters Slew rate Vmax Vmin CNT 91 R Measurement Functions 8 33 Specifications Time Interval Error TIE A B Normalized Period Back to Back measure ments calculated as k TIE k k xTrer X Ti iA Ti individual period back to back and TREF reference period value Range Resolution Freq Range Signal Type Mode Auto Mode m Display Main parameter Aux parameter 1x107 s 50 ps rms typical 1 Hz to 250 MHz Clock only Auto or manual freq set Measures freq of the first two samples rounded to 4 digits TIE value Clock signal frequency Phase A Rel B B Rel A Range Resolution Input Frequency Min Pulse Width 180 to 360 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 Up to 160 MHz 1 6 ns Smart Calculation One pass meas of time interval single period between two continuous signals with frequency f1 amp f2 where f4 f2ZN or N N is an integer The meas is made with 4 time stamps 2 consecu tive trig A two consec utive trig B to determine sign of phase m Display Main Parameter Phase Aux Parameters Freq prim channel VA NB in dB based on peak to peak meas Duty Factor A B Range 0 000001 to 0 999999 Input Frequency 0 1 Hz 200 MHz Min Pulse Wid
65. ance t 1s lt 1x10 1x101 5x101 Typical values t 10 s 1x10 7 1x10 5x10 Power on stability E E P Deviation versus final value after 24 h 1x10 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 2c 95 confidence interval 3 8 8 1 year after calibration 2 4x10 lt 6x10 lt 1 8x10 2 years after calibration 4 6x10 7 12x107 3 6x10 Typical total uncertainty for op erating temperature 20 C to 26 C 2c 95 confidence interval 7 8 3 1 year after calibration lt 2 4x1 o 6x1 0 lt 1 7x1 0 a 2 years after calibration lt 4 6x10 lt 1 2x10 lt 3 5x10 Explanations 1 Standard timebase oscillator in the CNT 90XL 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 OCXO Oven Controlled Crystal Oscillator 8 30 CNT 90XL Timebase Options Specifications CNT 91 R CNT 91 R Timebase Options 8 31 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 11 for uncertainty informa tion Inputs A and B can be swapped in all modes except Rise Time and Fall Time Display All measurements are
66. anual 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 integration 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 charg
67. art arming delay Functions Frequency in burst Hz PRF Hz Number of cycles in burst Range A B See Frequency A B Min Burst Duration 40 ns 80 ns 160 MHz Min No of Pulses in Burst 3 6 above 160 MHz PRF Range 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 CNT 90XL Introduction 8 17 Specifications Period A B m Range Input A B Input C 27 GHz 40 GHz 46 GHz 60 GHz Acquisition Acquisition Time Resolution m Display Input A B Main Parameter Aux Parameters Input C Main Parameter Aux Parameter C Average 3 3 ns 500 s 37 ps 3 3 ns 25 ps 3 3 ns 22 ps 3 3 ns 17 ps 3 3 ns Auto or Manual within 40 MHz 25 ms in Auto typ 12 digits s Period Vmax Vmin Vp p Period Power in dBm Period A B Single Range A B Resolution m Display Main Parameter Aux Parameters 3 3 ns 1000 s 100 ps Period Vmax Vmin Vp p Ratio A B B A C A C B Range Freq Range A B Freq Range C 10 to 10 one pass measurem values 1 with reduced resolution 100 Hz to 400 MHz Full input C range m Display Main Parameter Aux Parameters Ratio Freq 1 Freq 2 Time Interval A to B B to A Ato A BtoB Range normal calculation Range smart calculation Resolution Sing
68. ate Stop Delay Decide if you need to insert a delay 10 ns 2 s during which the gate will not respond to the control signal on the Stop Channel The main application is to prevent relay contact bounces from closing the gate prematurely Stop Channel Select E Stop Slope Select NEG marked by a falling edge symbol W TOT B Timed by A Select Totalize from the MEAS FUNC menu and then B Connect the signal to be measured to In put B Set the trigger level for Input B manually to a suitable value Connect the control signal to Input A Set the trigger level for Input A manually to a suitable value Go to the Arming menu SETTINGS Arm and set the six parameters Arm on Sample Block Decide if each event or each block of events STATISTICS mode should be armed Start Channel Select A Start Slope Select POS marked by a rising edge symbol Start Delay Decide if you need to insert a delay 10 ns 2 s between the control signal and the actual opening of the gate Totalize amp Arming 4 27 Measuring Functions Stop Delay Set the measurement time between 10 ns and 2 s Stop Channel Select Time With this function you can synchronize the start of an accurate gate time to an external event 4 28 Totalize amp Arming Voltage VMAX VMIN VPP Measuring Functions Press MEAS FUNC Volt The counter can measure the input v
69. ation 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 CNT 90 Timebase Options 8 15 Specifications CNT 90XL 8 16 CNT 90XL 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 25 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 Hz 400 MHz Input B 0 002 Hz 400 MHz Input C 0 3 27 GHz CNT 90XL 27G 0 3 40 GHz CNT 90XL 40G 0 3 46 GHz CNT 90XL 46G 0 3 60 GHz CNT 90XL 60G Acquisition Time 25 ms in Auto typ Resolution 12 digits s Specifications m Display Inputs A amp B Main Parameter Frequency Aux Parameters Vmax Vmin Vp p Input C Main Parameter Aux Parameter Frequency Power in dBm Frequency Burst A B Frequency and PRF of repetitive burst signals can be measured without external control sig nal and with selectable st
70. base oscil lator dimensionless and depends on the ac tual oscillator used See Timebase Options on page 8 15 Total Uncertainty 2c The general formula for all measurement functions is Uv 2 il rand uncert Y syst uncert Time Interval Pulse Width Rise Fall Time m Random Uncertainty rms U nd Eden Error StopTrig Error s m Systematic Uncertainty Us VK Ev 500 ps 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 200 ms and if Smart Freq AUTO or OFF 2 fe 2 Start Trigger Error x U rnd F 2 Measuring Time x Measurement Result Hz or s CNT 90 Measurement Uncertainties 8 11 Specifications For measuring times gt 200 ms and if Smart Freq AUTO or ON 2s E 2 Start Trigger Error U 9 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 Uic VK 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 specifica
71. 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 power 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 CAUTION Shows where incorrect procedures can cause damage to or destruction of equipment or other property WARNING Shows a potential danger that requires correct proc
72. c Range x1 30 mVp p to 10 Vp p within 5 V window 8 6 CNT 90 Input and Output Specifications Specifications 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 Auto Hysteresis Time Meas Minimum hysteresis win dow compensation Freq Meas amp Per Avg 70 and 30 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 Ma 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 Option 10 100 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 CNT 90 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 Max Voltage w o Damage 12 Vrms PIN diode prot
73. ccuracy of the CNT 91R an extremely high stability reference signal is needed Examples of such references are Ce Oscillator Frequency Readout Suitable Reference P F Standard UCXO 10 00000000 MHz 150 Hz 6688 Option 30 90 OCXO 10 00000000 MHz 1 Hz 6689 Option 40 90 OCXO 10 00000000 MHz 0 25 Hz 6689 Table 7 6 Acceptance test for oscillators 7 8 Short Form Specification Test sium Atomic references or transmitted signals from a nationally or internationally traceable source e g GPS controlled reference oscilla tors See the table below Recommended Test Equipment Type Stability Model 10 MHz 1x101 Pendulum GPS 89 or ultrastable Fluke 910R or Pen reference dulum GPS 12Rwith satellite contact dur ing the last 72 hours Test procedure Connect the counter to line power Check that the UNLOCK indicator turns on and then turns off again within 6 min utes after connecting line power Connect the 10 MHz reference signal to input A of the counter Select function FREQ A Select Meas Time 2 s Check that the displayed frequency is 10 00000000 MHz 0 1 Hz less than ten minutes after connection to line power 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 othe
74. constants that the user can set to any value X stands for the current non modified measurement result Frequency fi nama nena 00 975 813 646 mz Math Limit Math Math K L M K X LY M 1E0 0 EO 1E0 Fig 2 26 Selecting formula constants Each of the softkeys below the constant labels opens a value input menu like the one below 80 000 001 76 we K DEE 0 EE Xo Fig 2 27 X Entering numeric values for constants 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 The Limit submenu is treated in a similar way and its features are explored beginning on page 6 6 Description of Keys 2 13 Using the Controls m User Options Save Recall Menu Frequency A maa 10 000 000 000 4 mz User options Frequency A nam X30z MEAS 290 034 429 23 m User options Save Recall Calibrate Test Digits Save Blank Total Interface 0 About Dataset Reset Fig 2 28 CNT 90 The User Options Fig 2 31 The menu appearance after menu pressing Save Recall Twenty complete front panel setups can be Frequency A nur FERDEN stored in non volatile memory Access to the 248 027 886 883 m User options Calibrate Test Digits Save Blank Recall Interface 0 About first ten memory positions is
75. cs 6 7 7 Performance Check General Information 7 2 Preparations 00000 7 2 Test Equipment 7 2 Front Panel Controls 7 3 Internal Self Tests 7 3 Keyboard Test 5 7 3 Short Form Specification Test 7 5 Sensitivity and Frequency Range 7 5 VONAGE eie as 7 6 Trigger Indicators vs Trigger Levels 7 7 Input Controls canens 7 8 Reference Oscillators not CNT 91R 7 8 Rubidium Oscillator CNT 91R 7 8 Resolution Test 7 9 Rear Inputs Outputs 7 9 TO MEIz QUT zr Rm 7 9 EXT REF FREQ INPUT 7 9 EXT ARM INPUT 7 10 Measuring Functions 7 10 Check of HOLD OFF Function 7 10 RFInputs usine duree des 7 12 Checking InputC 7 12 Power Measurement CNT 90XL only 000 7 13 Battery Supply 7 13 Option 23 90 for CNT 90 amp CNT 90XL ONIY t a deias a aiaa Rb REX eS 7 13 8 Specifications CNT 90 oco RR x n 8 2 Introductio 1 cue 8 3 Measurement Functions 8 3 Frequency A B C 8 3 Frequency BurstA B C 8 3 Period A B C Average 8 3 Period A B Single 8 4 Ratio A B B A C A C B 8 4 Time Interval A to B B to A Ato A Bio Bonnae cea taa A eek 8 4 Pulse WidthA B
76. ctors like the speed of the GO detec tor This speed depends on the specific input option used WB CNT 90XL Microwave Conversion Measuring frequencies up to 20 GHz is possi ble with the top performance prescaler option 14B The general principles of prescalers are described in the preceding paragraph The different versions of the CNT 90XL are intended for applications with upper fre quency limits between 27 GHz and 60 GHz Here another technique is utilized downconversion by means of mixing the un known signal with known LO frequencies un til there is a signal present within the passband of the IF amplifier in this case 10 200 MHz A simplified block diagram can be seen in Fig 4 14 Measuring Functions Acquisition We don t know yet which harmonic gener ates the IF signal First we measure the IF with the counter Then we decrease the LO frequency by 1 MHz and measure the IF once more If for instance the difference between the two values is 5 MHz then we know that the fifth harmonic is the origin By examining the sign of the difference we can decide if the original IF should be added to or subtracted from the calculated harmonic in order to arrive at the final value Final RF calculation Now we know the LO frequency the mul tiplication factor n and the sign What re mains to be done is to count the IF during a measurement time corresponding to the The basic LO frequency range is 430 5
77. dBm not 60G 25 dBm 60G ON Pin gt 10dBm SMA 27G 2 92 mm 40G amp 46G 1 85 mm 60G not CNT 90XL 27G 2 not CNT 90XL 27 40 G 3 not CNT 90XL 27 40 46 G all field replaceable female sparkplugs Rear Panel Inputs amp Outputs Ref Input Ref Output 1 5 or 10 MHz 0 1 5 Vrms sinewave impedance gt 1 kQ 1x10 MHz gt 1 Vrms into 50 Q load Input and Output Specifications 8 21 Specifications Arming Input E Arming of all meas func HH Freq Range DC 80 MHz Auxiliary Functions Trigger Level TTL 1 4 V nom Trigger Slope Positive or negative Tri g g er H ol d Off Time Delay Range 20 ns 2 s 10 ns resol External Start Stop Arming Modes Start arming stop arming start and stop arming Input Channels A B E EXT ARM Max Rep Rate for Arming Signal Channel A B 160 MHz Channel E 80 MHz Start Time Delay Range 10 ns 2 s 10 ns resol NOTE Stop arming has no delay setting Statistics Functions Maximum minimum mean Dmax min standard deviation Allan deviation Display Numeric or numeric graphic Graphic Histogram amp trend plot auto scaled Sample Size 2 to 2 x 10 Max Sample Rate 250 kSa s measured 2 kSa s calculated depending on meas func tion and graphics 8 22 CNT 90XL Auxiliary Functions Limit Qualifier Meas Pacing Off Capture amp store values above limit 2 Capture amp store values below l
78. 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 0 001 Hz 400 MHz Input B 0 001 Hz 400 MHz Input C 100 MHz 3 GHz Opt 10 300 MHz 8 GHz Opt 13 200 MHz 15 GHz Opt 14 200 MHz 20 GHz Opt 14B Resolution 12 digits s smart frequency 11 digits s normal and back back m Display Main Parameter Frequency Aux Parameter A B V max Vmin Vp p 8 32 CNT 91 R 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 15 GHz 72 ps 5 ns 20 GHz 50 ps 5 ns Resolution 12 digits s m Display Main Parameter Period Aux
79. e 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 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 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 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 If the trailing edge of the SYNC signal occurs after the leading edge of the first pulse but be fore the second pulse in the pulse burs
80. e desired value is too far away to reach conveniently by incrementing or decrementing the original value with the UP DOWN arrow keys One Using the Controls 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 fi EAE 10 000 040 45 mz Input A 8E 148 i x fete Trig Filter I AC 502 1x Man 0U Off Fig 2 9 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
81. e 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 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 CNT 90 and 50 ps for the CNT 91 R 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
82. easurement Functions Phase A Rel B B Rel A Range Resolution Input Frequency Min Pulse Width m Display Main Parameter Aux Parameters 180 to 360 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 Up to 160 MHz 1 6 ns Phase Freq prim channel VANNB in dB Duty Factor A B Range Input Frequency Min Pulse Width Modes m Display Main Parameter Aux Parameters 0 000001 to 0 999999 0 1 Hz 200 MHz 2 5 ns Pos or neg duty factor Duty factor Period pulse width Specifications Vmax Vmin Vp p A B Alternative data within parentheses refer to in put attenuator setting x10 Range Input Frequency Mode Resolution Accuracy typ DC 1 Hz 1 kHz 1 kHz 20 MHz 20 100 MHz 100 300 MHz 5 V to 5 V 50 V to 50 V DC 1Hz 300 MHz 100 Hz 300 MHz default higher LF limit means higher meas speed Vmax Vmin Vp p 3 30 mV 1 15 150 m 1 15 150 m 3 15 150 i 10 15 150 mV 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 Aux Parameters CNT 90 Measurement Functions Vmax or Vmin or Vp p Vmin Vp p or Vmax Vp p or Vmin Vmax Specifications Timestamping A B C This function is only accessible via GPIB or USB
83. edures or practices to prevent personal in jury Symbols Shows where the protective ground terminal is connected inside the instrument Never remove or loosen this screw This symbol is used for identifying the functional ground of an I O signal It is always connected to the instrument chassis Indicates that the operator should consult the manual 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 Fig 1 1 Do not overlook the safety in structions nform your Pendulum representative For example the instrument is likely to be un safe if it is visibly damaged Disposal of Hazardous Materials m CNT 90 amp CNT 90XL only If your instrument was ordered with a built in battery supply Option 23 90 it contains 12 Li Ion cells arranged as a fixed battery pack with internal protection circuitry Even though this type of cell does not cause environmental damage in the same way as NiCd for instance you should dispose of a worn out battery pack at an authorized recy cling station or retu
84. ell 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 is 500 s the maximum measuring time for each sample is 1000 s and the maximum number of samples is 2 10 which in effect means that a single data capture could theoretically span up to 3 10 s or more than 95000 years 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 k 1 for a confidence level of 68 3 Process 16 lim
85. en 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 15 This timing error is taken care of by using hysteresis compensa 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 toA 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 between arbitrary trigger levels Measuring Functions CNT 91 R Time Interval Error TIE This function can be found under the function menu Time and is only applicable to clock signals not data signals TIE measurement uses continuous time stamping to observe slow phase shifts wander in nominally stable
86. end plot auto scaled Sample Size 2 to 210 Max Sample Rate 250 kSa s measured 2 kSa s calculated depending on meas func tion and graphics Limit Qualifier Off Capture amp store values above limit 2 Capture amp store values below limit 1 Capture amp store values in side limits 1 and 2 Capture amp store values outside limits 1 and 2 Meas Pacing Time Range 2 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 20 ns 1000 s for Smart Period AVG amp Smart Fre quency 20 ns 2 s for PRF Freq in Burst nor mal Period AVG amp normal Frequency 4 ns 500 s for Freq back to back Single cycle for other meas functions Times gt 2 s are software controlled w reduced res olution and accuracy Measuring Time Timebase Reference Internal external or auto matic Display Hold 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 Digit Blanking Specifications 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 li
87. eps with the UP DOWN arrow keys Press Output Mode to enter the mode selection menu below Gate Open indicates to external equip ment when a measurement is in progress Pulse Generator activates a continuous pulse train having the parameters en tered in the previous menu Using the Controls Alarm can be set to be active low or ac tive high The MATH LIM menu is used Frequency fi WEAR 9 999 999 3998m User options Output 0utput Mode Gate Puls Alarm Alarm Open Gen High Low Fig 2 43 Mode selection menu for setting up the behavior and the nu merical limits that trigger the alarm The amplitude is fixed at TTL levels into 50 Q irrespective of the output mode About Here you can find information on model serial number instrument firmware version timebase option amp calibration date The CNT 91R reports Rubidium in this field RFinputoption The CNT 90XL reports the upper frequency limit m Hold Run This key serves the purpose of 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 wil
88. eq Freq A B Press INPUT B and select DC and 50 Q Press EXIT OK Perform the settings and check the Vmax and Vmin values for Input B according to Table 7 5 Reference Oscillators not CNT 91R 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 accordingly 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 Rubidium Oscillator CNT 91R m Acceptance Test Recall the DEFAULT settings Connect the reference to Input A Check the readout against the accuracy re quirements of your application To fully test the a
89. er 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 360 FREQ See the following table Measuring Functions 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 10 mV A sine wave expressed as V t 2 Vp x sin 27t has a slew rate of f Vp x 2nfclose to the zero crosssing That gives us the systematic time error when crossing 10 mV instead of crossing 0 mV 10mV Vp x 2n x FREQ 6 And the corresponding phase error in degrees is Trigger level timing error 160 MHz 28 8 The trigger level timing error is depending 499 MHz 18 0 on two factors 10 MHz 1 8 The actual trigger point is not exactly zero due to trigger level DAC uncer 1 MHz 0 18 tainty and comparator offset error 100 kHz 0 018 The two signals have different slew rates 40 kHz andbalow 0 0025 at the zero crossing Every counter has input hysteresis This is Table 4 2 Phase difference caused by necessary to prevent noise to cause errone ous input triggering The width of the hyster esis band determines the maximum sensitiv ity of t
90. eration and charg ing is not going on 2 6 Description of Keys The charging level indicator shows e the relative charging level in percent Select Function This hard key is marked MEAS FUNC When you depress it one of the menus below will open Frequency fi mun 9 999 999 959g Measure function Period Pulse Time Phase Volt Fig 2 1 CNT 90 Select measurement function Frequency fi HOLD 9 999 996 BB mz Measure function Period Pulse Power amp Time Phase Volt Fig 2 2 CNT 90XL Select measurement function Frequency fi noD 9 999 999 986 mz Measure function Period Pulse Totalize Freq Time Volt Fig 2 3 CNT 91 R Select measurement function 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 nel you will most probably get a mea
91. esented 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 Trend Plot Frequency fi 5 000 000 001 0 MHz 100 4 999 999 999 0 MHz 0 05 Ms Fig 2 8 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 or the USB bus the operating mode changes to Remote indicated by the label REM on the display All front panel keys ex cept CANCEL are then disabled See also page 2 7 for more information on this key 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 th
92. essing this softkey you get to the submenu Power Press Power and then select dBm or W as the unit of measurement when either of the functions Frequency C or Power C is selected from the MEAS FUNC menu The CNT 90 with Option 23 90 has a single submenu called Use Battery in Standby By toggling this softkey you can decide if the in ternal OCXO will remain powered or not when you turn off the instrument in battery operation mode The CNT 90XL with Option 23 90 has a com bination of the two submenus mentioned above See the figure below Frequency A nam 249 878 015 573 mz User options Misc Use Battery in Stand By No Fig 2 41 The Misc submenu for CNT 90XL with battery option 490 MEAS REM Output CNT 91 R only The rear panel pulse output can be used for three different purposes pulse generator gate indicator alarm Press the softkey Output to open the submenu below Frequency fi HEAR 10 000 000 000 mz User options Output Output Mode Off Fig 2 42 Pulse Period Pulse Width 100 ns 50 ns Selecting output mode and pulse parameters Off is the default mode and inhibits all activity on the output connector The pulse generator parameters Period and Width can be entered by first pressing the corre sponding softkeys then setting the numerical values as usual By placing the cursor over the parameter you can also set the values directly in 1 2 5 st
93. f 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 Fig 5 15 Using both start and stop arm ing to 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
94. f 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 2 8 Description of Keys 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 Numerical Frequency A MEAN MEAS 10 000 041 617 9 we 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 Fig 2 6 Statistics presented numerically In this mode the statistical information is dis played as numerical data containing the fol lowing elements Mean mean value Max maximum value Min minimum value P P peak to peak deviation Adev Allan deviation Std Standard deviation Histogram Frequency fi T MEAS 100 mHz div 10 000 041 2 MHz 0x Fig 2 7 Statistics pr
95. g factor 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 f nxd g Theory of Measurement 4 11 Measuring Functions Prescalers do not reduce resolution in recipro cal counters The relative quantization error is 100 ps still 2 be 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 12 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 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 13 Mea suring the frequency of the same signal will take twice as long since this function involves prescaling by a factor two Fig 4 13 Meas
96. g 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 has 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 grammer s Handbook 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 limi
97. gative Meas Inputs A B C option Impedance 1 MQ 50 pF or 50 Q VSWR 2 1 Connectors BNC SMA for Input C 8 8 CNT 90 Auxiliary Functions 27 dBm PIN diode prot Auxiliary Functions Trigger Hold Off Time Delay Range 20 ns 2 s 10 ns resol External Start Stop Arming Modes Start arming stop arming start and stop arming Input Channels A B E EXT ARM Max Rep Rate for Arming Signal Channel A B 160 MHz Channel E 80 MHz Start Time Delay Range 10 ns 2 s 10 ns resol NOTE Stop arming has no delay setting Statistics Functions Maximum minimum mean Dmax min standard deviation Allan deviation Display Numeric or numeric graphic Graphic Histogram amp trend plot auto scaled Sample Size 2 to 2 x 10 Max Sample Rate 250 kSa s measured 2 kSa s calculated depending on meas func tion and graphics Limit Qualifier Meas Pacing Off Capture amp store values above limit 2 Capture amp store values below limit 1 Capture amp store values in side limits 1 and 2 Capture amp store values outside limits 1 and 2 Time Range 2 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 Display Hold Digit Blanking
98. gger Level Timing Error Eti Time Interval Rise Fall Time Pulse Width Duty Factor Phase attenuator setting x1 Ey AULU 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 Specifications Hyst 6 mV 1 of trig lvl DC tol kHz for other measurement functions Example for phase with sinewave signals and 0 V trigger levels attenuator setting x1 Eu 0 001 Vpk A 0 001 Vpk g f where Vpk A Inp A peak voltage in V and Vpk B Inp B peak voltage in V m Timebase Error TBE TBE is the relative error of the timebase oscil lator dimensionless and depends on the ac tual oscillator used See Timebase Options on page 8 46 Total Uncertainty 20 The general formula for all measurement functions is Ui 2 i rand uncert Y syst uncert y Time Interval Pulse Width Rise Fall Time m Random Uncertainty rms U dm Trig Error Stop Trig Error rnd q s m Systematic Uncertainty Uus J Mex Er 500 psy TBE TIME where Eq trigger level timing error 500 ps maximum channel difference TBE timebase error TIME measurement result CNT 91 R Measurement Uncertainties 8 41 Specifications Frequency amp Period m Random Uncertai
99. gger 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 Vmin 0 2 V max Vmin Trig Level B Vmin 0 8 V max Vmin Fall Time Trig Level A V min 0 8 V max Vmin Trig Level B V min 0 2 V max Vmin 2 Select one of the dedicated Rise Fall Time functions and exploit the possibility to man 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 4 18 Pulse Width A B See the paragraph on Auto Trigger page 4 20 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 t
100. ggering 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 mer s Handbook 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 sin gle shot phenomena which are either trig gered manually or occur at long intervals An other reason for using this
101. ggering 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 signal 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 do not attenuate the signal too much and set the sensitivity of the counter high Input Signal Conditioning In practice however trigger errors caused by erroneous counts Fig
102. gt 3 9 M readings w calibr off ASCII IEEE double preci sion floating point USB Interface Version Protocol 8 40 CNT 91 R Auxiliary Functions 2 0 Full Speed 12 Mb s 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 Up to 100 Msa s equiv sample rate 10 ns be tween samples Continuous Single Period Yes from LF to 250 kHz repetition rate Waveform Capture Yes Data Analysis Features 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 Measurement Uncertainties Random Uncertainties 1c m Quantization Error Eq Eq 65 ps rms lt 50 ps rms typical m Start Stop Trigger Error Ess 2 2 Ess Ese Eae 8 l y L2 AE noise input noise signal y s inp sign slew rate P at trig point noise Ej Single Period Jitter rms s Vnoise input 500 uVrms internal noise 200 uVrms typical The rms noise of the applied signal Vnoise signal Systematic Uncertainties m Tri
103. hapter 5 2 Measurement Time 5 2 Gate Indicator c toe 5 2 Single Measurements 5 2 Hold Run amp Restart 5 2 AMINO ERN REPRE 5 2 Start Arming 2 5 5 3 Stop Armitig x a erp one 5 3 Controlling Measurement Timing 5 4 The Measurement Process 5 4 Resolution as Function of Measurement Time 5 4 Measurement Time and Rates 5 5 What is Arming 5 5 Arming Setup Time 5 9 Arming Examples 5 9 Introduction to Arming Examples 5 9 1 Measuring the First Burst Pulse 5 9 2 Measuring the Second Burst US ie a sisate voce donen erei E bere tabi 5 11 3 Measuring the Time Between Burst Pulse 1 and 4 12 4 Profiling 0 5 13 6 Process Introd ctioni uos cc eee 6 2 Averaging 00 00 eae 6 2 Mathematics 4006s ceed cea wae eee 6 2 Example ase eere grs 6 2 Statistics soos Lo ee t dtd a aed 6 3 Allan Deviation vs Standard Deviation 6 3 Selecting Sampling Parameters 6 3 Measuring Speed 6 4 Determining Long or Short Time Instability llle 6 4 Statistics and Mathematics 6 5 Confidence Limits 6 5 Jitter Measurements 6 5 NETTIE cache neh ie ene ul osea dup scd 6 6 Limit Behavior 6 6 Limit Mode losen ea as 6 7 Limits and Graphi
104. he counter It is approximately 30 mV so when you set a trigger level of 0 V the ac tual trigger point would normally be 15 mV and the recovery point 15 mV This kind of timing error is cancelled out by using hyster esis 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 inter channel propagation delay difference 10mV x 360 x FREQ Vp x 2n x FREQ which can be reduced to B This error can occur on both inputs so the worst case systematic error is thus 0 6 0 6 Ve 4 Vp B C Possible Errors 4 23 Measuring Functions Now the current measurement result Xo will be subtracted from the future phase measurements made by selecting Phase A rel B A considerable part of the systematic phase errors will thus be cancelled out Note that this calibration has to be repeated if the E Vpeak Vpeak Worst case A B systematic error 150 mV 1150mV 4 4 8 1 5V 150 mV 0 4 4 4 4 1 5V 1 5V 0 4 0 4 0 8 Table 4 3 error examples 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
105. he section deal ing with these matters at the end of this chap ter Coupling Switch between AC coupling and DC cou pling by toggling the softkey AC DC DC Coupling AAAA Ac Coupling AAA 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 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 Input Signal Conditioning missed while Fig 3 5shows that triggering does not occur at all because the signal ampli tude and the hysteresis band are not centered NOTE For explanation of the hysteresis band see page 4 3 LL Fig 3 5 No triggering due to AC coupling of signal with low duty cycle Filter If you cannot obtain a stable reading the sig nal to noise
106. he start trigger slope The counter automatically selects the inverse polarity as stop slope Duty Factor 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 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 Pulse width Duty factor yf Period The total measurement time will be doubled compared to a single measurement because Duty requires 2 measurement steps Measurement Errors Hysteresis The trigger hysteresis among other things causes measuring errors see Figure 4 18 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 Fig 4 18 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 Measuring Functions Overdrive a
107. hem are handled by measures taken by the in strument firmware Two examples Theory of Measurement 4 13 Measuring Functions One of the step frequencies produces an IF but not its shifted value Action go to the next table value Frequency modulation causes an unstable n value calculation Action increase the measuring time Power measurement Another feature in this instrument is the abil ity to measure power with high resolution and moderate accuracy over the entire frequency range achieved by storing individual fre quency dependent power correction factors in a memory located inside the conversion unit This memory is also used for storing other in formation about the converter like identifica tion data PERIOD Single A B amp Avg A B C From a measuring point of view the period function is identical to the frequency function This is because the period of a cyclic signal has the reciprocal value of the frequency 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 4 14 PERIOD All other functions and features as described earlier under Frequency apply to Period measurements as well Single A B Back to Back m CNT 91 R only This function benef
108. 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 Frequency A Meas 90 000 001 77 mz Input A Filter Digital LP Freq ETT kHz Hz MHz 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 3rd or 4th cycle A cutoff frequency that is too 3 4 Input Amplifier 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 Correct measurement Fig 3 8 Digital LP filter operates in the measuring logic not in the input amplifier Man Auto Toggle bet
109. ier 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 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 Vo
110. igger indicator according to Table 7 4 Press the Trig key and enter 1 V via the keyboard by pressing the X 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 Freq 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 Fail 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 MO 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 first Vmax and Vmin voltage lev els on the display according to 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 Fr
111. ime 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 displayed 1 KeX L 2 KIX L 3 K X L M 4 KIX L M 5 XIM 1 Press MATH LIM Math to enter the first mathematics submenu See page 2 13 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 le
112. ime 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 new 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 qualif
113. imit 1 Capture amp store values in side limits 1 and 2 Capture amp store values outside limits 1 and 2 Time Range 2 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 Display Hold Digit Blanking 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 gt 2 s are software controlled w reduced res olution and accuracy Internal external or auto matic 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 Limit Alarm Limit Values Settings On Alarm Display Numeric Graphic Stored Instrument Setups Display Type amp Use Resolution Technology Specifications Annunciator on display and or SRQ via GPIB Lower limit limit 1 Upper limit limit 2 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 limit 1 Stop or Continue Numeric graphic Current measurement value annunciator for limit alarm Horizontal line w up per lower limit markers current value marker 20 comp
114. 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 instrument 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 m
115. is counted Max Frequency 160 MHz Min Pulse Width 2 5 ns Timestamp Reso lution Max Frequency to catch each edge 70 ps rms 250 kHz Auto Set Manual Set All measuring functions can be auto set using best 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 400 MHz AC coupled 10 Hz 400 MHz Coupling AC or DC Rise Time Approx 700 ps Impedance 1 MO 25 pF or 50 Q VSWR 2 Trigger Slope Positive or negative Channels Separate A amp 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 300 400 MHz 35 mVrms Auto Trig 35 mVrms Attenuation x1 x10 Dynamic Range x1 30 mVp p to 10 Vp p within 5 V window 8 20 CNT 90XL Input and Output Specifications Trigger Level Resolution Uncertainty Auto Auto Hysteresis Time Meas Freq Meas amp Per Avg Freq Range Analog Noise Reduction
116. 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 Description of Keys 2 11 Using the Controls Miscellaneous Frequency A XII MEAS 248 669 081 321 mz Settings Misc Frequency A 4 35x MEAS 248 267 648 103 mz Settings Misc Input C Acq n rueda poto iris krea c leas Rf t Acquisition ES CE S Fig 2 19 CNT 90 The Misc submenu Fig 2 22 CNT 90XL The Input C Acqui Frequency fi X052 MEAS 248 337 522 698 mize Settings Misc Interp Smart Auto Trig Input C Calib Meas Timeout Low Freq fica On orn 100 Hz Auto Fig 2 20 CNT 90XL The Misc submenu Frequency fi mas 39899989899 Settings Misc ed Smart fiuto Trig II Meas Timeout Low Freq TIE On Off 100 Hz Auto Fig 2 21 CNT 91 R The Misc submenu The options in this menu are Smart Measure with submenus Smart Time Interval valid only if the selected measurement function is Time Interval The counter decides by means of timestamping which measurement channel precedes the other Smart Frequency valid only if the selected measurement function is Frequency or Period Average By means of continuous timestamping and
117. its k 7 2 for a confidence level of 95 596 26 limits k 3 for a confidence level of 99 7 3c 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 confidence limits 2sx 2 50 ns 100 ns The 36 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 means of the built in graphic capability tog Statistics
118. its from the basic time stamping calculation method utilized by this series of counters to obtain consecutive measurement results without dead time Every positive or negative zero crossing de pending on the selected slope up to the maxi mum frequency 125 kHz with interpolator calibration ON or 250 kHz with interpolator calibration OFF is time stamped For every new time stamp the previous value is sub tracted from the current value and displayed In VALUES mode the display is updated ev ery new period if the period time exceeds 200 ms For shorter times every second third etc result is displayed due to the limited up dating rate In STATISTICS mode the graphs and statisti cal data contain all periods up to the maxi mum input frequency see above For higher frequencies the average period time during the 4 or 8 us observation time is displayed So for higher frequencies the actual function is rather Period Average Back to Back The main purpose of this function is to make continuous measurements of relatively long period times without losing single periods due to result processing A typical example is the 1 pps timebase output from GPS receivers Measuring Functions Frequency A B Back to Back Wm CNT 91 R only This is the inverse function of Period Back to Back In STATISTICS mode mea surement time is used for pacing the time stamps The pacing parameter is not used in this case Thus a series of consecut
119. ive frequency aver age measurements without dead time can be made in order to fulfil the requirements for correct calculation of Allan variance or devia tion These statististical measures are for in stance widely used by oscillator manufactur ers to describe short term stability PERIOD 4 15 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 Fig 4 15 Time is measured be tween the trigger point and the reset point Accurate measurements are possible only if the hysteresis band is narrow 4 16 Introduction 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 normally 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 Ev
120. k the normal way An Auto Once is performed instead before the start of a measurement in order to calculate suitable trigger levels once TOT A MAN This mode enables you to totalize count the number of trigger events on Channel A Aux iliary calculated parameters are A B and A B Start Stop is manually controlled by toggling the key HOLD RUN and the counting regis ters are reset by pressing RESTART TOT B MAN This mode enables you to totalize count the number of trigger events on Channel B Aux iliary calculated parameters are A B and A B Start Stop is manually controlled by toggling the key HOLD RUN and the counting regis ters are reset by pressing RESTART TOT A B MAN This mode enables you to calculate the sum of trigger events on Channel A and Channel B Auxiliary parameters are A and B Start Stop is manually controlled by toggling the key Totalize in General 4 25 Measuring Functions HOLD RUN and the counting registers are reset by pressing RESTART TOT A B MAN This mode enables you to calculate the differ ence between trigger events on Channel A and Channel B Auxiliary parameters are A and B Start Stop is manually controlled by toggling the key HOLD RUN and the counting regis ters are reset by pressing RESTART Applications The TOT A B MAN makes it possible for instance to make differential flow measure ments in control systems Example the number of cars in a parking lot equals
121. 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 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 manage 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 b
122. l not affect any front panel settings Description of Keys 2 17 Using the Controls Default Settings See page 2 15 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 Time 20 ms Trigger Level AUTO Mathematics Trigger Slope POS Mathematics OFF Impedance 1 MQ Math Constants K 1 L 0 M 1 Attenuator 1x Limits Coupling AC Limit State OFF Filter OFF Limit Mode RANGE Arming Lower Limit 0 Start OFF Upper Limit 0 Start Slope POS Burst Start Arm Delay 0 Sync Delay 400 us Stop OFF Start Delay 0 Stop Slope POS Meas Time 200 us Hold Off Freq Limit 400 MHz Hold Off State OFF Miscellaneous Hold Off Time 200 us Function FREQA Time Out Smart Frequency AUTO Time Out State OFF Smart Time Interval OFF Time Out Time 100 ms Meas Time 200 ms Statistics Auto Trig Low Freq 100 Hz Statistics OFF Timebase Reference AUTO No of Samples 100 Blank Digits 0 No of Bins 20 Pacing State OFF 2 18 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 unde
123. le Shot Input Frequency Min Pulse Width Smart Calculation m Display Main Parameter Aux Parameters 0 ns to 108 S 10 to 108 s 100 ps Up to 160 MHz 1 6 ns 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 Time interval None Pulse Width A B Range Input Frequency Modes m Display Main Parameter Aux Parameters 2 5 ns 1089s Up to 200 MHz Pos pulse width or neg pulse width Pulse width Vmax Vmin Vp p Rise and Fall Time A B Range 8 18 CNT 90XL Measurement Functions 1 5 ns 1000 s Input Frequency Up to 160 MHz square wave Trigger Levels Default 10 and 90 Manually adjustable Min Pulse Width 1 6 ns Modes Rise or fall time Min Amplitude 100 mVp p m Display Main Parameter Rise or fall time Aux Parameters Slew rate Vmax Vmin 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 Input Frequency 0 1 Hz 200 MHz Min Pulse Width 2 5 ns Modes Pos or neg duty factor CNT 90XL Specifications m Display Main Parameter Du
124. lete setups can be saved and recalled from internal non volatile memory 10 can be user protected Graphics screen for menu control numerical readout 14 digits and status info 320 x 97 pixels Monochrome LCD with white LED backlight GPIB Interface Programmable Functions Compatibility Modes All front panel accessible functions IEEE 488 2 1987 SCPI 1999 Native mode Agilent compatible mode CNT 90XL Auxiliary Functions 8 23 Specifications Agilent Compatibility Interface Func tions Max Meas Rate Via GPIB To Internal Memory Internal Memory Size Data Output HP 53131 132 181 com mands are emulated Code and response for mat is compatible No tim ing compatibility No reso lution compatibility SH1 AH1 T6 L4 SR1 RL1 DC1 DT1 E2 2000 readings s block 350 readings s individual 250 k readings s Up to 750 k readings ASCII IEEE double preci sion floating point USB Interface Version Protocol TimeView 2 0 12 Mb s USBTMC USB488 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 Repetitive Sampling 250 k readings s Up to 100 Msa s equiv sample rate 10 ns be tween samples 8 24 CNT 90XL Battery Unit Continuo
125. lso 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 pressing OK N f CNT 90 TIMER COUNTER ANALYZER 100ps 300M iz pendulum A Be qub Ug Q eo Ns We erg y c5 9 12Vrms SF UTA INPUT E O SETTINGS MAA TN USER OP HOLD RUN RESP d NC 30Vrms M e TRIGGER IN GATE INDI DICATORS CATOR Blinking LED in pending mea dicates correct indi triggering causes the NUMERIC INPUT KEYS Sometimes you may want to enter numeric values like the LED to light up RF MICROWAVE MAIN INPUTS INPUT CNT 90 91 R The two identical DC A number of op coupled channels A amp tional RF B are used for all prescalers are types of measure ilabl ments either one ata ee time or both together CNT 90XL One of a number of microwave convert ers is mounted 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 Conn type dep on frequency spec Rear Panel Type Plate I
126. lt 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 Stop Delay can only be used for realizing the function Timed Totalize in the CNT 91 R 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 the input signal meets the stop trigger conditions That hap pens directly after the following events 5 4 The Measurement P
127. manual arming could simply be to allow sufficient time to write down individual results m When Do I Use Start Arming Sync I M Pulse Signal WU UU 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 Do 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 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 perfo
128. 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 calibration 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 ms 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 ofa controller e g a PC although it is possible but tedious to manuall
129. ments 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 harmonic 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 coop 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 bee
130. mit 2 Alarm if value gt limit 2 or value 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 recalled from internal non volatile memory 10 can be user protected In statistics mode w HOLD activated 8 datasets w max 32000 samples can be saved and recalled from internal non volatile memory Stored Datasets 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 CNT 91 R Auxiliary Functions 8 39 Specifications Compatibility Modes Agilent Compatibility Interface Func tions Max Meas Rate Via GPIB To Internal Memory Internal Memory Size Data Output IEEE 488 2 1987 SCPI 1999 Native mode Agilent compatible mode HP 53131 132 181 com mands are emulated Code and response for mat is compatible No tim ing compatibility No reso lution compatibility SH1 AH1 T6 L4 SR1 RL1 DC1 DT1 E2 13 9 k readings s block 650 readings s individual 4 k readings s talk only 250 k readings s 100 k readings s w calibr on
131. n 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 VMN Vpr 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 CNT 90 TIMER COUNTER ANALYZER 100ps 300MHz pendulum teet Measuring Functions Frequency Measurements FREQ A B The counter measures frequency between 0 Hz and 400 MHz on Input A and Input B Frequencies above 100 Hz are best measured using the Default Setup See page 2 15 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
132. n 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 Measuring Functions If the counter triggers on noise widen the Even though the main frequency reading may hysteresis band with the variable hyster now be unstable the PRF value on the display esis function i e enter a trigger level will represent the modulating frequency gt 0 V but lt Vp pmin See Fig 4 8 Modulating 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 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 2 Press INPUT A and turn
133. nally left blank Chapter 10 Service Sales and Service Office For additional product information customer support and service please contact Spectracom at the following addresses Spectracom Orolia Global Services AB Box 20020 SE 161 02 Bromma Sweden Office Address Karlsbodavagen 39 Bromma Stockholm Sweden Shipping Address Karlsbodavagen 39 SE 168 67 Bromma Sweden Phone 46 0 8 5985 1000 Fax 46 0 8 5985 1040 E mail service pendulum se Internet www spectracomcorp com Spectracom Corporation 5811 Racine Street Oakland CA 94609 USA Office Address As above Shipping Address As above Phone 1 510 428 9488 Fax 1 510 428 9469 E mail techsupport spectracomcorp com Internet www spectracomcorp com Chapter 11 Appendix New Look A new front panel design will be introduced gradually starting with the model CNT 91R It will eventually be applied to all models in the OX series of counters The fundamental layout is unchanged so the instructions given in the main manual are still valid The new look can be seen below CNT 91R frequency calibrator analyzer pendulum eee eo Da 0 6 e o oo0o00 7 A inputA inputB settings math lim useropt hold run restart The CNT 91R front panel 11 2 New Look
134. nd 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 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 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 Measurement Errors 4 19 Measuring Functions 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 T
135. ndicates instrument type and serial number Pulse Output CNT 91 R only User definable to serve as output for built in pulse gener ator gate indicator or alarm Optional Main Input Connectors not with Option 23 90 The front panel inputs can be moved to the rear panel by means of an optional cable kit Note that the input capacitance will be higher Fan A temp sensor controls the speed of the fan Normal bench top use means low speed whereas rack mount ing and or options may result in higher speed Using the Controls Protective Ground Terminal This is where the pro tective ground wire is connected inside the in strument Never tamper with this screw Line Power Inlet AC 90 265 VRMS 45 440 Hz no range switching needed Ie PULSE OUT TIL LEVELS IN 500 INPUT A INPUTB e INPUTC NS Reference Output 10 MHz derived from the internal or if present the external reference External Reference Input Can be automatically se lected if a signal is pres ent and approved as timebase source see Chapter 9 External Arming Input See page 5 7 GPIB Connector Address set via User Op tions Menu USB Connector Universal Serial Bus USB for data commu nication with PC Ext DC Connector Part of Option 23 90 for CNT 90 XL Range 12 18 V
136. nge 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 15 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 STANDBY INPUT A Input A for setting Slope Coupling Impedance etc Man Trig Trig xy mV Menu for entering numeric values in V or mV 0 123V Trig 0 123 V lt 5 times Trig V 4 567 Trig 4 567 V lt 5 times Trig V 8 9 Trig 8 9 V Trig 8 9 V mV Trig 8 9 mV V Trig 8 9 V AUTOSET Menu disappears INPUT B Input B A for setting Slope 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 HO
137. nitor 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 PHP E x ES SS 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 intentionally 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
138. nterval 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 1 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 m A Using Trigger Hold Off to Delay the Stop a Certain Time Trigger Hold Off is used to inhibit stop trig gering during a preset 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 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 Of
139. nty rms Smart Mode For measuring times 200 ms and if Smart Freq AUTO or OFF fe 2 Start Trigger oor U x rnd Measuring Time x Measurement Result Hz or s For measuring times gt 200 ms and if Smart Freq AUTO or ON 2s EA 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 amp N Measuring Time 8 us Normal Mode fe 2 Start Trigger Error rnd i Measuring Time x Measurement Result Hz or s m Systematic Uncertainty Both Modes Uy he TBE MR 200 ps MT MR Hz or s where MR Meas Result Freq or Per MT Meas Time Frequency Ratio f f W Typical Random Uncertainty rms NOTE Frequency Ratio is an auxiliary mea surement function intended to give an indica tion with no guaranteed specification U ma 2 x presc fact x fi x JEz Essyiy Esm dimensionless e g ppm Prescaling Factor Input 2 A amp B 16 C 3 GHz 256 C 8 GHz 128 C 15 amp 20 GHz W Typical Systematic Uncertainty rms Us TBE xTz where T is Phase m Typical Random Uncertainty rms NOTE Phase is an auxiliary measurement function intended to give an indication with no guaranteed specification Umi ze Strt Trg Err Stop Trg Er x xFreq
140. oDooo z G CO CO CO G2 CO COD MAXA INPUT A INPUT B SETTINGS MAH Li USER OPT nc RUN RESTART 12Vrme D 30Vrms XM S STANDBY LED 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 or to the rubidium oscillator in the CNT 91R 2 2 Basic Controls STANDBY ON Toggling secondary power switch Pressing this button in standby mode turns the counter ON and restores the settings as they were at power down MATH LIMIT 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 record ing USER OPT Controls the follow ing items 1 Settings memory 2 Calibration 3 Interface 4 Self test 5 Blank digits 6 About STAT PLOT Enters one of three statistics presentation modes Switching be tween the modes is done by toggling the key VALUE Enters the nor mal numerical presentation mode with one main parameter and a number of auxiliary parame ters MEAS FUNC Menu tree for selecting mea surement func tion You can use the seven softkeys below the dis play for confir mation Using the Controls AUTO SET Adjusts inpu
141. oltage levels Vmax VMIN and Vpp on DC input voltages and on repeti tive signals between 1 Hz and 400 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 Fig 4 21 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 The voltage is determined by making a series of trigger level settings and sensing when the counter triggers Vmax VMiN VPP 4 29 Measuring Functions 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 Vims 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 input 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 amp Math Off amp K X
142. on Manual trig ger Press Trig and enter a trigger level that makes the counter trigger according to Fig 4 9 AM Signals 4 9 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 counting 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 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 4 10 Theory of Measurement 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 m g The 9X measures the gate time tg with a
143. ons 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 this menu NOTE Stop Delay can only be used for realiz ing the function Timed Totalize in the CNT 91 R Trigger Hold Off Frequency A M00 MEAS 200 139 457 252 mz Settings TriggerHold Off Trigger Hold Off Hold Off Off 200 us Fig 2 16 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 Using the Controls start A typical use is to clean up signals gen erated by bouncing relay contacts Statistics Frequency in Burst fi MEAS 4 134 663 8 mz Settings Stat No Of Ho Of Pacing Samples Bins Pacing Time 100 20 Off is Fig 2 17 Entering statistics parameters In this menu you can do the following Setthe number of samples used for cal culation of various statistical measures Setthe number of bins in the histogram view Pacing The delay between measurements called pacing can be set to ON or OFF and the time can be set within the range 2 us 500 s Timebase Reference Frequency fi neas 4 194 664 464 mz Settings TimebaseRef Int Ext futo Fig 2 18 Selecting timebase reference source Here you can decide if the counter
144. op trigger errors that should be added For sinusoidal input signals each error is 360 2n x5 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 2nx100 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 above Random error 4 quant err start trg err stop trg err The total random errors are thus 40 04 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 7 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 Systematic errors consist of 3 elements Inter channel propagation delay difference Trigg
145. or 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 Hz 400 MHz Input B 0 002 Hz 400 MHz Input C 100 MHz 3 GHz Opt 10 300 MHz 8 GHz Opt 13 200 MHz 15 GHz Opt 14 200 MHz 20 GHz Opt 14B Resolution 12 digits s m Display Main Parameter Frequency Aux Parameter A B Vmax Vmin Vp p Specifications 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 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 2 5 ns 500s Input C 3 GHz 330 ps 10 ns 8 GHz 125 ps 3 3 ns 15 GHz 72 ps 5 ns 20 GHz 50 ps 5 ns
146. ount kit consists of the following 2 brackets short left long right 4 screws M5 x 8 4 screws M6 x 8 Fig 1 2 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 Assembling the Rackmount Kit Make sure the power cord is disconnected from the instrument Turn the instrument upside down See Fig 1 4 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 108 j i E af lt lt Fig 1 4 Remove the screws and push the counter out of the cover 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 Fig 1 6 Removing feet from the cover Push the inst
147. r 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 Performance Check Duration approx 50 ns Rise time 2 ns Restore the timer counter s default 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 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 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 Rear Inputs Outputs 7 9 Performance Check 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 abo
148. 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 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 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
149. regression analy sis the resolution is increased for measuring times between 0 2 s and 100 s Input C Acquisition CNT 90XL only Auto means that the whole specified fre quency range is scanned for valid input signals 2 12 Description of Keys sition submenu Manual means that a narrow band around the manually entered center fre quency is monitored for valid input sig nals This mode is compulsory when measuring burst signals but is also rec ommended for FM signals when the ap proximate frequency is known An additional feature is that the measure ment results are presented much faster as the acquisition process is skipped NOTE Signal frequencies outside the manual capture range may cause erroneous results In order to draw the operator s attention to this eventuality the sign M ACQ is visible in the upper right corner of the display 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 consequently 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 Interpolatator Calibration By switching off the interpolator calibra tion you can increase
150. rement Process 5 7 Measurement Control STOP yes WAIT FOR Fig 5 5 Measurement control flow diagram 5 8 The Measurement Process Arming Setup Time The arming logic needs a setup time of about 5 nanoseconds before the counter is really armed see Fig 5 6 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 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 Measurement Control Arming Examples Introduction to Arming Examples The following arming examples are available 1 Measuring the first pulse in a burst 2 Measuring the second 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
151. riations versus the reference tempera ture The operating tem perature range and the calibration interval are part of this specification Specifications 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 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 CNT 90 General Specifications 8 13 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 CNT 90 400 MHz 100 ps Included with In strument RF Input Options Option 10 Option
152. rig Low Freq You can reach it by pressing SETTINGS Misc 4 20 Measurement Errors Measuring Functions Phase What is Phase Phase is the time difference between two sig nals of the same frequency expressed as an angle channel B are enough to calculate the result including sign Resolution Phase Fig 4 19 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 calculated as 360 x Time Interval A B Period or in other words Phase A B 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 Fig 4 20 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 Possible Errors Phase can be measured on input signal fre quencies up to 160
153. rm 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 not start erroneously during the Burst Off du ration or inside the burst 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 be reliable at least two measurements must be made the first to synchronize the measure 4 6 Frequency Modulated Signals ment and the second from which the measure ment result can be read out 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
154. rmed 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 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 O 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 complex 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
155. rn it to Pendulum Note Individual cells cannot be replaced 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 Pendulum sales or service orga nization in case repair or replacement may be required Check List The shipment should contain the following Counter Timer Analyzer CNT 90 91 or Frequency Calibrator Analyzer CNT 91R or Microwave Counter Analyzer CNT 90XL Line cord N to BNC Adapter only CNT 90 91 R with prescaler options having a type N connector 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 User s Manual Programmer s Handbook Identification The type plate on the rear panel shows type number and serial number See illustration on page 2 5 Installed options are listed under the menu User Options About where you can also find information on firmware version and calibration date See page 2 14 Installation Supply Voltage W Setting The Counter may be connected to any AC supply with a voltage rating of 90 to 265 Vims 45 to 440 Hz The counter automati cally adjusts it
156. rocess 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 f is f tg 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 dis played value is 10000000 Then the quantization resolution corresponds to 0 5 LSD units 1 unit in 99999999 1E8 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 tional digit suddenly gives ten times more dis play resolution but not a ten times less quantization uncertainty Consequen
157. rstand 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 Frequency fi TEAR 10 000 040 45 mz Input A Bc ib i8x fete Trig Filter I AC 50n 1x Man ov off Fig 3 2 Input settings menu Impedance The input impedance can be set to 1 MQ or 50 Q by toggling the corresponding softkey CAUTION Switching the impedance to 50 O 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 signal ex ceeds the dynamic input voltage range 5 V or IMP CROSSPOINT MEASURING MICRO COUPL CONV FILTER SWITCH COMP LOGIC CONTROLLER IMP ATT COUPL IMP FILTER COMP CONV TRIG LVL ADj TRIG LVL Bi Fig 3 1 3 2 Input Amplifier Block diagram of the signal conditioning else when attenuation can reduce the influence of noise and interference See t
158. rument back into the cover See Fig 1 4 Mount the two rear feet with the screws B to the 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 INPUT A Opens the menu from which you can adjust all settings for Input A like Coupling Impedance and Attenuation Basic Controls A more elaborate description of the front and rear panels including the user interface with its menu system follows after this introductory 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 See also the appendix SETTINGS Select measurement pa rameters such as mea surement time number of measurements and so on f CNT 90 TIMER COUNTER ANALYZER 100ps 300MHz gt pendulum 22 GIN Y N DD QA
159. s 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 All all tests performed in sequence 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 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 cha
160. s 8 9 Specifications Agilent Compatibility Interface Func tions Max Meas Rate Via GPIB To Internal Memory Internal Memory Size Data Output HP 53131 132 181 com mands are emulated Code and response for mat is compatible No tim ing compatibility No reso lution compatibility SH1 AH1 T6 L4 SR1 RL1 DC1 DT1 E2 2000 readings s block 350 readings s individual 250 k readings s Up to 750 k readings ASCII IEEE double preci sion floating point USB Interface Version Protocol TimeView 2 0 12 Mb s USBTMC USB488 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 Repetitive Sampling 250 k readings s Up to 100 Msa s equiv sample rate 10 ns be tween samples 8 10 CNT 90 Battery Unit Continuous Single Period Waveform Capture Data Analysis Features Yes 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 Battery Unit Option 23 90 Battery Type Ext DC Input Connector Oper amp Charg Temp
161. s after Com pensation Sensitivity DC 200 MHz 200 300 MHz 300 400 MHz Auto Trig Attenuation Dynamic Range x1 DC 400 MHz 10 Hz 400 MHz AC or DC Approx 700 ps 1 MQ 25 pF or50 Q VSWR 2 1 Positive or negative Separate A amp B 500 ps Approx 30 300 mVp p 5 50 mV DC 10 kHz 15 mVrms 25 mVrms 35 mVrms 35 mVrms x1 x10 30 mVp p to 10 Vp p within x5 V window Trigger Level Resolution Uncertainty Auto Auto Hysteresis Time Meas Freq Meas amp Per Avg Freq Range Analog Noise Reduction Filter Digital LP Filter Trigger Indicators Max Voltage w o Damage 1 MO 50 O Connector Read out on display 1 10 mV 15 150 mV x 1 of trigger level Automatically set to 50 or 70 of input signal 10 and 90 for rise fall time Relative level in man ually adjustable when necessary Minimum hysteresis win dow compensation 70 and 30 of input signal Minimum hyster esis window if arming on A or B is activated gt 1 Hz default 100 Hz Nom 100 kHz RC type 1 Hz 50 MHz using trig ger hold off LED 350 V DC ACpk DC to 440 Hz falling to 12 Vas x1 and 120 VRMS x10 1 MHz 12 VRMS BNC Input C Option 10 Freq Range Prescaler Factor Operating Input Voltage Range 100 300 MHz 0 3 2 5 GHz 2 5 2 7 GHz 2 7 3 0 GHz 8 36 CNT 91 R Input and Output Specifications 1
162. s 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 low 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 tri
163. self to the input line voltage Unpacking 1 7 Preparation for Use 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 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 Battery Supply m CNT 90 amp CNT 90XL only It is possible to run the counter from an op tional battery supply Option 23 90 You must charge the battery before use or storage The counter charges the battery auto matically when connected to line power or an external DC source whether the instrument is in standby or turned on See the specifications for charging time in different modes of opera tion 1 8 Unpacking Grounding Grounding faults in the line voltage supply will make any instrument connected to it dan gerous
164. set used in this mode fully exploits all the features of this instru ment series 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 mas 4 194 669 437 mz User options Test Test mode Start all test Fig 2 39 Self test menu 2 16 Description of Keys Press Test Mode to open the menu with avail able choices Frequencu fi EAS 4 194 669 038 mz User options Test Testmode BI Ram ROM Logic Display Interface Fig 2 40 Selecting a specific test Select one of them and press Start Test to run it Digits Blank Jittery measurement results can be made easier 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 represented by dashes on the display The default value for the number of blanked digits is 0 Misc CNT 90XL amp CNT 90 with Op tion 23 90 The CNT 90XL without Option 23 90 has a single submenu called Units By pr
165. sure 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 Set automatic trigger levels Switch attenuators to 1x Turn on the display Set Auto Trig Low Freq to 100 Hz if fn 3100 Hz or to fin if 10 lt fin lt 100 Hz or to 10 Hz if fin 10 Hz A higher value means faster settling time 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 following 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 SetTimebase Ref to Auto Using the Controls 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 15 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
166. t 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 Measurement Control If the SYNC pulse timing is not so suitable as in the above measurement example then arm 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 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 and 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 Fig 5 13 Measuring a time i
167. t trigger voltages automatically to the optimum lev els for the cho sen measure ment function Double click for default settings CURSOR CONTROL The cursor position marked by text inversion on the display can be moved in four directions GE CNT 90 TIMER COUNTER ANALYZER 100ps 300M 4z t3 e t3 e ee As 2 pendulum e TRIC TRIG BE 30 MHz o MOOOOODOO CO CO CO CO CO CO COD f MAX INPUT A INPUT B SETTINGS MNH LM USER OP HOLD P RESTART 12Vrme 9 30Vrms XM gy o B S7 m 0 2 8GHz L HOLD RUN RESTART EXIT OK CANCEL ENTER Initiates one CON a EL Confirms menu Toggles between HOLD one shot mode and RUN continuous mode Freezes the result after completion of a measurement if HOLD is active new measure ment if HOLD is active selections and moves up one level in the menu tree Moves up one menu level with out confirming selections made Exits REMOTE mode if not LOCAL LOCKOUT 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 a
168. t ESI CR S re d Rn 4 15 duty factor 4 17 period ic ss tira tee apie ER 4 13 pulse width 4 17 sefa ccna cages Res Be 4 16 time interval 4 16 time interval error TIE 4 16 to setup arming 5 9 TIMEOUT euere es bhewaw ae ook 2 12 4 10 range iae caes anuid aae gnuo i 4 10 Total Reset 00 2 15 Totallze oer permet 4 24 AManual 4 24 AIB Manual 4 25 A B Manual 4 24 A B Manual 4 25 BManual 4 24 Caled tsi cin giclee tensa RAO 4 26 ingeneral 008 4 24 Star SIOp oe een 4 25 Titled iee fairi zr RR bs 4 26 Totalize amp Arming 4 25 Touch hold See Sample hold Transient profiling 5 14 Trigger eor see eee mes 3 8 Trigger Hold Off 3 4 Trigger hysteresis 3 6 Trigger indicators checking 7 7 Trigger level QUO x iut outs eset he Ves 3 4 converting auto to manual 3 5 howtouse occa cor rs 3 7 manual RR 3 4 setting speed 3 4 U UNIS erp nre Sues 2 16 V VCO step response profiling 5 14 Voltage 2 2 0 002 ee eee 4 28 checking 7 6 7 8 TUNCHOMN ok Re d Rr 4 28 X X MAR seu ae eek pini ie pie nE wee 6 3 CMM obi fined panties Rupe ghar Gees 6 3 P doro 6 3 T X Index This page is intentio
169. t 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 limits 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 A En MEAS Frequency fi du dA 10 000 044 MHz 100 43 333 999 B mz ub uL 9 49 900 000 000MHz 50 100 000 000MHz Umax 1 490 U Unin 2 529 U Up p 4 019 U Fig 6 3 The analog limit mo
170. t panel push button HOLD RUN Statistics and pac ing inhibited CNT 91 R Measurement Functions Specifications GATED START STOP and TIMED controlled by setting arming conditions on the free input channels Statistics and pacing allowed Timestamping A B 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 Max Frequency to catch each edge 50 ps rms 250 kHz Auto Set Manual Set All measuring functions can be auto set using best settings for the individual functions This means e g an auto hysteresis of 33 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 8 35 Specifications Input and Output Specifications Inputs A and B Alternative data within parentheses refer to in put attenuator setting x10 Frequency Range DC coupled AC coupled Coupling Rise Time Impedance Trigger Slope Channels Max Channel Timing Difference Hysteresis Window Residual Hyster esi
171. t the counter find the optimum trigger conditions on its own Press MATH LIM Math L If 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 0 EE 6 Confirm by pressing EXIT OK Now the constant L is updated and displayed as 10E6 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 xi values MEAN Displays the arithmetic mean value
172. ted Crystal Oscillator OCXO Oven Controlled Crystal Oscillator 8 46 CNT 91 R Timebase Options CNT 91 Specifications Timebase Specifications CNT 91R Product Family 9X Timebase Type Rubidium Uncertainty due to Calibration adjustment tolerance 12 23 C 3 C lt 6x10 Aging per 24h n a per month Desy101 per year 2 2x10 10 Temperature variation 0 C 45 C lt 1x10 1 20 C 26 C typ values 1 2x10 Power voltage variation 10 tto Short term stability Root Allan Variance t4s bo 12 Typical values t 10s 3x10 Power on stability Deviation versus final value after 24 h on time after a warm up time 40 of 12 min 5x10 Time to lock 225 C appr 5 min Total uncertainty for operat ing temperature 0 C to 45 C 2c 95 confidence interval 40 1 year after calibration ay ag 2 years after calibration lt 5x10 Typical total uncertainty for operating temperature 20 C to 26 C 2c 95 confidence interval 1 year after calibration 2 5x10 19 2 years after calibration lt 5x10 Explanations D After 3 months of continuous operation 2 After 1 year aging during 1 year 5x 19 19 long term lt 2 x 10 10 years 3 After 1 year of operation Uncertainty 6x 107 the first year of operation Calibration Adjustment Tolerance is the maxi mum tolerated deviation from the true 10 MHz freq
173. th 2 5 ns Smart Calculation One pass meas of pulse width single period made with 3 time stamps 2 consecutive pos trig A 1 neg trig A Modes Pos or neg duty factor m Display Main Parameter Duty factor Aux Parameters Period pulse width Vmax 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 8 34 CNT 91 R Measurement Functions DC 1Hz 300 MHz 100 Hz 300 MHz default higher LF limit means higher meas speed Input Frequency Mode Resolution Accuracy typ DC Vmax Vmin Vp p 1 10 mV 1 15 150 mV 1 Hz 1 kHz 196 15 150 mV 1 kHz 20 MHz 3 x 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 Aux Parameters Vmax or Vmin or Vp p Vmin Vp p or Vmax Vp p or Vmin Vmax Totalize A B A B A B A B Inp Freq A B 0 160 MHz Inp Freq E arm 0 80 MHz Range A B 0 to 272 4 24 2410 Main Parameters A B Calc Parameters A B A B A B Modes Manual Gated Start Stop or Timed If A or B is the main parameter A B and A B will be displayed as aux parameters If one of the calculated parameters is the main parameter A and B will be displayed as aux parameters NOTE MANUAL controlled by fron
174. 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 RF Inputs Checking Input C To verify the specification of the different RF prescaler options CNT 90 or the microwave converter in the CNT 90XL use the following basic test setup Connect the output of a signal generator covering the specified frequency range to the RF input of the counter CAUTION Three similar but incompatible coaxial connector standards are used in the CNT 90XL depending on the fre quency range Do not mix them up as abuse might damage the con nectors and cause unexpected results See the specifications in Chapter 8 Connect the 10 MHz REF OUT from the generator to the EXT REF IN on the rear panel of the counter 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 digit will be unstable 7 12 RF Inputs 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 CNT 90 3 GHz Option Frequency Amplitude P F M
175. ting x1 E JLTLU 4 Hyst P OG Q6 IIs 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 6 mV 1 of trig lvl DC tol kHz for other measurement functions Specifications m Timebase Error TBE TBE is the relative error of the timebase oscil lator dimensionless and depends on the ac tual oscillator used See Timebase Options on page 8 30 Total Uncertainty 2c The general formula for all measurement functions is Uv 2 il rand uncert Y syst uncert Time Interval Pulse Width Rise Fall Time m Random Uncertainty rms U nd Eden Error StopTrig Error s m Systematic Uncertainty Us VK Ev 500 ps TBE TIME where Eq trigger level timing error 500 ps maximum channel difference TBE timebase error TIME measurement result Frequency amp Period A B m Random Uncertainty rms For measuring times 200 ms and if Smart Freq AUTO or OFF 2 fe 2 Start Trigger Error x U rnd F 2 Measuring Time x Measurement Result Hz or s CNT 90XL Measurement Uncertainties 8 25 Specifications For measuring times gt 200 ms and if Smart Freq AUTO or ON 2s E 2 Start Trigger Error U 9 x rnd Measuring Time 4
176. tion Uma 2 x presc fact x fi x Eg Esm Essi dimensionless e g ppm Prescaling Factor Input 2 A amp B 16 C 3 GHz 256 C 8 GHz 128 C 15 amp 20 GHz 8 12 CNT 90 Calibration Phase m Typical Random Uncertainty rms NOTE Phase is an auxiliary measurement function intended to give an indication with no guaranteed specification Uma 45 Strt Trg Err Stop Trg Evry xFreq x 360 m Systematic Uncertainty Us Vie Ev 500psy x Freq x360 Duty Factor m Random Uncertainty rms Uma 45 Strt Trg Err Stop Trg Err x Freq or minimum 1 ppm m Systematic Uncertainty Us J LE 200 psy x Freq dimensionless e g ppm 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 Total Uncertainty See also timebase specifications on page 8 15 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 The total possible devia tion from the true 10 MHz frequency under influence of frequency drift due to aging and ambient tem perature va
177. tion 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 trigger level error will always remain to a certain ex tent especially if the temperature conditions are not constant Measuring Functions Totalize CNT 91 R only Totalize in General The Totalize functions add up the number of trigger events on the two counter inputs A and B Several combinations of them are theoreti cally possible Five have been realized and made available by entering the Totalize menu In addition to controlling the gate manually by toggling HOLD RUN you can also open and close the gate by using the arming facilities under SETTINGS The different functions are described below The display is updated continually while the gate is open Events are accumulated during consecutive open periods until RESTART is pressed The manual Totalize functions can not be used in conjunction with the Statistics functions and parameters like block and pac ing Nor does Auto Trigger wor
178. tional Timer Counters The 9X offers the following advantages 12 digits of frequency resolution per sec ond and 100 ps resolution as a result of high resolution interpolating reciprocal counting Optional oven controlled timebase oscilla tors except the CNT 91R which has a fixed ultra stable rubidium oscillator CNT 90 CNT 91 R A variety of RF prescaler options with up per frequency limits ranging from 3 GHz to 20 GHz CNT 90XL A number of microwave inputs with upper frequency limits ranging from 27 GHz to 60 GHz CNT 90 XL Optional built in Li Ion battery supply re 1 2 Preface alizes instant high prescision measure ments in the field and true UPS operation ntegrated 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 the rel ative position in time of measurements with high resolution and accuracy A high measurement rate of up to 250 k readings s to internal memory 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
179. tions Option 10 3 0 GHz Input C Option 13 8 GHz Input C Option 14 15 GHz Input C Option 14B 20 GHz Input C Timebase Op tions not CNT 91R Option 19 90 Option 30 90 Option 40 90 Optional Accessories Medium stability OCXO Very high stability OCXO Ultrahigh stability OCXO Option 11 90 Option 22 90 Option 27 Option 27H Option 29 90 Option 90 01 Option 90 06 Option 90 00 Option 95 03 Option 95 05 Printed Manuals CNT 90 amp CNT 91 R amp CNT 90XL CNT 90 amp CNT 91 R amp CNT 90XL CNT 90 amp CNT 91 R amp CNT 90XL SW Driver on Request Rear panel inputs Rackmount kit Carrying case Heavy duty hard transport case TimeView for CNT 90 91 modulation domain analy sis SW Cal certificate w protocol standard oscillator Cal certificate w protocol oven oscillator Cal certificate w protocol Hold over frequency ag ing week 3 years extended warranty 5 years extended warranty Getting Started Manual User s Manual Programmer s Handbook LabView CNT 91 R Specifications Ordering Information 8 45 Specifications Timebase Options CNT 91 OX Product Family Option Standard Option 19 90 Option 30 90 Option 40 90 Timebase Type UCXO OCXO OCXO OCXO Uncertainty due to Calibration adjustment tolerance 6 8 8 9 23 C 3 C 1x10 5x10 1x10 3x10 Aging per 24 h 1
180. tly 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 measurement is further controlled by the fol lowing elements Manual RESTART if HOLD is selected GPIB tri
181. 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 6688 for calibrating the standard oscillator Reference Oscillator 10 MHz 1 10 e g 6689 for calibrating Opt 30 90 amp Opt 40 90 Voltage Calibrator DC 50 V to 50 V e g 5500 for calibrating the built in 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 lt 3 voltage uncertainty RF Signal Generator 0 1 to 3 8 20 27 40 46 60 GHz dep on RF input 10 MHz ext ref Power Splitter 50 Q 6 dB BNC T piece BNC Termination 50 O feedthrough BNC Low pass Filter 50 kHz for 1 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 low
182. tup mmu 1 2 a 4 g l Next Fig 2 34 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 18 for a complete list of these settings Modify labels Select a memory position to 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 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 Modifu Labels Setup 1 label labc 2 def 3ghij 4klmn Sopqr stuv wxuz E ceed 3 Entering alphanumeric charac ters Using the Controls Dataset Menu Frequency A MATH X 89x MEAS 300 208 256 73 mz User options Save Recall Dataset Recall Erase Fig 2 36 The memory management menu after pressing Dataset This feature is available in statistics mode only and if HOLD has been pressed prior to initiating a measurement with RESTAR
183. ty factor Aux Parameters Period pulse width Vmax 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 Power C Range Power 35 to 10 dBm Frequency 0 3 to 27 40 46 or 60 GHz dep on model Resolution 0 01 dBm 100 ms measuring time Input and Output Specifications 8 19 Specifications Accuracy 1 dBm typ to 27 GHz 2 dBm typ to 40 GHz 3 dBm typ to 60 GHz Acquisition Auto or Manual within 40 MHz Acquisition Time 20 to 30 ms in Auto typ Aux Parameter Frequency C Timestamping A B 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
184. ue Go to the Arming menu SETTINGS Arm and set the seven parameters Arm on Sample Block Decide if each event or each block of events STATISTICS mode should be armed Start Channel Select B Start Slope Select POS marked by a rising edge symbol Start Delay Decide if you need to insert a delay 10 ns 2 s between the control signal and the actual opening of the gate Stop Delay Decide if you need to insert a delay 10 ns 2 s during which the gate will not respond to the control signal on the Stop Channel The main application is to prevent relay contact bounces from closing the gate prematurely Stop Channel Select B Stop Slope Select POS marked by a rising edge symbol m TOT A B Gated by E Select Totalize from the MEAS FUNC menu and then A B Connect the signals to be measured to In puts A and B Set the trigger levels for Inputs A and B manually to suitable values Connect the control signal TTL levels to Input E Go to the Arming menu SETTINGS Arm and set the seven parameters Arm on Sample Block Decide if each event or each block of events STATISTICS mode should be armed Start Channel Select E Start Slope Select POS marked by a rising edge symbol Start Delay Decide if you need to insert a delay Measuring Functions 10 ns 2 s between the control signal and the actual opening of the g
185. ue Press STAT PLOT and watch fmax Frequency Modulated Signals 4 7 Measuring Functions 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 finin Dfp 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 Dfp p Afo fox frin 2xAf Errors in fmax fmin and Dfp p A measurement time corresponding to X cy cle or 36 of the modulation signal leads to an error of approx 1 5 Select the measurement time f lt measure gt 7 Ta 10 x f ncd lation 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 1000 4 8 AM Signals AM Signals The counter can usually measure both the car rier wave frequency and modulation fre quency of AM signals These measurements 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 Fig 4 8 Effects of different sensitivity when measuring the CW Fre quency of a
186. uency after a calibration When the reference frequency does not exceed the tolerance limits at the moment of calibration an adjustment is not needed NOTE Electrical adjustment by means of tun ing voltage from DAC no potentiometer trim ming Serial interface for closed case calibration and status reporting CNT 91 R Timebase Specifications CNT 91R 8 47 Specifications This page is intentionally left blank 8 48 CNT 91 R Timebase Specifications CNT 91R Chapter 9 Index Index Index 1 cyclecounterror 4 9 A AC DC coupling 3 3 Allan deviation seus 6 3 AM modulated signals 4 8 Aperture See Measuring time Arming description 5 5 examples 5 9 manually 5 6 stop delay 2 11 5 3 sync delay 5 7 Attenuator used to reduce noise 3 7 Auto once 1 2 0 eee eee 3 5 Auto Trig Low Freq 2 12 Autotrigger 3 8 4 19 6 4 how OUSE erii ie is Re 3 8 Averaging 4 10 6 2 B Battery Supply checking sse Ren 7 13 Burst Frequency CW 4 5 C Carrier wave frequency AM 4 8 Carrier wave frequency FM 4 6 Channel See Input Confidence limits 6 5 Counterror 1 cycle 4 9 Counting reciprocal 4 9 CW AM uude raa eap ds 4 8
187. urement Time Even if you have chosen a short measurement time this measurement will require between 20 and 40 seconds for this example 4 12 Theory of Measurement m CNT 90 91 R 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 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 12 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 Fig 4 12 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 BurStnin gt presc factor x inp cycle time x3 or at least 80 ns Normally the real minimum limit is set by other fa
188. urst 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 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 amp Arm Select Start Arm Delay 0 and Start Chan E Use MEAS FUNC to select Pulse Width A If there is no or too littl
189. us Single Period Waveform Capture Data Analysis Features Yes 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 Battery Unit Option 23 90 Battery Type Ext DC Input Connector Oper amp Charg Temp Range Storage Operating Time 25 C Charging Charging Time 25 C Status Indicator Weight Li lon 22 2 V 90 Wh 12 to 18 V max 6 A XLR male 3 pin 0 to 40 C 20 to 60 C 1 month 20 to 45 C 3 months 20 to 20 C 1 year ON gt 4 5 h Stby gt 24 h Automatic when ext AC or DC is connected lt 8 5 h On screen w low battery warning 1 2 kg Measurement Uncertainties Random Uncertainties 10 m Quantization Error Eq Eq 100 ps rms m Start Stop Trigger Error Ess 2 2 Ess Fhoise ES E jitter s l e RENE S NER noise input noise signal y l s inp sign slew rate A at trig point noise Ej Single Period Jitter rms s Vnoise input 500 uVrms internal noise 200 Vrms typical The rms noise of the applied signal Vnoise signal Systematic Uncertainties m Trigger Level Timing Error Et Time Interval Rise Fall Time Pulse Width Duty Factor Phase attenuator set
190. ve 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 Activate start arming by keying in the fol lowing sequence SETTINGS Arm Start Chan OFF GE 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 7 10 Measuring Functions 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 O 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 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 impedance DC coupling MANual trigger x1 attenuation
191. ve 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 Input 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 measure
192. vice Sales and Service Office 10 2 11 Appendix New Look ee Rib Res 11 2 VII GENERAL INFORMATION About this Manual This manual contains directions for use that apply to the Timer Counter Analyzers CNT 90 and CNT 91 as well as the Frequency Calibrator Analyzer CNT 91R and the Microwave Coun ter Analyzer CNT 90XL In order to simplify the references these instruments are further referred to throughout this man ual as the OX whenever the information applies to all types Differences are clearly marked Examples e CNT 90 91 means CNT 90 and CNT 91 CNT 91 R means CNT 91 and CNT 91R Chapter 8 Specifications is divided into three separate sections to increase legibility Much of the contents is common so redundant data is the price in this case Warranty The Warranty Statement is part of the folder Important Information 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 VIII Chapter 1 Preparation for Use Preparation for Use Preface Introduction Congratulations on your choice of instrument It will serve you well and stay ahead of most competition for many years to come Your instrument is designed to bring you a new dimension to bench top and system counting It gives significantly increased per formance compared to tradi
193. ween 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 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
194. x of a sampled population of N xi values and is calculated as N X 1 Xi Nin 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 x 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 2 1 0 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 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
195. x360 m Systematic Uncertainty Usu A5 EP 500psy x Freq x 360 8 42 CNT 91 R Measurement Uncertainties Duty Factor m Random Uncertainty rms Uma Ee Strt Trg Err Stop Trg Err x Freq or minimum 1 ppm m Systematic Uncertainty U ss Jx Eu m 200 psy x Freq dimensionless e g ppm 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 Specifications 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 specification See also timebase specifications on page 8 46 General Specifications Environmental Data Class MIL PRF 28800F Class 3 0 C to 50 45 C 40 C to 71 C non con densing lt 12000 m Operat Temp Storage Temp Humidity 5 95 10 30 C 5 75 30 40 C 5 45 40 50 45
196. y 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 TimeView software package will do this measurement quickly and easily i wh Voltage step generator Input E Ext Arm Input A Fig 5 16 Setup for transient profiling of a VCO ig Help View Print Conf Mz FREQUENCY A Rep Samp i i 58 1800 158 581 Sanples 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 t
197. yed in the course of the data capture Thus it can take quite some time if the setting of the counter is not optimal Here are a few tips to speed up the process 6 4 Statistics 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 measurements 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 Fig 6 1 Jitter and drift 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 1 contains a slower varia tion as w

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