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MODEL SR620

1. The strip chart of the mean for the D A scan 30 is shown here In this case the VCO C x 25 frequency decreases as i the control voltage Q increases x 20 uo The cursor shows a 5 frequency of 1 9632 g 15 MHz at the 104th point in the scan en S a he ge er se L voltage on the x axis and the measured frequency on the y axis Of course hardcopy of the scope display which shows the linearity curve may be printed or plotted EXAMPLE OF A TIME SCAN In this example the frequency of a VCO is measured as a function of time after the control voltage is stepped The front panel 1 kHz REF OUT serves as the EXT trigger and as a trigger to the pulse generator that stepped the voltage to the VCO An internally generated 1 us gate will be scanned in 1 us increments to record the frequency of the VCO as a function of time on successive triggers Clearly for this sampling technique to work the frequency of the VCO needs to be reproducible from trigger to trigger The SR620 should be setup to measure the frequency of the A input It is important to select an EXTernal gate in the GATE ARM section The EXT LED will blink when the Delay Scan is enabled in the CONFIG menu Set the SAMPLE SIZE to 10 and choose the MEAN for the scope display Select TTL for the REF OUT level and adjust the EXT trigger input threshold to 1 volt rising edge Use autolevel for the A input l l l l l l l i
2. Parts List 93 REF SRS PART VALUE DESCRIPTION C914 5 00098 517 10U Capacitor Tantalum 35V 20 Rad C915 5 00098 517 10U Capacitor Tantalum 35V 20 Rad C 916 5 00098 517 10U Capacitor Tantalum 35V 20 Rad C 917 5 00098 517 10U Capacitor Tantalum 35V 20 Rad C 918 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 920 5 00100 517 2 2U Capacitor Tantalum 35V 20 Rad C 950 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 951 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 952 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 953 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 954 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 955 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 956 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 957 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 958 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 959 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 960 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 961 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 962 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 963 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 964 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 965 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 966 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 967
3. for j 0 j lt 4 j words j words j take 1 s complement convert to floating point for j 0 j lt 4 j fdata i fdata i 65536 0 double words 3 j SR620 Universal Time Interval Counter 54 Programming Examples if number is negative add 1 to get 2 s complement and change sign if sign fdata i 1 0 fdata i 1 0 now multiply by conversion factor fdata i factors mode fdata i if expd fdata i fdata i 1 0E 3 reduce by 1000 if expand is on kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk void InitGpib void initialize the CEC GPIB card as controller int my_address system_controller unsigned seg find cec card address for seg 0x4000 seg lt 0xF000 seg 0x400 if peek Seg 50 C amp amp peek seg 51 E amp amp peek seg 52 C break if pc488_seg seg printf no gpib card installed n exit 0 my_address 21 system_controller 0 initialize amp system_controller amp my_address transmit amp status IFC UNT UNL DCL REN kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk void TalkGpib int address makes device at address a talker char cmd 25 sprintf cmd UNT UNL MLA TALK d address transmit amp status cmd StatCheck address kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
4. l 1 l l l l l SR620 Universal Time Interval Counter 22 Configuration Menus Now use the CONFIG section to setup the scan Press the SEL key to select the Scn menu Press the SET key and use the SCOPE AND CHART up down keys to setup the scan parameters as follows Scan Configuration Menu for Example Line Display Function 1 ScAnEnA rEPEAt Enable repeated scans 2 ScAnPtsS 250 Set 250 points per scan 3 hoLd 0 01 S Set minimum hold time 4 dA Src chrt chrt DefaultbD A functions 5 dA Can t set D A voltages 6 Step Not stepping D A s 7 GELAy ScAn ScAn Enable delay scans 8 gAtE StEP 1E 6 1 us gate width amp step 9 StArt 0 000001 Start scan delay at 1 us The strip chart of the mean for the time scan is shown here A pulse of 100 us duration delayed by 100 us from the EXT trigger was applied to the VCO input of an RC oscillator The scan shows the transient frequency response of the oscillator Frequency x 104 Hz The cursor indicates a frequency of 77 34203 kHz at 210 us after the EXT trigger input SR620 Universal Time Interval Counter 0 Hz 7 34203 kHz Then press the RESET key in the SAMPLE SIZE section to exit from the CONFIG menus The SR620 will compose a scope display showing the frequency of the VCO as a function of time after the rising edge of the REF OUT If the oscillator stops then the scan will stop The AUTO key in the SCOPE AND C
5. Autolevel A amp B Slope Impedance Coupling Input Noise Bandwidth Prescaler A amp B Protection REF Output Frequency Rise Fall Amplitude DVM Inputs Full Scale Type Impedance Accuracy Speed D A Outputs Full Scale Resolution Impedance 0 01 seconds 1 period min for period measurement and 1 sample for time interval measurement Period may also be measured using externally triggered internal gates as in frequency mode lt 1ns x Frequency x 360 0 001 degree 1012 RATIO A B range 10 9 to 103 0 to 300 MHz Same as frequency 12 digits Standard Option 01 10 000 MHz 10 000 MHz TCVCXO Ovenized VCXO 1x106 yr 5x10 10 day 3x10 10 5x10 12 1 ppm 0 002 ppm 0 01 ppm 0 001 ppm User may supply 5 or 10 MHz timebase 1 Volt nominal A B and EXTernal 5 00 to 5 00 VDC with 10 mV resolution 15mV 0 5 of setting see graph next page Threshold set between peak input excursions f gt 10 Hz duty cycle gt 10 Rising or falling edge 1 M Ohm 30 pf or 50 Ohms 50 Ohm termination has SWR lt 2 5 1 from 0 1 3GHz AC or DC Ext is always DC coupled 350mV rms typical 300 MHz BW provides 1 2 ns risetime see graph next page 100 V 50 Ohm terminator is released if input exceeds 5 Vpeak Calibration and Trigger source 1 00 KHz Accuracy same as timebase 2ns TTL 0 to 4 VDC 2 VDC into 50 Ohms ECL 1 8 to 0 8 VDC into 50 Ohms Two differential rear panel DVM inputs
6. Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg 103 SR620 Universal Time Interval Counter 104 Parts List REF SRS PART VALUE U 203 3 00044 340 74HC244 U 204 3 00046 340 74HC374 U 205 3 00046 340 74HC374 U 206 3 00046 340 74HC374 U 207 3 00046 340 74HC374 U 208 3 00046 340 74HC374 U 209 3 00064 340 CA3081 U 210 3 00264 340 MPQ3467 U 211 3 00264 340 MPQ3467 U 222 3 00491 340 UPD71054C U 230 3 00151 340 MC10125 U 231 3 00238 340 74F74 U 232 3 00238 340 74F74 U 233 3 00044 340 74HC244 U 234 3 00046 340 74HC374 U 235 3 00046 340 74HC374 U 236 3 00046 340 74HC374 U 237 3 00265 340 74HC595 U 238 3 00265 340 74HC595 U 239 3 00264 340 MPQ3467 U 241 3 00049 340 74HC74 U 242 3 00171 340 74HC191 U 243 3 00207 340 74F191 U 244 3 00238 340 74F74 U 245 3 00049 340 74HC74 U 250 3 00265 340 74HC595 U 301 3 00117 325 78L12 U 301A 3 00116 325 78L05 U 303 6 00051 622 10 MHZ U 304 3 00266 340 MC10H116 U 305 3 00294 340 AD96685 U 309 3 00151 340 MC10125 U 311 3 00194 340 MC10H131 U 312
7. overflow 3 unused 4 Execution err Set by an out of range parameter or non completion of some command due a condition like overload 5 Command err Set by a command syntax error or unrecognized command 6 URQ Set by any key press or trigger knob rotation 7 PON Set by power on This status byte is defined by IEEE 488 2 1987 and is used primarily to report errors in commands received over the communications interfaces The bits in this register stay set once set and are cleared by reading them or by the CLS command TIC Status Byte bit name usage 0 Ext Trig Set when the external trigger comparator switches 1 A trig Set when the A channel trigger comparator switches 2 B trig Set when the B channel trigger comparator switches 3 arm Set when the SR620 becomes armed 4 Ext Ovid Set by Ext input overload condition 5 A Ovld Set by A input overload condition 6 B Ovid Set by B input overload condition 7 unused These bits stay set until cleared by reading or by the CLS command Error Status Byte bit name usage Set when an error is detected during printing plotting Set when the 10 MHz clock signal is not present Set when A channel autolevel looses the trigger and tries to find a new trigger level Set when B channel autolevel looses the trigger and tries to find a new trigger level Set when the self test routine detects an error O print error 1 noclock 2 A autolevel 3 B a
8. 1N5711 D 403 3 00203 301 1N5711 D 404 3 00403 301 1N459A D 405 3 00403 301 1N459A D 422 3 00203 301 1N5711 D 423 3 00203 301 1N5711 SR620 Universal Time Interval Counter DESCRIPTION Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Electrolytic 16V 20 Rad Capacitor Electrolytic 16V 20 Rad Capacitor Electrolytic 16V 20 Rad Capacitor Electrolytic 35V 20 Rad Capacitor Electrolytic 35V 20 Rad Capacitor Electrolytic 35V 20 Rad Capacitor Electrolytic 35V 20 Rad Capacitor Ceramic Disc 50V 10 SL Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode
9. Metal Film 1 8W 0 1 25ppm R 819 4 00432 407 56 2K Resistor Metal Film 1 8W 1 50PPM R 821 4 00138 407 10 0K Resistor Metal Film 1 8W 1 50PPM R 822 4 00057 401 220 Resistor Carbon Film 1 4W 5 SR620 Universal Time Interval Counter 102 Parts List REF SRS PART VALUE R 823 4 00138 407 10 0K R 824 4 00138 407 10 0K R 825 4 00057 401 220 R 826 4 00138 407 10 0K R 827 4 00031 401 100 R 830 4 00176 407 3 01K R 831 4 00035 401 10M R 832 4 00035 401 10M R 833 4 00035 401 10M R 834 4 00035 401 10M R 839 4 00035 401 10M R 840 4 00035 401 10M R 841 4 00035 401 10M R 842 4 00035 401 10M R 843 4 00138 407 10 0K R 845 4 00138 407 10 0K R 846 4 00278 407 10 7K R 847 4 00021 401 1 0K R 848 4 00034 401 10K R 849 4 00034 401 10K R 850 4 00158 407 2 00K R 851 4 00138 407 10 0K R 852 4 00467 407 2 43K R 853 4 00031 401 100 R 860 4 00034 401 10K R 861 4 00034 401 10K R 901 4 00436 409 0 1 R 902 4 00021 401 1 0K R 903 4 00437 401 27K R 904 4 00059 401 22K R 905 4 00034 401 10K R 906 4 00034 401 10K R 907 4 00372 431 50 30 25 R 908 4 00079 401 4 7K R 909 4 00048 401 2 2K R 910 4 00034 401 10K R 911 4 00436 409 0 1 R 912 4 00021 401 1 0K R 913 4 00437 401 27K R914 4 00059 401 22K R915 4 00138 407 10 0K R 916 4 00470 407 10 5K R 921 4 00436 409 0 1 R 922 4 00021 401 1 0K R 923 4 00437 401 27K R 924 4 00059 401 22K R 925 4 00138 407 10 0K R 926 4 00185 407 4 02K R 931 4 00059 401 22K R 932 4 00034 401 10K R 93
10. R1A 4 00555 407 590 R 101 4 00079 401 4 7K R 102 4 00021 401 1 0K R 103 4 00034 401 10K R 104 4 00034 401 10K R111 4 00021 401 1 0K R 112 4 00021 401 1 0K R 113 4 00057 401 220 R 114 4 00057 401 220 R 115 4 00140 407 10 2K R 116 4 00188 407 4 99K R 123 4 00021 401 1 0K R 124 4 00021 401 1 0K R 125 4 00080 401 47 R 126 4 00080 401 47 R 127 4 00079 401 4 7K R 128 4 00048 401 2 2K R 129 4 00138 407 10 0K R 130 4 00493 407 12 4K R 131 4 00051 401 2 7K R 132 4 00032 401 100K R 133 4 00022 401 1 0M R 134 4 00062 401 270 R 201 4 00471 401 82 R 202 4 00314 401 12 R 203 4 00081 401 470 R 204 4 00081 401 470 R 205 4 00314 401 12 R 225 4 00130 407 1 00K R 226 4 00061 401 240K R 229 4 00191 407 49 9 R 230 4 00191 407 49 9 R 231 4 00191 407 49 9 R 232 4 00490 407 27 4 R 233 4 00462 407 39 2 R 234 4 00048 401 2 2K R 235 4 00021 401 1 0K R 236 4 00057 401 220 R 237 4 00272 407 221 R 238 4 00032 401 100K R 239 4 00073 401 330K R 240 4 00031 401 100 R 241 4 00031 401 100 R 305 4 00048 401 2 2K R 317 4 00030 401 10 R 318 4 00030 401 10 R 325 4 00021 401 1 0K R325A 4 00086 401 51 R 326 4 00062 401 270 R 327 4 00031 401 100 R 328 4 00048 401 2 2K SR620 Universal Time Interval Counter DESCRIPTION Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Fil
11. Rectangular D 50 3 00004 301 1N4148 Diode D 51 3 00012 306 GREEN LED Rectangular D 52 3 00884 306 RED LED Rectangular D 53 3 00012 306 GREEN LED Rectangular D 54 3 00012 306 GREEN LED Rectangular D 55 3 00012 306 GREEN LED Rectangular D 58 3 00012 306 GREEN LED Rectangular D 59 3 00012 306 GREEN LED Rectangular D 60 3 00004 301 1N4148 Diode D 61 3 00884 306 RED LED Rectangular D 62 3 00012 306 GREEN LED Rectangular D 63 3 00012 306 GREEN LED Rectangular D 64 3 00012 306 GREEN LED Rectangular D 65 3 00012 306 GREEN LED Rectangular D 66 3 00012 306 GREEN LED Rectangular D 67 3 00012 306 GREEN LED Rectangular D 68 3 00012 306 GREEN LED Rectangular D 69 3 00012 306 GREEN LED Rectangular D 70 3 00004 301 1N4148 Diode D 71 3 00012 306 GREEN LED Rectangular D 72 3 00012 306 GREEN LED Rectangular D 73 3 00012 306 GREEN LED Rectangular D 74 3 00012 306 GREEN LED Rectangular D75 3 00012 306 GREEN LED Rectangular D 76 3 00012 306 GREEN LED Rectangular D 77 3 00012 306 GREEN LED Rectangular D 78 3 00012 306 GREEN LED Rectangular D79 3 00012 306 GREEN LED Rectangular D 80 3 00004 301 1N4148 Diode D 81 3 00012 306 GREEN LED Rectangular D 83 3 00012 306 GREEN LED Rectangular D 84 3 00012 306 GREEN LED Rectangular D 86 3 00012 306 GREEN LED Rectangular D 87 3 00012 306 GREEN LED Rectangular D 88 3 00012 306 GREEN LED Rectangular D 89 3 00012 306 GREEN LED Rectangular J 261 1 00073 120 INSL Connector BNC J 401 1 000
12. Set D A 0 to 0 V 2 Adjust calbyte 16 until the meter reads within 5mv of zero 3 Attach the voltmeter to D A 1 Set D A 1 to OV 4 Adjust calbyte 17 until the meter reads within 5 mV of 0 D A Output Gain Calibration 4 Attach the voltmeter to D A 0 Set D A 0 to 10V Set calbyte 18 to 1 Measure the output voltage Gain factor 10 0 V Calculate calbyte 18 as follows a Ifthe gain is less than 1 multiply the gain factor by 65536 and round even b If the gain is greater than or equal to 1 multiply the gain factor by 65536 and round odd Repeat 1 3 with output 1 to get calbyte 19 DVM Input Calibration 9 Attach a stable dc source to DVM input O and to the voltmeter Set the DVM 0 input range to 20V Set the dc source to 0 Adjust calbyte 20 until the DVM 0 reading and the voltmeter reading agree Set the dc source to about 18 V Adjust calbyte 24 until the DVM 0 reading and the voltmeter agree Set the DVM 0 input range to 2V and the dc source to 0 Adjust calbyte 22 until the DVM 0 reading and the voltmeter agree Set the dc source for about 1 8V 10 Adjust calbyte 26 until the DVM 0 reading and the voltmeter agree 11 Repeat 1 10 for DVM input 1 to get values for calbytes 21 25 23 and 27 Calibration Procedure 73 SR620 Universal Time Interval Counter 74 Calibration Procedure SR620 Universal Time Interval Counter Circuit Description 75 SR620 CIRCUIT
13. This input presents a 1 kOhm load to the signal The SR620 can then phase lock its internal timebase to this external source See the CONFIGURATION MENU chapter for detail on using an external timebase DVM INPUTS The SR620 has two rear panel DVM inputs These 1 MOhm differential inputs allow the SR620 to measure DC voltages on either a 2V or 20V full scale range The SR620 can either autorange the inputs default or they may be set to a fixed scale See the CONFIGURATION MENU chapter for detail on setting the DVM scales Sample Arming _11 SAMPLE ARMING The SR620 Time Interval counter has a wide variety of arming modes that allow the user great flexibility in controlling the desired measurement The various measurement modes and their respective arming modes are discussed in detail below NOTE references to delayed or scanning gates are discussed at the end of this section TIME MODE In this mode the unit measures the time interval between a Start and a Stop pulse The time interval is a positive number if the Start occurs before the Stop and negative if the Stop occurs before the Start The SOURCE LED s indicate the source of the START pulse Source LED Start Source Stop Source A A B B B A REF REF B The knobs which are directly above each input set the voltage threshold for that input when in the TIME mode Usually A will be selected as the Start source and the time interval from A to B will be measur
14. Washer Split Wire 18 UL1007 Stripped 3 8x3 8 No Tin Wire 24 UL1007 Strip 1 4x1 4 Tin Wire 24 UL1007 Strip 1 4x1 4 Tin Wire 24 UL1007 Strip 1 4x1 4 Tin Wire 22 UL1007 Wire 24 UL1007 Strip 1 4x1 4 Tin Wire 424 UL1007 Strip 1 4x1 4 Tin Grommet Fans amp Hardware Insulators Screw Flathead Phillips Screw Panhead Phillips Screw Panhead Phillips Screw Flathead Phillips Washer nylon Screw Black All Types Insulators Window Washer nylon Wire 22 UL1007 Wire 422 UL1007 Wire 422 UL1007 Wire 422 UL1007 Screw Black All Types Termination Hardware Misc Spacer Wire 18 UL1015 Strip 3 8 x 3 8 No Tin Wire 424 UL1007 Strip 1 4x1 4 Tin Connector Amp MTA 100 Thru hole Pkg Thru hole Pkg ee a gta REF SRS PART VALUE ZO 1 00261 130 1 PIN Zo 1 00262 130 3 PIN Z0 5 00262 548 01U AXIAL ZO 6 00004 611 1A 3AG Zo 6 00017 630 FB43 301 Z0 6 00213 630 2 HOLE ZO 7 00151 735 SR620 23 ZO 7 00157 709 SR620 30 33 ZO 7 00165 720 SR620 43 44 45 ZO 7 00168 720 SR620 37 ZO 7 00170 720 SR620 40 ZO 7 00176 720 SR620 46 ZO 7 00195 720 SR620 47 ZO 7 00722 709 SR620 54 ZO 9 00184 917 SR620 SERIAL ZO 9 00552 924 COPPERFOIL 1 Miscellaneous Parts List REF SRS PART VALUE U 103 3 00345 342 27C512 120 ZO 0 00179 000 RIGHT FOOT ZO 0 00180 000 LEFT FOOT ZO 0 00185 021 6 32X3 8PP ZO 0 00204 000 REAR FOOT ZO 0 00248 026 10 32X3 8TRUSSP ZO 0 00251 004 SR620 49 ZO 0 00271
15. data is buffered by U128 an LS octal transceiver Output control bits are buffered by the open collector driver U127 and input control bits are discriminated by 1 4 and 2 4 of U125 The printer port may be used as a general purpose digital I O port Normally the bit Print Init is used to initialize the printer when brought low and configure the octal buffer for output when set high However with this bit set low the Z8800 can read data which is present at the printer port SR620 Universal Time Interval Counter 76 Circuit Description GPIB amp RS232 commands support these functions RS 232 INTERFACE Sheet 2 of 16 The Z8800 UART output is buffered by 1 4 of U126 to send data from the instrument to a host computer The RS 232 received data is buffered by 3 4 of U125 and sent to the Z8800 UART input The Z8800 can set the bit RS232CTS low to tell the host computer that is okay to send data The RS232 bits DSR and CD are always high The signal from the host computer DTR Data Terminal Ready may be used to stop RS232 data output if DTR goes low The SR620 is a DCE and may be connected to PC s using a standard serial cable not a null modem cable SCOPE DISPLAY Sheet 3 of 16 Rear panel outputs provide voltages to display histograms and graphs on an XY oscilloscope The xy coordinates are stored in a list in the 8Kx8 static RAM U117 This RAM may be written to or read from by the Z8800 Access to the RAM is
16. line is used to select the representation for the jitter values Either a standard deviation root of the mean squared deviation ie rms or the root Allan variance may be displayed The gAtE ScAIE line will appear in frequency period and count modes The actual gate time for a sample is equal to the front panel gate time setting multiplied by the gate scale For example with a gate time of 0 01s and a gate scale of 5E 3 the actual gate time will be 0 01s x 5E 3 50ms If the gate scale is set to other than the default of 1 the gate time LED will blink Gate scales ranging from 1E 4 to 500 allow 1ms to 500s gates The trig ScAle line allows the setting of the full scale range of the trigger knobs to either 1 25 2 50 or 5 00 volts This allows small trigger levels to be set more easily The resolution is 10mV in all cases This setting does not affect the trigger level range over the communications interfaces SCAN MENU Scn The SR620 has a scanning capability that allows automatic measurement of VCO tuning curves oscillator step response etc The SR620 can at the end of each measurement of N points automatically step either or both of its d a output voltages and its external trigger delay see ARMING section The D A scans allow measurements of timing frequency phase etc versus an applied voltage Example the frequency of a VCO as a function of Voltage The D A outputs may also be set to fixed values in
17. scan One should use the SCLR and STRT commands instead Time 2 712673611111111 E 12 256 1 05963812934 E 14 Width 2 712673611111111 E 12 256 1 05963812934 E 14 Rise fall time Frequency Frequency 2 712673611111111 E 12 256 1 05963812934 E 14 1 0 E 12 2 71267361111111 2468 1 24900090270331 E 9 x1000 OFF 1 0 E 9 2 71267361111111 2468 1 24900090270331 E 12 x1000 ON Period 2 712673611111111 E 12 256 1 05963812934 E 14 x1000 OFF Period 2 712673611111111 E 15 256 1 05963812934 E 17 x1000 ON Phase 360 000 2432 8 3819032 E 8 Count 1 256 Ratio 1 2440 9 094947017729282 E 13 SR620 Universal Time Interval Counter Programming Commands 35 SCEN j The SCEN command controls the enable status of the SR620 s scanning features If j 0 scanning is disabled If j 1 the scan mode is set to SINGLE In this mode the unit will automatically stop taking data when a scan is complete If j 2 the scan mode is set to REPEAT and the unit will automatically restart the scan when the present scan is complete SCLR The SCLR command clears but does not start a scan SLOC The SLOC query returns the number of the last completed scan point If no points have been taken or scans are not enabled SLOC return the value 0 SCPT j The SCPT command sets the number of points in a scan The number may be set to one of 2 5 10 25 50 125 or 250 points VBEG j x The VBEG command
18. 000 BUMPER ZO 0 00283 000 BUMPER1 ZO 0 00292 026 6 32X3 16 TRUSS Zo 0 00315 021 6 32X7 16 PP Zo 1 00087 131 2 PIN JUMPER Z0 7 00169 720 SR620 39 ZO 7 00171 720 SR620 41 ZO 7 00172 720 SR620 42 Parts List 107 DESCRIPTION Connector Male Connector Male Capacitor Ceramic 50V 80 20 Z5U AX Fuse Ferrite Beads Ferrite Beads Injection Molded Plastic Lexan Overlay Fabricated Part Fabricated Part Fabricated Part Fabricated Part Fabricated Part Lexan Overlay Product Labels Tape All types DESCRIPTION EPROM PROM I C Hardware Misc Hardware Misc Screw Panhead Phillips Hardware Misc Screw Black All Types Knobs Hardware Misc Hardware Misc Screw Black All Types Screw Panhead Phillips Connector Female Fabricated Part Fabricated Part Fabricated Part SR620 Universal Time Interval Counter 108 Parts List SR620 Universal Time Interval Counter
19. 00023 529 1U C 807 5 00023 529 1U C 811 5 00023 529 1U C 812 5 00008 501 22P C 813 5 00023 529 1U C 814 5 00023 529 1U C 815 5 00023 529 1U C 816 5 00002 501 100P C 817 5 00023 529 1U C 818 5 00002 501 100P C 819 5 00023 529 1U C 821 5 00127 524 2 2U C 822 5 00023 529 1U C 823 5 00023 529 1U C 824 5 00127 524 2 2U C 825 5 00023 529 1U C 826 5 00127 524 2 2U C 827 5 00162 519 2200P C 828 5 00163 566 3900P C 829 5 00131 501 560P C 830 5 00127 524 2 2U C 831 5 00054 512 047U C 832 5 00054 512 047U C 833 5 00008 501 22P C 834 5 00054 512 047U C 835 5 00054 512 047U C 836 5 00008 501 22P C 901 5 00098 517 10U C 902 5 00098 517 10U C 903 5 00098 517 10U C 904 5 00002 501 100P C 905 5 00002 501 100P C 906 5 00002 501 100P C 907 5 00102 517 4 7U C 908 5 00023 529 1U C 909 5 00098 517 10U C 910 5 00192 542 22U MIN C 911 5 00192 542 22U MIN C 912 5 00127 524 2 2U SR620 Universal Time Interval Counter DESCRIPTION Capacitor Polystyrene 50V 5 Rad Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Ceramic Disc 50V 10 SL Cap Monolythic Ceramic 50V 20 Z5U Cap Polyester Film 50V 5 40 85c Rad Capacitor Polystyrene 50V 5 Rad Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Polystyrene 50V 5 Rad Cap Monolythic Cer
20. 232 UART is garbage from when the SR620 was turned ON It is good practice to send a few carriage returns to the SR620 to flush its command queue Also your program should read and ignore any characters which may be left in the computer s UART 4 The SR620 is not sending the correct end of record marker for your computer For example it appears that some FORTRANs 5 require two carriage returns for an end of record marker The ENDT command may be used to set the end of record sequence The end of record marker is that sequence which indicates a response is complete From a keyboard a single carriage return is the end of record marker Answers are coming back from the SR620 to fast overwriting previous responses before the computer can get them To increase the dwell time between characters use the WAIT n command The dwell time between characters will be 2n ms The RS 232 echo must be OFF otherwise all characters sent to the SR620 will be echoed back to the source See the section on Configuration Menus for details on RS232 configuration The computer will most likely confuse echoed commands with the desired data SR620 Universal Time Interval Counter 60 Troubleshooting Tips SR620 Universal Time Interval Counter PERFORMANCE TESTS INTRODUCTION The procedures in this section test the performance of the SR620 and compare it to the specifications in the front of this manual The first set of
21. 3 00266 340 MC10H116 U 313 3 00266 340 MC10H116 U 314 3 00194 340 MC10H131 U 315 8 00073 860 SR531 ASSY U 316 3 00105 340 LM741 U 317 3 00185 340 LM2901 U 318 3 00076 340 DG211 U 401 3 00196 335 HS 212S 5 U 402 3 00126 335 1A05 U 403 3 00554 340 SP4633 U 404 3 00066 340 CA3140E U 405 3 00196 335 HS 212S 5 U 406 3 00087 340 LF347 U 407 3 00143 340 LM393 U 408 3 00294 340 AD96685 U 410 3 00196 335 HS 212S 5 U 412 3 00126 335 1A05 U 413 3 00554 340 SP4633 SR620 Universal Time Interval Counter DESCRIPTION Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Transistor TO 92 Package Transistor TO 92 Package Ovenized Crystal Oscillator Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole
22. 330 5 00017 501 47P C 331 5 00002 501 100P C 332 5 00002 501 100P C 333 5 00023 529 1U C 334 5 00023 529 1U C 401 5 00023 529 1U C 402 5 00104 530 3 5 20P C 403 5 00023 529 1U C 404 5 00023 529 1U C 405 5 00002 501 100P C 406 5 00062 513 0022U SR620 Universal Time Interval Counter DESCRIPTION Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Cap Polyester Film 50V 5 40 85c Rad Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Capacitor Tantalum 50V 20 Rad Capacitor Tantalum 50V 20 Rad Capacitor Tantalum 50V 20 Rad Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Capacitor Tantalum 50V 20 Rad Capacitor Ceramic Disc 50V 10 NPO Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 50V 20 Rad Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 50V 20 Rad Capacitor Tantalum 50V 20 Rad Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Ceramic Disc 50V 10 SL Cap Monolythic Ceramic 50V 20 Z5U Capacitor Ceramic Disc 50V 10 SL Capacitor Cera
23. Capital Equipment Co GPIB card The CEC cards DMA input routine is used to directly put the data into the PC s memory All of the interface routines to the CEC card reside in firmware on the card 10 program to test TIC binary dump mode this program will binary dump 20 samples from the time interval counter and convert the binary values to 30 numbers in units appropriate to the measurement mode The program 40 demonstrates sending and receiving simple commands from the TIC The 50 program uses the GPIB interface and a Capital Equipment Co GPIB interface 60 card 70 This program runs in interpreted IBM PC Basic 80 DIM DAT 16000 FDATA 2000 FACTORS 7 TEMP 4 90 DATA 1 05963812934D 14 1 05963812934D 14 1 05963812934D 14 100 DATA 1 24900090270331D 9 1 05963812934D 14 8 3819032D 8 0 00390625D0 110 FOR I 1 TO7 120 READ FACTORS I 130 NEXT 140 DEF SEG amp HDOOO base address of CEC card 150 INIT 0 TRANSMIT 3 SEND 9 ENTER 21 DMA2 206 CEC subroutine offsets 160 ADDR 21 SYS 0 controller address 170 SR620 16 TIC address 180 190 string definitions 200 IN IFC UNT UNL REN clear interface 210 BD BDMP 220 MD mode 230 TALK UNT UNL MLA TALK 16 240 EXPD expd 250 260 CALL INIT ADDR SYS init CEC card 270 280 PRINT Enter number of samples lt cr gt to quit 290 INPUT gt S get number of samples 300 SAMPLES VAL S 310 IF SA
24. Diode Diode Diode Diode Diode Diode Diode Diode Parts List 95 REF SRS PART VALUE D 424 3 00403 301 1N459A D 425 3 00403 301 1N459A D 444 3 00403 301 1N459A D 445 3 00403 301 1N459A D 461 3 00203 301 1N5711 D 801 3 00004 301 1N4148 D 802 3 00004 301 1N4148 D 902 3 00004 301 1N4148 D 1001 3 00226 301 1N5822 D 1002 3 00226 301 1N5822 D 1003 3 00226 301 1N5822 D 1004 3 00226 301 1N5822 D 1005 3 00062 340 KBP201G BR 81D D 1006 3 00062 340 KBP201G BR 81D D 1007 3 00062 340 KBP201G BR 81D D 1020 4 00541 435 130V 1200A DL301 0 00051 056 RG174 DL501 0 00051 056 RG174 DL601 0 00051 056 RG174 DL602 0 00051 056 RG174 J 111 1 00003 120 BNC J112 1 00003 120 BNC J121 1 00238 161 GPIB SHIELDED J 122 1 00016 160 RS232 25 PIN D J 123 1 00016 160 RS232 25 PIN D J 201 1 00038 130 40 PIN DIL J 301 1 00003 120 BNC J 303 1 00003 120 BNC J 806 1 00073 120 INSL J 807 1 00073 120 INSL J 808 1 00003 120 BNC J 809 1 00003 120 BNC LIA 6 00192 603 8 2UH L 221 6 00030 602 470UH L 303 6 00049 601 16UH L 304 6 00049 601 16UH L 305 6 00048 603 4 7UH L 306 6 00049 601 16UH L 307 6 00049 601 16UH L 308 6 00048 603 4 7UH L 901 6 00028 604 10UH N 101 4 00334 425 10KX5 N 121 4 00284 421 1 0KX4 N 201 4 00334 425 10KX5 N 202 4 00419 420 150X8 N 203 4 00468 420 300X8 N 204 4 00468 420 300X8 N 205 4 00468 420 300X8 N 206 4 00551 420 12X8 N 213 4 00266 421 4 7KX3 N 214 4 00291 421
25. Error Messages Common Operational Problems Error Messages Error Indicators Wrong Value Excessive Jitter Scope Display Problems Printer and Plotter Problems GPIB Interface Problems RS 232 Interface Problems Performance Tests Necessary Equipment Functional Tests Front Panel Test Self Test Trigger Input Tests Counter Channel Tests Rear Panel Tests Performance Tests Timebase Frequency Accuracy Time Interval Trigger Sensitivity Trigger Accuracy D A Output Accuracy DVM Input Accuracy Test Scorecard Calibration Overview Calibration Bytes Simple Calibration Complete Calibration Trigger Input Calibration Clock Oscillator Calibration Insertion Delay Calibration D A Output Calibration DVM Input Calibration SR620 Circuitry Circuit Description Processor System GPIB Interface Printer Interface RS 232 Interface Scope Display Counter Input Ports Display Control Ports Front End Status Bits ADC and DAC Control Bits REF OUT Delay and Gate Generator 69 69 69 Table of Contents iii Timebase 79 Front End Inputs 79 Trigger Multiplexers 80 Frequency Gates 80 Event Gating 81 Counting Channels 81 Fast Time Interval Logic 82 Time Interval Arming 82 Time Integrators 83 Analog to Digital Converter 83 Autolevel Circuits 83 Digital to Analog Converter 84 Unregulated Power Supplies 84 Power Supply Regulators 84 Power Supply Bypass 85 Front Panel Display PCB 85 Component Parts List 87 Schematic Circ
26. GetGpib address rstring integer 2 address status length character 40 rstring character 40 cmd write cmd 100 address 100 format UNT UNL MLA TALK 12 call TRANSMIT cmd status call StatCheck address status rstring 1 40 call RECEIVE rstring length status call StatCheck address status return end G kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk C checks gpib status and prints error message subroutine StatCheck address status integer 2 address status if status ne 0 then write Error at device address status status endif return end SR620 Universal Time Interval Counter 52 Programming Examples Program Example 5 IBM PC Microsoft C v5 1 CEC GPIB Card This example illustrates binary transfer via the GPIB in C The file MS C488 h must be included in the source file and the program must be linked to the file GPIB L OBJ Both of these files are supplied by CEC Program to test TIC binary dump mode this program will binary dump samples from the time interval counter and convert the binary values to numbers in units appropriate to the measurement mode The program also demonstrates sending and receiving simple commands from the TIC The program uses the GPIB interface using an IBM PC with a Capital Equipment Co GPIB Interface card The necessary interface routines to this card are supplied by CEC and are linked to the program This program is written in Microsof
27. Terminate the A and B Performance Test 63 inputs in 50 ohms and set the trigger levels to 0 00V Set both A and B slopes to 4 Display the mean and verify that the reading is less than 1ns Record the reading 5 Display the jitter and verify that the reading is less than 50ps rms Record the reading Trigger Sensitivity These tests confirm that the A and B inputs and UHF prescalers have normal sensitivity 1 Attach the function generator s reference clock input to the SR620 s 10MHz output Set the function to square wave and the amplitude to 110mV pk pk with no offset 2 Connect the function generator to the SR620 s A input Terminate the input into 50 ohms set the trigger slope to and set the trigger level to 0 02 Volts this centers the hysteresis about 0 00V 3 Set the SR620 s mode to Frequency 1s gate 1 sample display to mean 4 Set the source to A the A trigger level to 0 02V and measure the frequency at the following frequencies 0 1 Hz 10Hz 1kHz 100kHz 1MHz and 10MHz note the 0 1 Hz measurement will take at least 40s to stabilize The frequencies should read setting Frequency Reading 0 1 Hz 0 1Hz 20 uHz 10 Hz 10 Hz 1 mHz 1 kHz 1 kHz 1 mHz 100 kHz 100 kHz 0 01Hz 1 MHz 1 MHz 0 1 Hz 10 MHz 10 MHz 1 0 Hz Record the results 5 Set the source to B the B trigger threshold to 0 02V terminate the B input into 50 Ohms set the trigger slope to connect the function g
28. The control menu allows the communications interfaces to be configured The GPIB address and RS 232 baud rates are set with this menu The first line of this menu will display the characters received from the controller in ASCII Hex The up down keys in the SCOPE AND CHART section may be used to scroll through the last 256 characters received A period after the right most digit indicates the last character received by the unit The RS 232 baud rate may be set from 300 to 19 2k baud If the RS 232 echo is enabled every character sent to the SR620 will be echoed back to the sender Use this only when using the SR620 with a dumb terminal DO NOT USE THE ECHO WHEN CONNECTED TO A COMPUTER EXCEPT WHEN RUNNING A TERMINAL EMULATION PROGRAM An RS 232 dwell delay is available to interface to slow computers Each unit of delay corresponds to about 2 ms of delay between characters Add delay if you experience problems when using the SR620 via the RS 232 Note The RS 232 characteristics set here will not affect the RS 232 port as used with a plotter The port will transmit at 9600 baud 8 data bits and no parity when used with a plotter Control Menu Items Line Default Display Comments 1 dAtA00000000 ASCII Hex of data from controller 2 AddrESS 16 GPIB Address 3 rS 232 bAud 9600 RS 232 baud rate 4 8232 Echo oFF Turn Echo ON if used with terminal Select 7 or 8 data bits per character Parity bit control sele
29. V stable dc power supply 5 10MHz frequency standard with better than 5 x 10 10 day aging such as a Cesium clock 6 180 degree rf power splitter with less than a few hundred picoseconds phase shift between the non inverting and inverting outputs such as Mini Circuits ZSCJ 2 1 7 2 equal less than 1 2 length BNC cables 8 BNC cable of known time delay Can be measured with SR620 Trigger Input Calibration Note This description refers to channel A Channels B and EXT have the same procedure Wherever a particular value is noted the values for B and EXT will be noted in parentheses B EXT Input Compensation 1 Connect the REF output to the A input with a coax cable Select TTL level for the REF OUT level Attach a compensated scope probe to R413 R443 R473 2 Adjust C402 C422 C442 for best pulse shape on the 10 us div scope display Input Threshold Offset Calibration 1 With the input open set the MODE to TIME and the arming EXT Turn off automeasure by pressing the RESET key in the SAMPLE SIZE section Select TRIG for the DISPLAY and set the TRIG threshold for O V 2 Set the slope to and calbyte 9 10 8 to 2200 3 Slowly reduce the value of calbyte 9 10 8 until the trigger light flashes This is the correct value 4 Set the slope to and calbyte 12 13 11 to 1800 5 Slowly increase the value of calbyte 12 13 11 until the trigger light flashes This is the correct value Input T
30. Z5U C 994 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 995 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 996 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 997 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U SR620 Universal Time Interval Counter 94 Parts List REF SRS PART VALUE C 998 5 00023 529 1U C 999 5 00023 529 1U C 1001 5 00125 520 12000U C 1002 5 00125 520 12000U C 1003 5 00169 520 4700U C 1004 5 00201 526 2200U C1005 5 00201 526 2200U C1006 5 00201 526 2200U C1007 5 00201 526 2200U C1008 5 00002 501 100P C1010 5 00023 529 1U C 1011 5 00023 529 1U C 1012 5 00023 529 1U C 1013 5 00023 529 1U C1014 5 00023 529 1U C1015 5 00023 529 1U C 1016 5 00023 529 1U C1017 5 00023 529 1U C1018 5 00023 529 1U C1019 5 00023 529 1U C1020 8 5 00023 529 1U C 1021 5 00023 529 1U C1022 5 00023 529 1U C 1023 5 00023 529 1U C1024 5 00023 529 1U C1025 5 00023 529 1U C1026 5 00197 501 18P C 1027 5 00197 501 18P C1028 5 00197 501 18P CU130 5 00022 501 001U D 101 3 00004 301 1N4148 D 102 3 00004 301 1N4148 D 103 3 00004 301 1N4148 D 121 3 00198 301 1N5231B D 122 3 00198 301 1N5231B D 123 3 00004 301 1N4148 D 124 3 00004 301 1N4148 D 125 3 00004 301 1N4148 D 126 3 00004 301 1N4148 D 127 3 00004 301 1N4148 D 201 3 00226 301 1N5822 D 251 3 00198 301 1N5231B D 252 3 00203 301 1N5711 D 302 3 00004 301 1N4148 D 303 3 00004 301 1N4148 D 402 3 00203 301
31. arming section will blink SR620 Universal Time Interval Counter Configuration Menus _ 17 CONFIGURATION MENUS The SR620 has many control parameters that are rarely if ever adjusted These parameters are set in the SR620 s four configuration menus The configuration menus are accessed by pressing either the SET or SEL keys in the CONFIG section of the front panel The submenu selection line then appears and one may choose the submenu of interest by pressing the SEL key The currently selected submenu name will flash Pressing the SET key will then scroll through the lines of the selected submenu Pressing the SEL key will return one to the submenu selection line The parameters displayed in each submenu line may be adjusted by pressing either the scale or the sample size up and down arrow keys The appropriate keys will always be under the parameter of interest Pressing any other keys will return one to the normal data display The four submenus are Configuration Menus ctrl Control GPIB and RS 232 data CAL Calibration data Clock source out Output graphs printer plotter DVM scales Jitter gate scale trigger scale Scn Scan menu points dwell D A and delay control Note The default parameter values for all settings will be recalled if the RESET button in the SAMPLE SIZE section is held down when the unit is turned ON This will also recall the factory calibration values CONTROL MENU ctrl
32. be in arming mode 6 7 or 8 AUTM 7 j The AUTM command sets the auto measurement mode The parameter j 1 sets the AUTO mode ON and the SR620 will automatically start a new measurement of N samples when the old one is complete The parameter j 0 sets the AUTO mode OFF and requires an individual command to start each measurement It is recommended that auto measurement be OFF if a computer is being used to take data as this allows SR620 Universal Time Interval Counter 32 Programming Commands synchronizing of the measurements with the returned answers DREL j The DREL command sets the display rel and is equivalent to the front panel SET REL button The parameter j 1 sets the REL j O clears the REL and j 2 clears the REL and the results of the last measurement j 3 sets the REL to the current cursor position COMP The COMP command changes the arming parity in time arming mode This command is the same as toggling the state of the front panel COMPL LED GATE x The GATE command sets the width of the frequency period or count gate to x The gate width x may range from ims to 500s in a 1 2 5 sequence If the value x is negative the gate is set to an externally triggered gate of width x If the measurement mode or arming mode do not support gates an error occurs JTTR j The JTTR command sets the type of jitter calculation The parameter j O sets standard deviation calculation while
33. gt or linefeed lt lf gt on RS232 or a linefeed lt lf gt or EOI on GPIB No command processing occurs until a command terminator is received All commands function identically on GPIB and RS232 Command mnemonics beginning with an asterisk are IEEE 488 2 1987 defined common commands These commands also function identically on RS232 Commands may require one or more parameters Multiple parameters are separated by commas Multiple commands may be sent on one command line by separating them by semicolons The difference between sending several commands on the same line and sending several independent commands is that when a command line is parsed and executed the entire line is executed before any other device action proceeds This allow SR620 Universal Time Interval Counter 30 Programming Commands synchronization to be achieved using the synchronization commands There is no need to wait between commands The SR620 has a 256 character input buffer and processes commands in the order received If the buffer fills up the SR620 will hold off handshaking on the GPIB and attempt to hold off handshaking on RS232 If the buffer overflows the buffer will be cleared and an error reported Similarly the SR620 has a 256 character output buffer to store output until the host computer is ready to receive it If the output buffer fills up it is cleared and an error reported The GPIB output buffer may be cleared by using the D
34. in effect until the front panel knob is rotated In remote mode the front panel knob is ignored If the trigger level is queried LEVL i the answer returned is a floating point number with 2 digits to the right of the decimal point for example 1 07 Programming Commands 31 MTRG j The MTRG command is equivalent to pushing the manual trigger button and only functions when the unit is in an external arming mode In the external gate modes the parameter j 1 starts the gate and j O stops the gate Otherwise the value of j is ignored The MTRG command has no effect if a measurement has not been started a STRT command or front panel button push or is the SR620 is in holdoff at the end of a scan point RLVL j The RLVL command sets the amplitude of the front panel reference output The parameter j O selects ECL output while j 1 selects TTL output TCPL i j The TCPL command sets the ac dc coupling of the channel A and B inputs The parameter j 0 selects dc while j 1 selects ac TERM i j The TERM command selects the input termination of the EXT A and B inputs The parameter j 0 selects 50 Ohm termination while j 1 selects 1 Mohm termination Also in frequency and period modes the value j 2 selects the UHF prescalers the 50 ohm terminator is automatically selected with the prescalers TMOD ij The TMOD command selects the trigger mode of the A and B inputs The parame
35. inputs Time intervals as a function of delay from an EXT trigger may be measured by using the internal delay generator The delay generator is triggered by the EXT input The trigger delay may be set or scanned via the CONFIG Menu Sample Arming___13 Time interval samples may also be armed by pressing the MAN key when in the EXT arming mode WIDTH Pulse widths may be measured in the WIDTH mode The pulse source may be either the A input the B input or the internal 1 kHz REF source The Start threshold and slope are set by the controls just above the A input The Stop threshold and slope are set by the controls just above the B input If the Start slope is positive the Stop slope will be negative and the time from a rising edge to a falling edge will be measured These controls are not used when measuring the width of the internal 1 KHz REF As pulse widths are always positive times only the TIME arming modes are available The three arming modes for WIDTH measurements are shown here The trigger source may be either the EXT input or the EXT triggered internally delayed scanned gate WIDTH Time Arming SIGNAL WIDTH Time External Arming SIGNAL WIDTH Time External Arming with Stop Hold Off SIGNAL GATE i RISE and FALL TIMES The transition time for an input may be measured in this mode Either the A or B input may be selected as the source to be measured The selected source is
36. j 1 sets Allan variance It should be noted that the jitter type is a property of the present mode and that if the mode is changed the jitter type may also change MODE j The MODE command sets the instrument measurement mode according to the following table j mode time width rise fall time frequency period phase count ouahon _o Note after setting the SR620 s mode the other measurement parameters should be set to their SR620 Universal Time Interval Counter desired values because changing modes may cause them to change SIZE x The SIZE command sets the number of samples in a measurement The parameter x may be between 1 and 1046 in a 1 2 5 sequence The SIZE query returns a floating point number with one significant digit SRCE j The SRCE command sets the source of the measurement The parameter j 0 set the source to A j 1 sets the source to B and j 2 sets the source to REF Additionally in frequency period and count modes j 3 sets the source to ratio A B In phase mode the source is fixed and may not be set while in rise fall time REF may not be selected as the source STRT The STRT command is equivalent to pushing the front panel START button STOP The STOP command resets the present measurement and is the same as pressing the RESET button on the front panel Data Transmission Commands MEAS j The MEAS query starts a measurement and returns the result w
37. l 65536 TEMP 5 J 760 NEXT J 770 if negative increment to get 2 s complement and change sign 780 IF SIGN lt gt 0 THEN FDATA I 1 FDATA I 1 790 multiply by conversion factor 800 FDATA l FACTORS TMODE 1 FDATA I 810 change scale if expand is on 820 IF TEXPD lt gt 0 THEN FDATA I FDATA I 001 830 NEXT 840 PRINT data 850 FOR I 1 TO SAMPLES 860 PRINT FDATA I 870 NEXT 880 GOTO 280 890 check for status error of last GPIB interraction 900 IF STATUS 0 THEN RETURN 910 PRINT gpib error status STATUS 920 STOP SR620 Universal Time Interval Counter 48 Programming Examples Program Example 4 IBM PC Microsoft Fortran v4 0 CEC GPIB Card This example illustrates the binary dump mode via the GPIB interface using Microsoft FORTRAN To use the CEC card with FORTRAN a file called FORT488 0BJ supplied by CEC is linked to the FORTRAN program Program to test TIC binary dump mode this program will binary dump samples from the time interval counter and convert the binary values to numbers in units appropriate to the measurement mode The program also demonstrates sending and receiving simple commands from the TIC The program uses the GPIB interface using an IBM PC with a Capital Equipment Co GPIB Interface card The necessary interface routines to this card are supplied by CEC and are linked to the program This program is written in Microsoft Fortran version 4 0 To co
38. mean and output 1 to be a programmable voltage source If j 3 both outputs are programmable sources Binary Dump Scale Factors DBEG j The DBEG command sets the start position of the internal delay scan The parameter j is the desired delay in units of number of gate widths The allowable range is between 1 and 50000 DSEN 2 j The DSEN command controls the enable status of the scanning delay The parameter j 0 sets the delay OFF If j 1 the delay is set to HOLD that is active but fixed in position If j 2 the delay is set to SCAN and will step by 1 step at the end of each group of samples Note that the SR620 MUST be in arming mode 6 7 or 8 for the delay scan to be functional and that an external trigger is required See the SCEN command DSTP 7 x The DSTP command sets the size of the scanning delay s step The range of sizes that may be set is between 1us and 10ms in a 1 2 5 sequence The DSTP query returns a floating point number with 1 significant digit HOLD 7 x The HOLD command sets the hold time at each scan point when in scan mode The hold time may range between 10ms and 1000s in 10ms increments The HOLD query return the hold time as a floating point number SCAN The SCAN command clears the current scan and starts a new scan The SCAN command automatically turns on the automeasure mode This command should not be used if one wants to manually control the acquisition of data during a
39. of between 1 and 50000 step sizes The delay will take one step after each scan point a maximum of 250 steps in a scan For arming modes that require a gate the delay will be followed by a gate of one step size width see ARMING section The delay enable may be set to off hold or scan In the off position the delay is disabled and the EXT input functions normally In the hold setting the delay is enabled but does not step This allows one to delay the EXT trigger by a known amount If one chooses hold and selects repeat scan the SR620 will function exactly as normal except for the delay between EXT and arming The scan setting will scan the delay by one step size after each scan point NOTE the arming mode must be set to EXT for the delay scan to function otherwise the delay scan is ignored If the delay scan is enabled the EXT led will blink The gate width and delay step size is set in the next line Gate widths from 1 us to 10 ms may be set in a 1 2 5 sequence The gate start position is set in the last line of the scan menu The start position may be set from 1 to 50 000 gate widths The gate delay will be increased by one gate width after each group of measurements per the SAMPLE SIZE EXAMPLE D A SCAN In this example the frequency of a VCO will be plotted as a function of applied voltage The VCO range is 1 to 6 VDC and we want at least 200 points in the scan The D A 2 output will be used to contro
40. proportional to the JITTER The scale factors for these outputs is the same as those set for the scope displays The default function may be overridden by selecting dAc instead of chrt allowing the D A voltage to be set and scanned The next menu allows the D A voltages to be set The up down keys may be used to adjust the voltages from 10 VDC in 5 mV steps If the source has been set to dAc and not chrt The D A will provide a voltage as set and the set voltage will be the starting point for each D A scan The step size taken by each D A may be programmed in the next line of this menu The step size may be adjusted to any value from 10 to 10 volts with 5 mV resolution For D A scans this is the last menu line which must be set If the step size is set for 0 0V the D A outputs will always be set to the programmed voltage However if the step size is not zero the D A voltages will only be reset when the scan is reset and the actual output voltage will be that corresponding to the current scan point Vout N step_size vstart SR620 Universal Time Interval Counter Line 7 is used to enable delay scans The SR620 s scanning delay is a programmable delay inserted between the EXT input and the sample arming circuitry These scans will of course require an external trigger and the arming mode to be set to EXT This delay may be adjusted in step sizes ranging from ims to 10ms with an initial delay at the beginning of the scan
41. scale 1 Attach the SR620 D A 0 output to DVM input 0 Attach the voltmeter so that it monitors the power supply voltage 2 Set the SR620 display to DVM 3 Set D A output 0 to 0 00 V Compare the SR620 reading to that of the voltmeter The difference should be lt 6mV Record the difference 4 Set D A output 0 to 1 80 V Compare the SR620 reading to that of the voltmeter The difference should be lt 6mV Record the difference Performance Test 65 5 Set D A output 0 to 10 00 V Compare the SR620 reading to that of the voltmeter The difference should be lt 60mV Record the difference 6 Repeat steps 1 5 for DVM input 1 Record the results THIS COMPLETES THE PERFORMANCE TESTS SR620 Universal Time Interval Counter 66 Performance Test SR620 Universal Time Interval Counter Performance Test 67 Serial Number Tested By Comments Functional Tests Display Test Self Test Ext Input A Input B Input Counter Tests Rear Panel Tests Performance Tests Timebase Frequency Accuracy Time Interval Accuracy Jitter Trigger Inputs A Comparators 0 1Hz 10Hz 1 kHz 100 kHz 1 MHz 10 MHz 100 MHz 300 MHz A UHF 300 MHz 1 3 GHz SR620 PERFORMANCE TEST RECORD Oscillator _________ Date Temperature Pass Fail Minimum Actual Maximum 9999999 9965 Hz 10000000 0035 Hz 1 ns 1 ns 0 50 ps 99 980 mHz 100 020 mHz 9 999 Hz 10 001 Hz 999 999 Hz 1000 001 Hz 99 99999 kHz 100 0
42. sets the DAC output scan start voltage The parameter j refers to the channel desired 0 or 1 and x is a voltage in the range 10 00 to 10 00 volts If the selected channel is not enabled to be a general purpose output this command has no effect If scans are disabled or the selected channel s voltage step size is set to O the output voltage is immediately set to x volts Otherwise the voltage is set to x at the beginning of the next scan VOUT j The VOUT query reads the present output voltage of the select d a channel This command can be used to monitor the stepping of the d a outputs during a scan VSTP j x The VSTP command sets the d a output scan step size The parameter j refers to the channel desired 0 or 1 and x is a voltage in the range 10 00 to 10 00 volts If the selected channel is not enabled to be a general purpose output this command has no effect The new step size becomes effective at the start of the next scan Graphics Control Commands AUTP 7 j The AUTP command sets the autoprint mode The parameter j 1 turns autoprint ON while j 0 turns autoprint OFF This command returns an error if the output device is set to plotter since autoprinting is not allowed with the plotter no time to change the paper AUTS The AUTS command autoscales the current graph It is the same as pushing the front panel autoscale button Note that autoscaling of the histogram is not completed until the NEX
43. size is equal to the gate width and the initial delay may be set between 1 and 50000 gates times This scanning ability allows one to make measurements of frequency as a function of time from some event such as the time response of a VCO to a step change in control voltage The RATIO of the frequencies of two inputs will be displayed if both the A amp B source LED are on It should be noted that the A and B frequencies are not measured simultaneously but are measured on alternate measurement cycles PERIOD Period measurements are done virtually the same way as frequency measurements however the reciprocal of the frequency is reported instead of the frequency Gating modes are identical to those used in the frequency mode When both the A and B source lights are on the ratio of the periods of signals applied to the A and B inputs may be displayed Period ratios may span from 10 9 to 10 3 PHASE The phase between the A and B inputs is measured in this mode of operation Two measurements are actually being done the period of the A input and the time interval between the A and B inputs For example suppose the A and B inputs are both 1 KHz square waves 1000us period with the rising edge of B coming 250us after the rising edge of A The unit would measure Sample Arming 15 the period of the A input Then it would make one measurement of the time interval between A and B The result 360 x 250us 1000us 90 0000 degrees
44. tests test the functionality of the SR620 from the front panel and verify the functionality of the circuitry The second set of tests actually measure the SR620 s specifications The results of each test may be recorded on the test sheet at the end of this section NECESSARY EQUIPMENT The following equipment is necessary to complete the tests The suggested equipment or its equivalent may be used 1 0 20 MHz synthesized function generator that can be phase locked to an external reference clock Such as Hewlett Packard HP3325B 2 100MHz 2 GHz synthesized signal generator such as Hewlett Packard HP8642B 2 Precision DC voltmeter such as Fluke 8840A 3 2 equal less than 1 2 length BNC cables 4 Epson compatible printer with PC compatible cable DB25 connector to Centronics connector 5 100MHZ or faster Oscilloscope 6 10MHz frequency reference such as a Cesium clock FUNCTIONAL TESTS These tests verify that the SR620 s circuitry is functional Front Panel Test This test verifies the functionality of the front panel digits LED s and buttons 1 Turn on the SR620 while holding down the DISP button A single segment of the leftmost digit should light Performance Test 61 2 Use the MODE up arrow key to light each segment 7 of them and the decimal point of the leftmost two digits Only a single segment should be on at a time The MODE down arrow key will step backward through the pattern 3
45. than it otherwise would in the absence of noise Because this is a random process this affects the resolution just as the other random noise sources do Trigger timing jitter can be minimized by careful grounding and shielding of the input and by maximizing the input slew rate Note however that the slew rate is limited by the SR620 s ns input rise time The trigger timing jitter can be described by the equation N E internal y EA Esrar Trigger Timing Jitter Input Slew Rate where E tema internal input noise 350 uV rms typical E pu gt input signal noise If the trigger level is set to a value other than the intended value the time interval measured will be in error This error trigger level timing error is a systematic error that affects only the error of the measurement and not its resolution The SR620 s trigger thresholds are set to an accuracy of 15mV 0 5 of value The effect this has on the measurement is given by 15mV 0 5 of setting Trigger Level Timing Error Input Slew Rate SR620 Universal Time Interval Counter 26 Specification Guide Graphs 3 and 4 show the effects of trigger timing jitter and trigger timing level error on resolution and error These graphs are applicable to all measurements not just time intervals rms Trigger Jitter vs Input Noise 10 Ea ae 100 ee 4 a a ee a Pa Ki 105 ge on PA ru E amp a i e e amp io slew rate 0 1 V us soe ae on A 2 E w Pa be Pai
46. the IEEE 488 1 1978 interface standard It also supports the required common commands of the IEEE 488 2 1987 standard Before attempting to communicate with the SR620 over the GPIB interface the SR620 s device address must be set The address is set in the CTRL submenu of the CONFIGuration menu and may be set between 0 and 30 Communicating with RS232 The SR620 is configured as a DCE transmit on pin 3 receive on pin 2 and supports CTS DTR hardware handshaking The CTS signal pin 5 is an output indicating that the SR620 is ready while the DTR signal pin 20 is an input that is used to control the SR620 s transmitting If desired the handshake pins may be ignored and a simple 3 wire interface pins 2 3 and 7 may be used The RS232 interface baud rate number of data bits and parity must be set These may be set in the CTRL submenu of the CONFIGuration menu The RS232 delay programs the time interval between the SR620 s transmitted characters if no handshaking is used The delay is equal to 2ms times the setting and is usually set to O no delay However some slower computers may require a delay The RS232 echo should be set OFF if the SR620 is connected to a computer It may be ON if connected to a terminal or a terminal emulation program RS232 echo and no echo operation When the RS232 echo mode is ON the SR620 will echo all characters sent to it will send linefeeds in addition to carriage returns and will return th
47. to the 16 digit LED display the SR620 s scope and chart outputs may be used to give the user alternative methods of viewing the data SCOPE OUTPUTS The SR620 may be attached to an oscilloscope operating in x y mode to provide a graphical presentation of the output data The oscilloscope should be set in x y mode with sensitivities set to 1V div and the SR620 s x and y rear panel outputs attached GRAPH TYPES The SR620 can then display either a histogram of number of samples vs measured parameter for the samples within a measurement a stripchart of mean values for successive measurements or a stripchart of jitter values for successive measurements In histogram mode a new graph will be displayed after each measurement of N samples is complete showing the distribution of samples in that measurement In the stripchart modes a new point will be added to the graph after each measurement indicating the mean and jitter values for that measurement The display desired is chosen by pressing the select button below the indicator LEDs The data for all three graphs are saved so that all of the graphs may be viewed by cycling through the three choices The data the scale values and the cursor position are all displayed on the scope screen In the stripchart modes up to 250 points will be displayed When the display fills up new data will start to overwrite the old starting from the left The graph may be cleared by pressing the CLR button be
48. to the D inputs of the start and stop latches The level at the D inputs is always high except in the Time arming mode The reset is set whenever the Load is asserted by the processor the reset may be extended beyond the end of Load in several ways For Time and Time arming internal arming Int_Arm is set low This will cause U506A Start_En to be set when the Load line goes low at the end of the reload cycle for the previous measurement removing the reset from the latch U604B which is holding the start latch U604A in reset U506B Stop_En is also set high when the load line goes low and so the line Start_En is set In the Time mode P_Time is low and so the reset to U608B which holds the stop latch in reset will not be removed until the start latch goes high in this way the stop latch is armed by the start pulse The Stop_Mpx output is delayed by 15 ns of coax cable to allow time for the stop latch s reset to be removed This allows time intervals from ns to 1000 s to be measured For TIME mode arming the Load pulse is extended if a start or stop pulse was not accompanied by a stop or start pulse while the unit was converting or reloading In this mode P M_Time is low removing the reset from the latches U612A amp B The flip flop U610A is a one bit counter of start pulses the U610B is a one bit counter of stop pulses The output of the XOR gates U611A amp C will be high if a start was not accom
49. to the bottom half of data memory is required The Z8800 has a prioritizing vector interrupt controller Hardware interrupts are assigned as follows Port Name Function P2_0 A D Int P2 2 Stop_Int P2_3 Gpib_Int P2 4 RTC A D conversion complete Stop received IEEE 488 interface 1 kHz real time clock P2_6 Ticks_6 To internal counter P3_2 Strt_Int Start received P3_4 Dropout Power supply dropout P3_6 Cycles_6 To internal counter The inputs to the internal 16 bit counters P2_6 and P3_6 will generate an interrupt on overilow These inputs will have a maximum frequency of about 1 5 MHz and so may generate interrupts at up to 60 Hz The other bits on the Z8800 s ports 2 amp 3 are used as follows Port Name Function P2_1 Busrq Requests assess to display RAM Printer strobe Reloads all counters and timers P3_0 RS232_In Received serial data P3_1 RS232_Out Transmitted serial data Busy Printer busy _5 DM Low for Data Memory P3_7 Ttlstopn Stop input enabled P2_5 Prnt Stb P2_7 Reload GPIB INTERFACE Sheet 2 of 16 The GPIB IEEE 488 interface is provided by U122 a TMS9914A controller U123 and U124 buffer data I O to the GPIB connector U122 is programmed to provide an Gpib_Int to the Z8800 when data is sent to the unit by the user s GPIB controller PRINTER INTERFACE Sheet 2 of 16 The instrument s firmware allows scope displays to be printed to Epson compatible printers Output
50. used as the input to both comparators The threshold knob above the A input is used to specify the Start voltage threshold and the knob above the B input is used to specify the Stop voltage threshold The rise time of the input is reported if positive slope is selected and the fall time is reported if negative slope is selected Either slope key changes both comparators slope LED s For example to measure the 20 80 rise time of a one volt input the A threshold would be set to 0 20 VDC the B threshold would be set to 0 80 VDC and the slope would be set to positive to measure the rising edge The 80 20 transition time of the falling edge could be measured by setting the slope to negative and adjusting the trigger thresholds Reported times are not corrected for the finite bandwidth of the input of the instrument The inputs have a bandwidth of about 300 MHz and so the 10 90 transition time of an infinitely fast input would be reported as 1 2 ns When measuring 10 90 transition times the actual transition time may be found by T actual S4 t T measured 1 2 ns2 As transition times are always positive numbers only TIME and TIME_EXT arming modes are allowed RISE FALL TIMES Time Arming SIGNAL RISE FALL TIMES External Arming SIGNAL SR620 Universal Time Interval Counter 14 Sample Arming FREQUENCY The frequency of either the A or B inputs may be measured in this mode of operation The SR620 is a
51. would be reported to the LED display Phase readings are always displayed between 180 and 180 degrees There are two gating options in phase mode INTERNAL and EXTERNAL In INTERNAL mode the gate for the period measurement is automatically set to 0 01s and the time interval measurement to time In EXTERNAL mode the gate time is determined by the width of a pulse applied to the EXT input Two pulses must be applied to the EXT input for each complete measurement the first arms the time interval measurement and the second gates the period measurement The external arming pulses must be separated by at least 15 ms Additionally one may use the EXT input to trigger the 1us to 10ms scannable gates in order to measure phase as a function of time for repetitive events COUNT In this mode the unit will display the number of events at the A or B inputs which occurred during the gate The gate choices are the same as for frequency and period modes As in the frequency mode of operation an internal gate may be triggered by or delayed relative to the EXT input An event occurs when the input passes through threshold with the selected slope When both the A and B source LED s are on the ratio A B of events occurring on the two channels is displayed N cycles At DELAYED ARMING MODES In addition to the externally triggered arming modes discussed previously the SR620 has a method of delayed external arming in which a user adju
52. 0 34 ZO 7 00166 720 SR620 36 Main Board Parts List REF SRS PART VALUE BT101 6 00001 612 BR 2 3A 2PIN PC C1 5 00023 529 1U C1A 5 00272 532 39P C2 5 00023 529 1U C2A 5 00328 529 3 3P C3 5 00002 501 100P C3A 5 00272 532 39P C 4 5 00002 501 100P C4A 5 00023 529 1U C 101 5 00008 501 22P C 102 5 00008 501 22P C 103 5 00008 501 22P C 104 5 00008 501 22P C 105 5 00052 512 01U C 106 5 00021 501 82P Parts List 89 DESCRIPTION Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg nn pia aili iea nj a Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Cable Coax amp Misc Wire 24 UL1007 Strip 1 4x1 4 Tin Wire 24 UL1007 Strip 1 4x1 4 Tin Grommet Screw Sheet Metal Washer nylon Screw Panhead Phillips Power Button Wire 22 UL1007 Wire 22 UL1007 Wire 22 UL1007 Wire 22 UL1007 Termination Cable Assembly Ribbon Connector Male Ferrite Beads Keypad Conductive Rubber Fabricated Part Fabricated Part DESCRIPTION Battery Cap Monolythic Ceramic 50V 20 Z5U Capacitor Ceramic Disc 50V 10 NPO Cap Monolythic Ceram
53. 0001 kHz 999 9999 kHz 1 0000001 MHz 9 999999 MHz 10 000001 MHz 99 99999 MHz 100 00001 MHz 299 99997 MHz 300 00003 MHz 299 99997 MHz 300 00003 MHz 1 29999987 GHz 1 30000013 GHz SR620 Universal Time Interval Counter 68 Performance Test Minimum Actual Maximum B Comparators 0 1Hz 99 980 mHz 100 020 mHz 10Hz 9 999 Hz 10 001 Hz 1 kHz 999 999 Hz 1000 001 Hz 100 kHz 99 99999 kHz 100 00001 kHz 1 MHz 999 9999 kHz 1 0000001 MHz 10 MHz 9 999999 MHz 10 000001 MHz 100 MHz 99 99999 MHz 100 00001 MHz 300 MHz 299 99997 MHz 300 00003 MHz B UHF 300 MHz 299 99997 MHz 300 00003 MHz 1 3 GHz 1 29999987 GHz 1 30000013 GHz Trigger Accuracy A OV 0 015 V 0 015 V A 4V 3 965 V 4 035V B OV 0 015 V 0 015 V B 4V 3 965 V 4 035V D A Accuracy D A 0 10 0V 9 97 V 10 03 V D A 0 0 0V 0 03 V 0 03 V D A 0 10 0V 9 97 V 10 03 V D A 1 10 0V 9 97 V 10 03 V D A 1 0 0V 0 03 V 0 03 V D A 1 10 0V 9 97 V 10 035 V DVM Accuracy DVM 0 0 0V A 0 006V A 0 006V DVM 0 1 8V A 0 006V A 0 006V DVM 0 10 0 V A 0 06V A 0 06V DVM 1 0 0V A 0 006V A 0 006V DVM 1 1 8V A 0 006V A 0 006V DVM 1 10 0 V A 0 06V A 0 06V SR620 Universal Time Interval Counter CALIBRATION The SR620 is calibrated by adjusting calibration constants which are stored in the units battery backed up RAM The calibration values which were determined when the unit was manufactured are stored in the unit s ROM and may be recalled at any time
54. 0062 513 0022U C 447 5 00049 566 001U C 448 5 00003 501 10P C 449 5 00023 529 1U C 450 5 00023 529 1U C 451 5 00023 529 1U C 452 5 00023 529 1U C 453 5 00141 503 22U C 454 5 00092 523 1P C 455 5 00092 523 1P C 456 5 00092 523 1P C 461 5 00002 501 100P C 495 5 00023 529 1U C 496 5 00023 529 1U C 497 5 00023 529 1U C 498 5 00023 529 1U C 499 5 00023 529 1U C 500 5 00008 501 22P C 600 5 00159 501 6 8P C 701 5 00134 529 100P C 702 5 00023 529 1U C 703 5 00002 501 100P C 704 5 00023 529 1U C 705 5 00049 566 001U Parts List 91 DESCRIPTION Cap Polyester Film 50V 5 40 85c Rad Capacitor Ceramic Disc 50V 10 SL Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Ceramic Disc 50V 20 Z5U Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Variable Misc Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Ceramic Disc 50V 10 SL Capacitor Mylar Poly 50V 5 Rad Cap Polyester Film 50V 5 40 85c Rad Capacitor Ceramic Disc 50V 10 SL Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Ceramic
55. 05 U 604 3 00194 340 MC10H131 U 605 3 00194 340 MC10H131 U 607 3 00201 340 MC10H105 U 608 3 00194 340 MC10H131 U 609 3 00194 340 MC10H131 U 610 3 00194 340 MC10H131 U 611 3 00213 340 MC10H113 U 612 3 00194 340 MC10H131 U 701 3 00093 340 LM13600 U 702 3 00065 340 CA3102 U 703 3 00087 340 LF347 U 704 3 00199 340 74HC4538 U 705 3 00076 340 DG211 U 706 3 00087 340 LF347 U 707 3 00151 340 MC10125 U 801 3 00087 340 LF347 U 802 3 00076 340 DG211 U 803 3 00270 340 74HC4051 U 805 3 00271 340 AD7578KN U 806 3 00059 340 7542 U 807 3 00087 340 LF347 U 808 3 00270 340 74HC4051 U 809 3 00088 340 LF353 U 810 3 00088 340 LF353 U 901 3 00143 340 LM393 DESCRIPTION Integrated Circuit Thru hole Pkg Relay Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Relay Integrated Circuit Thru hole Pkg Relay Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Ci
56. 0X4 N 340 4 00463 421 82X4 N 401 4 00564 421 3 3KX3 N 402 4 00564 421 3 3KX3 N 403 4 00564 421 3 3KX3 N 404 4 00423 421 150X3 N 405 4 00423 421 150X3 N 406 4 00423 421 150X3 N 407 4 00573 425 47X7 N 408 4 00262 425 100X7 N 409 4 00284 421 1 0KX4 N 451 4 00254 421 1 0KX3 N 452 4 00491 421 27KX3 N 453 4 00334 425 10KX5 N 501 4 00262 425 100X7 N 502 4 00262 425 100X7 N 503 4 00262 425 100X7 N 504 4 00262 425 100X7 N 505 4 00247 425 100X9 N 506 4 00262 425 100X7 N 507 4 00262 425 100X7 N 509 4 00463 421 82X4 N 551 4 00463 421 82X4 N 650 4 00262 425 100X7 N 651 4 00298 425 470X5 N 652 4 00262 425 100X7 N 653 4 00298 425 470X5 N 654 4 00262 425 100X7 N 655 4 00262 425 100X7 N 666 4 00262 425 100X7 N 667 4 00262 425 100X7 N 701 4 00337 421 47X5 N 702 4 00297 421 100KX5 N 711 4 00337 421 47X5 N 712 4 00297 421 100KX5 N 771 4 00463 421 82X4 N 801 4 00438 421 22KX4 N 802 4 00258 421 100KX4 N 803 4 00284 421 1 0KX4 N 804 4 00220 420 10KX8 PC1 7 00700 701 TCXO BOARD PC101 7 00173 701 SR620 Q 101 3 00140 325 2N2369A SR620 Universal Time Interval Counter DESCRIPTION Res Network SIP 1 4W 2 Isolated Res Network SIP 1 4W 2 Isolated Res Network SIP 1 4W 2 Isolated Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Res Network SIP 1 4W 2 Isolated Res Network SIP 1 4W 2 Isolated Res Network SIP 1 4W 2 Isolate
57. 1 999 or 19 99 VDC Sample amp hold with successive approximation converter 1 M Ohm 0 3 of full scale Formatted response in approximately 5 ms Two rear panel outputs which may be ramped 10 00 VDC 5 mV lt 1 Ohm SR620 Universal Time Interval Counter Specifications _ix Default Voltage proportional to Mean amp Deviation Accuracy 0 3 of full scale Graphics Live scope displays and hardcopy Scope Two rear panel outputs to drive x y scope Displays Histograms and strip charts of mean amp deviation X axis 5 to 5 V for 10 division deflection Y axis 4 to 4 V for 8 division deflection Resolution 250 H x 200 V pixels Hardcopy Via Centronics port to Epson graphics compatible dot matrix printers RS 232 IEEE 488 to HP GL compatible Digital Plotters Interfaces RS 232C 300 to 19 2 KBaud All instrument functions may be controlled PC compatible serial cable GPIB IEEE 488 compatible interface All instrument functions may be controlled Speed Approximately 150 ASCII formatted responses per second 1400 binary responses per second General Operating 0 to 50 C Power 100 120 220 or 240 VAC 5 10 50 60 Hz 70 Watts Dimensions 14 x 14 x 3 5 Rack mounting hardware included Weight 11 Ibs Comparator Sensitivity V rms Comparator Sensitivity vs Frequency Prescaler Sensitivity vs Frequency ty Specification Limit Prescaler Sensitivity V rms e Typical A Fe II EEE SIR OR
58. 1 format 11 A 11 C convert data and print both binary and converted form call Convert tmode texpd samples data fdata write write data do 20 i 0 samples 1 write 102 data 4 i 3 data 4 i 2 data 4 i 1 data 4 i fdata i 20 continue 102 format 1X 4Z4 converted D22 15 goto 10 11 continue end C kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk C converts the binary data to real numbers subroutine Convert tmode texpd samples data fdata integer 2 tmode texpd samples data 0 19999 sign integer 4 words 0 4 real 8 fdata 0 4999 real 8 factors 0 6 C conversion factors data factors 1 05963812934D 14 1 05963812934D 14 1 05963812934D 14 1 24900090270331D 9 1 05963812934D 14 8 3819032D 8 00390625 do 10 i 0 samples 1 sign 0 fdata i 0 0DO C get 8 data bytes do 11 j 0 3 words j data 4 i j C get unsigned magnitude of word if words j It 0 words j 65536 words j 11 continue C if answer less than 0 change sign and get magnitude if data 4 i 3 It 0 then sign 1 do 12j 0 3 C take 1 s complement of number SR620 Universal Time Interval Counter 50 Programming Examples words j 65535 words j 12 continue endif C convert to floating point do 13 j 0 3 fdata i fdata i 65536 0D0 words 3 j 13 continue C if number is negative add 1 to get 2 s complement and change sign if sign eq 1 fdata i 1 0D0 fdata i 1 0D0 C multipl
59. 10KX3 DESCRIPTION Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Varistor Zinc Oxide Nonlinear Resistor Cable Coax amp Misc Cable Coax amp Misc Cable Coax amp Misc Cable Coax amp Misc Connector BNC Connector BNC Connector IEEE488 Reverse R A Female Connector D Sub Right Angle PC Female Connector D Sub Right Angle PC Female Connector Male Connector BNC Connector BNC Connector BNC Connector BNC Connector BNC Connector BNC Inductor Axial Inductor Radial Inductor Inductor Inductor Axial Inductor Inductor Inductor Axial Inductor Vertical Mount Resistor Network SIP 1 4W 2 Common Res Network SIP 1 4W 2 Isolated Resistor Network SIP 1 4W 2 Common Resistor Network DIP 1 4W 2 8 Ind Resistor Network DIP 1 4W 2 8 Ind Resistor Network DIP 1 4W 2 8 Ind Resistor Network DIP 1 4W 2 8 Ind Resistor Network DIP 1 4W 2 8 Ind Res Network SIP 1 4W 2 Isolated Res Network SIP 1 4W 2 Isolated SR620 Universal Time Interval Counter 96 Parts List REF SRS PART VALUE N 250 4 00460 421 33X4 N 251 4 00248 421 150X4 N 252 4 00248 421 150X4 N 303 4 00262 425 100X7 N 308 4 00247 425 100X9 N 309 4 00262 425 100X7 N 310 4 00293 421 470X4 N 311 4 00245 421 4 7KX4 N311A 4 00265 421 10
60. 1s to 1000 s in 01 s steps Clears and restarts a scan Enables scanning O disabled 1 single scan mode 2 repeat scan mode Clears the scan Returns the number of the last completed scan point Returns 0 if no points are complete Sets number of scan points to 2 5 10 25 50 125 250 Sets the DAC output scan starting voltage If scans are disabled or the step size is zero the output is immediately set to the new voltage Otherwise the voltage is updated at the start of the next scan Reads the current output voltage of DAC channel j Sets the DAC scan step size to x volts Sets the autoprint mode to 0 off or 1 on Autoscales the displayed graph Sets the cursor position to j Sets the displayed graph to 0 histogram 1 mean 2 jitter Clears the displayed graph SR620 Universal Time Interval Counter Abridged Command List _ xiii GENA j GSCL j x PDEV j PLAD j PLPT j PLOT PCLR Front Panel Control DISP j EXPD j KEYS j Rear Panel Control CLCK j CLKF j Interface Control Commands RST IDN OPC WAI ENDT j k I m LOCL j WAIT j Status Reporting Commands CLS ESE j ESR j PSC 2 j SRE j STB j EREN j ERRS j STAT j TENA j STUP Calibration Control TAC j PHK j Turns graphs 0 off 1 on Sets the graph scales j O histogram verticalscale j 1 histo horizontal j 2 histo bins j 3 mean graph scale j
61. 2 watt resistor so the average voltage should not exceed 5 Vdc U407 detects the voltage at the input if it exceeds 5 Vdc or if the RF buffered by the emitter follower Q404 and detected by D403 exceeds 5 Vdc then the OVLD_A bit is asserted This bit is polled by the processor which opens relay if an overload is detected The firmware will then blink the 50 Ohm LED to inform the user that the termination has been removed When the input is terminated into 50 Ohms the input signal is ac coupled to the prescaler U403 The prescaler has a 10 mV rms sensitivity and can provide a divide by 64 output for inputs up to 1 3 GHz The input to the prescaler is limited to the bias currents in Q404 and D402 Large positive excursions will reverse bias D402 and large negative excursions will turn off Q404 The prescaler is powered by Q405 if Pre_A_En is low This prevents outputs from the prescaler from interfering in measurements when it is not needed The output from the prescaler is shifted to ECL levels by the emitter follower on its output The input signal is attenuated by R403 and R404 and compensated by C402 C402 is adjusted for good pulse response by viewing a step input at the emitter of Q403 on 10 us div The attenuated input signal is limited by D404 405 and buffered by Q401 a fast n channel JFET and by the emitter follower Q403 The op amp U404 adjusts the drain current in Q401 so as to maintain dc accuracy across the Q401
62. 20 s timebase short term stability is specified by its Allan variance Specified values for 1 second gate times are standard oscillator oven oscillator 1 0s gate 3x10 10 5x10 12 The resolution of the SR620 is specified as resolution 25ps 2 time interval x short term stability 2 1 2 rms so for time interval greater than 125ms standard oscillator or 500ms oven oscillator the short term stability of the timebase will dominate the resolution limit of the SR620 LONG TERM STABILITY The long term stability of an oscillator is a measure of its changes in frequency over long time intervals hours days months or years It is the long term stability of the timebase that will ultimately limit the absolute SR620 Universal Time Interval Counter Specification Guide ___ 25 accuracy of the SR620 and determines the calibration interval necessary to maintain a desired error limit The long term stability consists of two components oscillator aging and oscillator temperature response The aging of an oscillator is the change in frequency over time due to physical changes in the components usually the crystal and is usually specified as a fractional frequency change over some measurement period Temperature response is due to changes in the oscillator characteristics as a function of ambient temperature and is specified as a fractional frequency change over some temperature range The timebase for the SR620 is specified as standard oscill
63. 3 4 00061 401 240K SR620 Universal Time Interval Counter DESCRIPTION Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Wire Wound Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Thermistor various Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Wire Wound Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50P
64. 4 ZO 0 00017 002 TRANSCOVER ZO 0 00025 005 3 8 ZO 0 00042 010 4 40 HEX ZO 0 00048 011 6 32 KEP ZO 0 00079 031 4 40X3 16 M F Zo 0 00089 033 4 ZO 0 00096 041 4 SPLIT ZO 0 00109 050 1 1 2 18 Z0 0 00113 053 10 24 ZO 0 00122 053 2 1 4 24 ZO 0 00126 053 3 1 2 24 ZO 0 00133 052 7 1 2 22 ZO 0 00134 053 7 1 4 24 ZO 0 00136 053 8 1 2 24 ZO 0 00153 057 GROMMET2 ZO 0 00158 070 60MM 24V ZO 0 00165 003 TO 18 ZO 0 00181 020 6 32X1 4PF ZO 0 00186 021 6 32X1 3 8PP ZO 0 00209 021 4 40X3 8PP ZO 0 00211 020 4 40X5 8PF ZO 0 00231 043 1 32 4 SHOULD ZO 0 00240 026 4 40X3 8PF ZO 0 00243 003 TO 220 ZO 0 00253 044 SR620 ZO 0 00256 043 6 SHOULDER ZO 0 00263 052 3 22 ZO 0 00264 052 9 1 2 22 RD ZO 0 00265 052 9 1 2 22 BLK ZO 0 00266 052 8 1 2 22 BLK ZO 0 00292 026 6 32X3 16 TRUSS ZO 0 00407 032 SOLDR SLV RG174 ZO 0 00500 000 554808 1 ZO 0 00514 030 TUBULAR NYLON ZO 0 00520 048 18 18 Zo 0 00522 053 3 1 2 24 Zo 1 00066 112 7 PIN 24AWG WH SR620 Universal Time Interval Counter DESCRIPTION Integrated Circuit Integrated Circuit Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Voltage Reg TO 220 TAB Package Voltage Reg TO 220 TAB Package Voltage Reg TO 220 TAB Package Integrated Circuit Thru hole Pkg Crystal Crystal Crystal Crystal Power Entry Hardware Power Entry Hardware Lugs Nut Hex Nut Kep Standoff Tie
65. 4 jitter graph scale x units per division or bins Sets output device to 0 printer 1 plotter Sets the plotter GPIB address Sets the plotter port to O RS232 1 GPIB Initiates a print plot Clears plots prints Sets the display source 0 MEAN 1 REL 2 JITTER 3 MAX 4 MIN 5 TRIG 6 DVM s Set the x1000 expand status in freq and per mode 0 off 1 on Simulates a keypress or reads the most recently pressed key Sets the clock source 0 internal 1 external Sets the external clock frequency 0 10MHz 1 5MHz Sets reads the binary I O port when enabled Sets the printer port mode 0 print 1 input 2 output Sets the full scale voltage of DVM input i Reads DVM channel 0 or 1 Clears instrument to default settings Returns the device identification Operation complete common synchronization command Either sets a status bit or returns a value when all operations scans prints measurements are complete Wait synchronization command Holds off further command execution until all in progress operations scans prints measurements are complete Sets the RS232 end transmission terminator Sets the RS232 local remote function O local 1 remote 2 local lockout Sets the RS232 intercharacter time delay Clears all status registers Sets reads the standard status byte enable register Reads the standard status register or just bit j of register Sets the power on status clear bit This allows SRQ so
66. 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 968 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 969 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 970 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 971 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 972 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 973 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 974 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 975 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 976 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 977 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 980 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 981 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 982 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 983 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 984 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 985 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 986 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 987 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 988 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 990 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 991 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 992 5 00023 529 1U Cap Monolythic Ceramic 50V 20 Z5U C 993 5 00023 529 1U Cap Monolythic Ceramic 50V 20
67. 6 Transistor TO 92 Package Q 406 3 00021 325 2N3904 Transistor TO 92 Package Q 411 3 00030 325 J310 Transistor TO 92 Package Q 412 3 00021 325 2N3904 Transistor TO 92 Package Q 413 3 00018 324 MRF904 Transistor TO 72 Package Q 421 3 00030 325 J310 Transistor TO 92 Package Q 422 3 00021 325 2N3904 Transistor TO 92 Package Q 423 3 00018 324 MRF904 Transistor TO 72 Package Q 424 3 00018 324 MRF904 Transistor TO 72 Package Q 425 3 00022 325 2N3906 Transistor TO 92 Package Q 426 3 00021 325 2N3904 Transistor TO 92 Package Q701 3 00022 325 2N3906 Transistor TO 92 Package Q 702 3 00022 325 2N3906 Transistor TO 92 Package Q 711 3 00022 325 2N3906 Transistor TO 92 Package Q 712 3 00022 325 2N3906 Transistor TO 92 Package Q 801 3 00027 325 2N5770 Transistor TO 92 Package Q 802 3 00028 325 2N5771 Transistor TO 92 Package Q 803 3 00027 325 2N5770 Transistor TO 92 Package Q 804 3 00028 325 2N5771 Transistor TO 92 Package Q 901 3 00257 329 TIP41B Voltage Reg TO 220 TAB Package Q 902 3 00177 321 2N2222 Transistor TO 18 Package Q 903 3 00258 329 TIP42 Voltage Reg TO 220 TAB Package Q 904 3 00022 325 2N3906 Transistor TO 92 Package Q 905 3 00258 329 TIP42 Voltage Reg TO 220 TAB Package Q 906 3 00022 325 2N3906 Transistor TO 92 Package Q 907 3 00022 325 2N3906 Transistor TO 92 Package Q 908 3 00257 329 TIP41B Voltage Reg TO 220 TAB Package SR620 Universal Time Interval Counter 98 Parts List REF SRS PART VALUE
68. 73 120 INSL Connector BNC J 402 1 00073 120 INSL Connector BNC J 403 1 00073 120 INSL Connector BNC P 1 4 00445 447 SR620 48 Pot Single Control P2 4 00445 447 SR620 48 Pot Single Control P3 4 00445 447 SR620 48 Pot Single Control PC1 7 00155 701 SR620 19 Printed Circuit Board SW901 2 00023 218 DPDT Switch Panel Mount Power Rocker SW902 0 00443 000 SWITCH Hardware Misc U 1 3 00288 340 HDSP H101 Integrated Circuit Thru hole Pkg U2 3 00288 340 HDSP H101 Integrated Circuit Thru hole Pkg U3 3 00288 340 HDSP H101 Integrated Circuit Thru hole Pkg SR620 Universal Time Interval Counter REF SRS PART VALUE U 4 3 00288 340 HDSP H101 U5 3 00288 340 HDSP H101 U 6 3 00288 340 HDSP H101 U 7 3 00288 340 HDSP H101 U8 3 00288 340 HDSP H101 U9 3 00288 340 HDSP H101 U 10 3 00288 340 HDSP H101 U 11 3 00288 340 HDSP H101 U 12 3 00288 340 HDSP H101 U 13 3 00288 340 HDSP H101 U 14 3 00288 340 HDSP H101 U 15 3 00288 340 HDSP H101 U 16 3 00288 340 HDSP H101 ZO 0 00051 056 RG174 ZO 0 00112 053 1 3 4 424R ZO 0 00132 053 6 1 2 24 ZO 0 00153 057 GROMMET2 ZO 0 00172 027 44X1 4PPA ZO 0 00183 043 10 SHOULDER Zo 0 00209 021 4 40X3 8PP Zo 0 00237 016 F1404 Zo 0 00267 052 6 1 2 22 RED Zo 0 00268 052 6 1 2 22 BL Zo 0 00269 052 7 75 WHITE Z0 0 00270 052 7 3 4 22 BLUE ZO 0 00407 032 SOLDR SLV RG174 ZO 1 00052 171 40 COND Zo 1 00088 130 40 PIN DI Zo 6 00213 630 2 HOLE Zo 7 00156 740 SR620 28 ZO 7 00161 720 SR62
69. CE select positive slope for START and STOP and set B s threshold pot for AUTOLEVEL EXCESSIVE JITTER The most common causes of excess jitter are 1 incorrect trigger thresholds 2 noise or amplitude fluctuations on the input signals 3 insufficient or excessive amplitude on the inputs slow input signal slew rates 5 improper slope selection check the MEAN value to be certain that you are measuring the correct time interval 6 improperly terminated inputs SR620 Universal Time Interval Counter SCOPE DISPLAY PROBLEMS Scope display problems are usually due to the set up of the X Y scope Make certain that the scope is in the XY mode with 1V div terminated into 1M Ohm The XY mode is sometimes difficult to setup some scopes have multiple controls which must be in the correct position to operate in the XY mode Please refer to your scope s operation manual A jumping or distorted display will result if the scope is ac coupled If the scope has cursor read outs turn these read outs off to avoid a blinking display A poorly compensated scope input will cause minor distortion of the display PRINTER and PLOTTER PROBLEMS The printer must be connected to the PRINTER PORT on the back panel Plotters may be connected to either the RS 232 or the GPIB port You must set parameters in the OUTput menu in the CONFIG section to specify whether you are using the printer or a plotter If you specify a plotter you need to spe
70. Cmp3 is set high For delayed gates the programming of the 8254 s is quite different In this case the period of the output of the 2 3 of the 8254 is set to the gate width and the 3 3 of the 8254 is programmed to go low for one clock cycle after counting down the delay Of course the programmed delay must be some integer number of gate widths The firmware supports gate widths and delay resolution from 1 us to 10 ms in a 1 2 5 sequence TIMEBASE Sheet 7 of 16 The standard timebase is U1A a 10 00000 MHz 1 ppm TCXO with aging characteristics of about 1 ppm yr U1A is powered by U301 which re regulates 15 VDC to 5 VDC U1A provides a 10 MHz sine output The optional timebase is U303 an ovenized 10 MHz crystal oscillator with 5x10 10 day aging and 2x10 9 stability over O to 50 C This oscillator also provides a sine wave output which is selected by the jumper SW301 When the optional oscillator is used U301 regulates 15 VDC to 12 VDC The selected timebase is ac coupled into and buffered by the emitter follower Q306 which is coupled to the rear panel output via the 10 MHz tank C324 and L305 This output provides a clean 10 MHz 1 Vrms sinewave into a 50 Ohm load The emitter follower Q307 buffers the 10 MHz sine wave into U304 an ECL differential line receiver configured as a Schmitt trigger The harmonic generator U314B creates a train of pulses which are 5 ns wide with a pulse repetition rate of 10 MHz T
71. Counter 28 Specification Guide PHASE MODE In phase mode the measurement resolution and error are given by N number of samples averaged note the gate time is 10ms in internal mode Resolution 0 001 360 25ps gate time x short term stability 2 x rigger jitter phase x period vA period x N 360 x gate time timebase error x timeinterval start trigger level error stop trigger level error 0 5ns Error resolution A x 360 timebase error x period 1x 10 x period Graph 6 shows the SR620 s single shot phase resolution as a function of frequency The resolution may be increased by averaging Single Shot Phase Resolution vs Frequency Phase Resolution deg 1 rara 105 104 10 10 107 wE Frequency Hz Graph 6 Single Shot phase resolution vs frequency COUNT MODE The resolution and error for count mode are Resolution 1 count Error 1 count SR620 Universal Time Interval Counter Programming Commands 29 PROGRAMMING THE SR620 The SR620 Universal Time Interval Counter may be remotely programmed via either the RS232 or GPIB IEEE 488 interfaces Any computer supporting one of these interfaces may be used to program the SR620 Both interfaces are active at all times the SR620 will send responses to the interface which asked the question All front and rear panel features except power may be controlled Communicating with GPIB The SR620 supports
72. DESCRIPTION PROCESSOR SYSTEM Sheet 1 of 16 The processor is a Z8800 Super 8 which integrates a fast 8 bit microprocessor UART counter timers and an interrupt controller into one VLSI component The processor is clocked at just above 20 MHz The crystal X101 is specified as a series resonant 20 MHz crystal so it will oscillate at a few kiloHertz above 20 MHz with the parallel 30 pF load This crystal is used only for processor timing The processor can address 128K of memory There are 16 address bits and one bank select bit The bank select bit DM is low to select data memory and high to select program memory The lower 8 bits of the address bus are latched off the data bus by U102 The firmware and the factory calibration bytes reside in U103 a 64Kx8 200 ns UVEPROM which occupies all of program memory U104 is a 32Kx8 static RAM whose contents are preserved on power down by the lithium battery The chip select to the RAM is inhibited when the RESET is asserted by Q101 This prevents corruption of the RAM contents when the power is turned off This static RAM is mapped into the top half of data memory Port strobes are generated by U106 and U107 I O ports are mapped into the bottom 1 4 of data memory while the 8Kx8 display memory is mapped into the 2 4 of the bank Various control signals are generated by U108 110 The buffered data bus to all of the system s I O ports is enabled only if access
73. Disc 50V 20 Z5U Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Cap Monolythic Ceramic 50V 20 Z5U Capacitor Variable Misc Capacitor Mylar Poly 50V 5 Rad Cap Polyester Film 50V 5 40 85c Rad Capacitor Ceramic Disc 50V 10 SL Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Ceramic Disc 50V 20 Z5U Capacitor Silver Mica Miniature Capacitor Silver Mica Miniature Capacitor Silver Mica Miniature Capacitor Ceramic Disc 50V 10 SL Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Ceramic Disc 50V 10 SL Cap Monolythic Ceramic 50V 20 Z5U Cap Polyester Film 50V 5 40 85c Rad SR620 Universal Time Interval Counter 92 Parts List REF SRS PART VALUE C 706 5 00136 519 01U C 711 5 00134 529 100P C 712 5 00023 529 1U C 713 5 00002 501 100P C 714 5 00023 529 1U C 715 5 00049 566 001U C 716 5 00136 519 01U C 801 5 00023 529 1U C 802 5 00023 529 1U C 803 5 00023 529 1U C 804 5 00023 529 1U C 805 5 00136 519 01U C 806 5
74. END CONTROL BITS Sheet 5 of 16 U234 and the associated emitter followers Q210 212 and U239 are used to control front end relays These relays select signal sources for the comparators select ac or dc coupling and control the 50 Ohm terminators The definitions of these control bits is given in the table here Bit Name Function O A_50 Low for 50 Ohm on A 1 B_50 Low for 50 Ohm on B 2 Ext_50 Low for 50 Ohm on Ext 3 A de Low for dc couple on A 4 B_dc Low for dc couple on B 5 CMP1_A B Selects A or B for Comp1 6 CMP2_B A_ Selects B or A for Comp2 7 CMP3_E C Selects Ext or Int Cal for Comp3 ADC DAC and MISC CONTROL BITS Sheet 5 of 16 U235 controls the analog to digital converter ADC multiplexer and digital volt meter DVM source and gain See sheet 12 of 16 The table below defines each bit it Name Function O Adc_Mpx0 LSB of ADC multiplexer 1 Adc_Mpx1 Middle bit of ADC multiplexer 2 Adc_Mpx2 MSB of ADC multiplexer 3 Adc_S H Low to sample DVM input 4 Adc_Gain Low for 2 VFS high for 20 VFS 5 Adc High to select DVM1 6 Adci Low to select DVM1 7 Int Gaten High for internal gate enable There are eight digitally controlled analog voltages used in the instrument These voltages are supplied by one 12 bit digital to analog converter DAC which refreshes eight sample and hold amplifiers See sheet 12 of 16 U236 controls the DAC multiplexer and provides four other miscellaneous bits The defi
75. ET key to terminate the present measurement Press and hold the RESET key to turn the AUTO LED and automeasure off SR620 Universal Time Interval Counter 4 Front Panel Operation width rise fall time frequency period phase count NOTES SUMMARY OF ARMING MODES arming mode TIME TIME EXTERNAL TIME EXTERNAL STOP HOLDOFF TIME TIME COMPLEMENT TIME EXTERNAL TIME TIME EXTERNAL TIME EXTERNAL STOP HOLDOFF 1 PERIOD 0 01s gate 0 1s gate 1 0s gate ext gate ext 1 PERIOD ext 0 01s gate ext 0 1s gate ext 1 0s gate TIME EXT 0 01s gate 0 1s gate 1 0s gate ext gate ext 0 01s gate ext 0 1s gate ext 1 0s gate LED indication TIME LED on TIME and EXT LEDs on TIME EXT and HLDF LEDs on TIME LED on TIME and CMPL LEDs on TIME and EXT LED on TIME LED on TIME and EXT LED on TIME EXT and HLDF LEDs on 1 PERIOD LED on 0 01s LED on 0 1s LED on 1 0s LED on EXT LED on EXT and 1 PERIOD LEDs on EXT and 0 01s LEDs on EXT and 0 1s LEDs on EXT and 1 0s LEDs on TIME LED on EXT LED on 0 01s LED on 0 1s LED on 1 0s LED on EXT LED on EXT and 0 01s LEDs on EXT and 0 1s LEDs on EXT and 1 0s LEDs on arming delay or scanning delay gate may be used in this mode see CONFIGURATION MENU and ARMING sections The EXT LED will flash if scanning is enabled the gate time LED will flash if gate width multipl
76. FUNCTIONAL TESTS PERFORMANCE TESTS These tests measure the performance of the SR620 in comparison to its specifications Timebase Frequency This test checks the frequency of the SR620 s 10MHz clock The clock should be recalibrated whenever the frequency deviates significantly from 10MHz 1 Allow the SR620 to warm up for at least 1 2 hour 2 Set the SR620 mode to frequency source to A arming to 1s gate sample size to 1 A trigger level to 0 00V A termination to 50 Ohms 3 Attach the frequency standard to the A input and measure its frequency Record the result Accuracy This test checks that the SR620 will produce the correct result given a known input This test does not check the accuracy of the 10 MHz time base specification 10 MHz 0035 Hz 1 Set the SR620 to Frequency Mode A source 1s gate 1 sample 2 Attach the rear panel 10MHz output to A terminate in 50 Ohms 3 Verify that the reading is consistent with the above specification Record the reading Time Interval This test tests the accuracy of time interval measurements The resolution is also checked specification lt 1ns accuracy lt 50ps rms jitter 1 Set the pulse generator to square wave 4V amplitude frequency to 10 kHz 2 Tee the output of the pulse generator to the A and B inputs of the SR620 using equal length cables from the tee to the inputs 3 Set the SR620 to time mode source A TIME arming 1000 samples
77. HART section may be used to scale the scope display and the PRINT key may be use to generate hardcopy Specification Guide ___ 23 SR620 SPECIFICATION GUIDE This section provides a guide to understanding the SR620 s specifications and their effect on the accuracy and resolution of a measurement First a little terminology TERMINOLOGY LEAST SIGNIFICANT DIGIT LSD The LSD is the smallest displayed increment in a measurement The SR620 has a 4ps single shot LSD and thus the smallest amount that two single shot time interval measurements may differ by is 4ps RESOLUTION Resolution is the smallest difference in a measurement that the SR620 can discern That is the smallest statistically significant change which can be measured by the SR620 Resolution is of primary interest in comparing readings from the same instrument The instrument resolution is limited by many things including short term timebase stability internal noise trigger noise etc Because these processes are random in nature resolution is specified as an rms value rather than a peak value This rms value is the standard deviation of the measured value The SR620 s single shot resolution is typically 25ps rms This number can be improved by averaging over many measurements or in the case of frequency and period measurements increasing the gate time The single shot LSD is always smaller than the single shot resolution ERROR Error is defined as the difference betwe
78. I RE OR DEE TEI ee FIRE ean SIRE SERA 1 10 100 1000 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 Frequency MHz Frequency MHz Input Sensitivity as a function of frequency SR620 Universal Time Interval Counter x Specifications SR620 Universal Time Interval Counter Abridged Command List xi Abridged Command List Syntax Variable i is an integer that selects an input channel for the command i Channel 0 External Gate 1 A input 2 B input Variables i j k l m and n are all integers Variable x is a real number in integer real or exponential notation Commands which may be queried have a in parentheses after the mnemonic The are not sent Commands that may only be queried have a after the mnemonic Commands which may not be queried have no Optional parameters are enclosed by Trigger Control Commands LEVL i x Set channel i threshold to x volts Only allowed in remote operation MTRG j Same as pushing MAN trigger button In external gate or holdoff arming modes n 0 start gate n 1 stop gate Otherwise n is ignored RLVL j Sets the reference output level to O ecl 1 ttl TCPL i j Sets the input ac dc coupling of chans A and B to 0 dc or 1 ac TERM i j Sets the 50 ohm terminator of input also prescaler n 0 50 ohm n 1 1 meg n 2 prescale Prescalers can only be used in freq and per modes TMOD if j Sets autolevel on off 0 auto off 1 auto on TSLP
79. IP 1 4W 2 Isolated Res Network SIP 1 4W 2 Isolated Resistor Network DIP 1 4W 2 8 Ind Printed Circuit Board Printed Circuit Board Transistor TO 92 Package Parts List 97 REF SRS PART VALUE DESCRIPTION Q 201 3 00021 325 2N3904 Transistor TO 92 Package Q 202 3 00021 325 2N3904 Transistor TO 92 Package Q 203 3 00021 325 2N3904 Transistor TO 92 Package Q210 3 00022 325 2N3906 Transistor TO 92 Package Q211 3 00022 325 2N3906 Transistor TO 92 Package Q 212 3 00022 325 2N3906 Transistor TO 92 Package Q 220 3 00021 325 2N3904 Transistor TO 92 Package Q 221 3 00899 327 NE85632 Transistor TO 46 Package Q 222 3 00899 327 NE85632 Transistor TO 46 Package Q 223 3 00027 325 2N5770 Transistor TO 92 Package Q 224 3 00027 325 2N5770 Transistor TO 92 Package Q 225 3 00022 325 2N3906 Transistor TO 92 Package Q 226 3 00021 325 2N3904 Transistor TO 92 Package Q 227 3 00021 325 2N3904 Transistor TO 92 Package Q 228 3 00030 325 J310 Transistor TO 92 Package Q 229 3 00029 325 2N5951 Transistor TO 92 Package Q 306 3 00021 325 2N3904 Transistor TO 92 Package Q 307 3 00021 325 2N3904 Transistor TO 92 Package Q 308 3 00021 325 2N3904 Transistor TO 92 Package Q 309 3 00027 325 2N5770 Transistor TO 92 Package Q 401 3 00030 325 J310 Transistor TO 92 Package Q 402 3 00021 325 2N3904 Transistor TO 92 Package Q 403 3 00018 324 MRF904 Transistor TO 72 Package Q 404 3 00018 324 MRF904 Transistor TO 72 Package Q 405 3 00022 325 2N390
80. MHz is low and U314A will behave like a one shot providing a 10 MHz pulse train to the phase comparator The output of the phase comparator is filtered by the 6 dB octave differential active filter U316 and associated R s and C s The filtered output of the phase comparator is used to control the frequency of the crystal oscillator when Int_Clk is high Otherwise a dc voltage V_Freq sets the oscillator frequency V_Freq may be adjusted in the CAL portion of the configuration menu If the filtered output goes above 5 Vdc or below 5 Vdc then the comparator bit Bad_Clk will go low and the processor will light the Clock LED on the front panel FRONT END INPUTS Sheet 8 of 16 The front end circuitry is used to discriminate the A B and EXT inputs into ECL levels The inputs may be ac or dc coupled except for the EXT input which is always dc coupled terminated into 1 M or 50 Ohms and compared to levels from 5 to 5 Vdc with 10 mV resolution Input overloads are detected to protect the 50 Ohm terminators and a UHF prescaler allows frequency measurements to 1 3 GHz SR620 Universal Time Interval Counter 80 Circuit Description The three inputs are nearly identical reference designations for channel A will be used in the description that follows The inputs are terminated to 50 Ohms by the processor activating relay U401 Both poles of the DPDT relay are used to reduce inductance The 50 Ohm terminator is a 1
81. MODEL SR620 Universal Time Interval Counter S RS Stanford Research Systems 1290 D Reamwood Avenue Sunnyvale California 94089 Phone 408 744 9040 Fax 408 744 9049 email info thinkSRS com www thinkSRS com Copyright 1989 by SRS Inc All Rights Reserved Revision 2 7 2 2006 SR620 Universal Time Interval Counter Table of Contents i Table of Contents Condensed Information Width Arming 13 WIDTH TIME 13 Safety and Use V WIDTH TIME EXT 13 SRS Symbols vi WIDTH TIME EXT with HLDF 13 Specifications vii Abridged Command List xi Rise and Fall Time Arming 13 RISE FALL TIME 13 Operation RISE FALL EXT 13 Quick Start Instructions 1 Frequency Arming 14 Instrument Overview 2 Frequency Ratio 14 Front Panel Operation 3 Period Arming 14 Period Ratio 14 Choosing the Measurement 3 Setting the Mode 3 Phase Arming 14 Setting the Source 3 Setting the Arming Mode 3 Count Arming 15 Setting the Number of Samples 3 Count Ratio 15 Starting Measurements 3 Arming Mode Summary 4 Delayed Arming Modes 15 Choosing the Output Display 5 Configuration Menus 17 Setting the Front Panel Display 5 Graphics Outputs 6 CONTROL Menu 17 Graph Types 6 GPIB Parameters 17 Scaling Graphs 6 RS232 Parameters 17 Graphics Cursor 6 Graphics Zoom 6 CALIBRATION Menu 17 Hardcopy Output 7 AutoCal 18 Chart Outputs 7 Clock Source 18 Setting the Inputs 9 OUTPUT Menu 18 Setting Trigger Levels 9 Graphics Enable 18 Setting Trigger Slopes 9 Printer Plotter Con
82. MPLES 0 THEN STOP 320 IF SAMPLES gt 2000 THEN GOTO 280 330 setup dma parameters 340 350 MODE amp H2105 dma mode 360 COUNT 8 SAMPLES 370 SEGMENT 1 380 C BD S TIC command 390 400 dma data into PC 410 CALL SEND SR620 C STATUS GOSUB 890 SEND COMMAND 420 CALL TRANSMIT TALK STATUS GOSUB 890 MAKE TIC A TALKER 430 OFS VARPTR DAT 1 440 CALL DMA2 SEGMENT OFS COUNT MODE STATUS GOSUB 890 450 460 get mode so we ll know which conversion factor to use 470 CALL SEND SR620 MD STATUS GOSUB 890 480 ANS SPACE 50 SR620 Universal Time Interval Counter Programming Examples ___ 47 490 CALL ENTER ANS LENGTH SR620 STATUS GOSUB 890 get answer 500 TMODE VAL ANS TIC mode 510 CALL SEND SR620 EXPD STATUS GOSUB 890 520 ANS SPACE 50 530 CALL ENTER ANS LENGTH SR620 STATUS GOSUB 890 540 TEXPD VAL ANS 550 560 570 convert data to correct format 580 590 get 8 bytes 4 2bytes corresponding to one sample 600 FOR I 1 TO SAMPLES 610 SIGN 0 620 FDATA I O 630 FORJ 1TO4 640 TEMP J DAT 4 l 1 J 650 IF TEMP J lt 0 THEN TEMP J 65536 TEMP J 660 NEXT J 670 if answer lt 0 change sign and get magnitude 680 IF DAT 4 I 1 4 gt 0 GOTO 740 690 SIGN 1 700 FORJ 1T04 710 TEMP J 65535 TEMP J 720 NEXTJ 730 convert to floating point 740 FORJ 1TO4 750 FDATA l FDATA
83. One way to read back every point of a scan is to continually send the command SCAV j until a legal value results and then move on to the next point The number returned is a floating point number with up to 16 digits of precision SCUT j The SCJT query returns the value of point j of the jitter graph or scan point j J has the range of 1 to 250 This query returns the illegal value 9E20 if the stripchart is blank or the scan has not reached point j One way to read back every point of a scan is to continually send the command SCAV j until a legal value results and then move on to the next point The number returned is a floating point number with up to 15 digits of precision BDMP j The BDMP command puts the SR620 into its high speed binary dump mode j specifies the number of points to be dumped and may range from 1 to 65535 THIS COMMAND FUNCTIONS ONLY ON GPIB At the maximum baud rate RS232 would offer no speed improvement so this command is not functional on RS232 On receipt of the BDMP command the SR620 does the following 1 the display shows the message BINARY OUTPUT 2 the SR620 automatically enters automeasure mode with a sample size of one and 3 disables the keyboard except for the RESET key SR620 Universal Time Interval Counter 34 Programming Commands Once in binary dump mode the SR620 will take data and send it to the controller as fast as it can Binary dump mode is terminated when the count expi
84. PM Resistor Wire Wound Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 REF SRS PART VALUE R 934 4 00042 401 15K R 935 4 00034 401 10K R 936 4 00021 401 1 0K R 937 4 00032 401 100K R 938 4 00034 401 10K R 940 4 00021 401 1 0K R 941 4 00138 407 10 0K R 942 4 00164 407 20 0K R 943 4 00030 401 10 R 944 4 00417 407 2 74K R 945 4 00169 407 249 R 946 4 00439 407 1 33K R 947 4 00149 407 121 R 1001 4 00130 407 1 00K R1002 4 00032 401 100K R 1003 4 00176 407 3 01K R1004 4 00031 401 100 R1005 4 00031 401 100 RU130 4 00021 401 1 0K 0103 1 00026 150 28 PIN 600 MIL SW201 1 00045 130 3 PIN STRAIGHT T 1001 6 00039 610 SR620 FS700 U1A 6 00184 623 10 MHZ 1PPM U 101 3 00216 340 Z8800 U 102 3 00259 340 74HCT373 U 104 3 00299 341 32KX8 70L U 105 3 00261 340 74LS245 U 106 3 00158 340 74HC154N U 107 3 00037 340 74HC138 U 108 3 00155 340 74HC04 U 109 3 00045 340 74HC32 U 110 3 00045 340 74HC32 U 114 3 00261 340 74LS245 U 115 3 00044 340 74HC244 U 116 3 00044 340 74HC244 U 117 3 00157 341 8KX8 100 LOW U 118 3 00298 340 Z84C0008PEC U 119 3 00058 340 AD7524 U 120 3 00058 340 AD7524 U 121 3 00087 340 LF347 U 122 3 00645 340 NAT9914BPD U 123 3 00078 340 DS75160A U 124 3 00079 340 D
85. Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg nnn nnn nnn nnn nn nn nn nw NLT g Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg SRS sub assemblies Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Relay Relay Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Relay Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Relay Relay Integrated Circuit Thru hole Pkg REF SRS PART VALUE U 414 3 00066 340 CA3140E U 415 3 00196 335 HS 212S 5 U 417 3 00143 340 LM393 U 418 3 00294 340 AD96685 U 421 3 00196 335 HS 212S 5 U 424 3 00066 340 CA3140E U 425 3 00196 335 HS 212S 5 U 427 3 00143 340 LM393 U 428 3 00294 340 AD96685 U 430 3 00180 340 MC10H107 U 501 3 00268 340 MC10H164 U 502 3 00268 340 MC10H164 U 503 3 00268 340 MC10H164 U 504 3 00269 340 MC10H158 U 505 3 00201 340 MC10H105 U 506 3 00194 340 MC10H131 U 507 3 00201 340 MC10H105 U 508 3 00194 340 MC10H131 U 509 3 00194 340 MC10H131 U 510 3 00180 340 MC10H107 U 511 3 00194 340 MC10H131 U 512 3 00194 340 MC10H131 U 513 3 00151 340 MC10125 U 514 3 00238 340 74F74 U 550 3 00200 340 MC10124 U 602 3 00201 340 MC10H1
86. Push the up arrow key again and all of the segments of all 16 digits should light 4 Press the up arrow key repeatedly to light each front panel indicator LED in turn top to bottom left to right At any time only a single LED should be on 5 After all of the LED have been lit further pressing of the front panel keys will display the key code associated with each key Each key should have a different keycode Internal Self Tests The internal self tests test the functionality of the system RAM the CPU the video RAM the two internal counter channels and the time interval calibration 1 Turn on the SR620 The model number the ROM firmware version number and the serial number should be displayed for about 3 seconds Then the message SELF TEST PASS should appear If a TEST ERROR message appears see the TROUBLESHOOT ING section for a description of the errors Test errors 33 and 34 indicate loss of calibration and may be fixed by running the Autocal procedure see CONFIGURATION MENU section Trigger Input Tests These tests test the EXT A and B trigger inputs and the REF output 1 Set the SR620 mode to FREQ source to A B arming to EXT Automeasure off hold down RESET button until AUTO LED goes off and display to TRIG to display the trigger levels on the front panel 2 Set the REF output to TTL and display the output on a scope terminated into 1 Mohm The scope should display a 1kHz square wave SR620 Univ
87. Q403 pair The buffered outputs of A and B are normally sent to comparators U408 and U418 respectively by the relays U405 and U415 The relays are configured so as to reduce crosstalk between the A amp B inputs In the case of rise and fall time measurements one input signal is sent to both comparators which are set for the low and high voltage levels for the transition being measured The comparator U408 is operated in a Schmitt trigger configuration with about 20 mV of hysteresis Since the input signal has been attenuated by 2x this represents 40 mV of hysteresis at the input The comparator threshold is set by the output of U406A which serves as a SR620 Universal Time Interval Counter sample and hold amplifier for C409 The comparator provides inverted and non inverted outputs to the ECL multiplexers on sheet 9 of 16 The multiplexers chooses one or the other to trigger on rising or falling edges of the input signal TRIGGER MULTIPLEXERS Sheet 9 of 16 Nine bits FREQx STARTx and STOPx from the processor control the signal source to be used in time interval and frequency measurements For time interval measurements U502 and U503 can select either the A or B inputs either polarity to form either the start or stop signal The 1 000KHz CAL signal may also be selected U501 can select from the same signals for frequency measurements If a frequency measurement is to be done U502 and U503 will select Freq_Start and F
88. R620 to time mode Set the A input to1 Mohm slope and the A trigger threshold to 0 00V 3 Set the D A output to 1 0V and slowly increase the voltage until the A TRIG LED flashes Record this voltmeter reading The voltage should be 0 00V 15mV 4 Set the A trigger level to 4V Slowly increase the D A 0 voltage from O V until the A TRIG LED flashes Record this voltage The voltage should be 4 0V 30mV SR620 Universal Time Interval Counter 5 Set the A trigger level to AUTO and the D A 0 to 1V Read the trigger level Record this result The value should be 1 0V 50mV 6 Repeat steps 2 3 4 and 5 for channel B and record the results D A Output Accuracy These tests verify the accuracy of the rear panel D A outputs specification 0 3 full scale 30mV 1 Connect the voltmeter to the D A O output 2 In the Scn submenu of the SR620 s configuration menus set the two D A outputs to D A mode not chart 3 Set D A 0 to 10 00V Measure the output voltage and record the result Verify that the reading is 10 00V 30mV 4 Set D A 0 to 0 00V Measure the output voltage and record the result Verify that the reading is 0 00V 30mV 5 Set D A O to 10 00V Measure the output voltage and record the result Verify that the reading is 10 00V 30mV 6 Repeat steps 3 4 and 5 for D A output 1 Record the results DVM Input Accuracy These tests verify the accuracy of the DVM inputs specification 0 3 full
89. Rectangular D 13 3 00012 306 GREEN LED Rectangular D14 3 00012 306 GREEN LED Rectangular D15 3 00012 306 GREEN LED Rectangular D 16 3 00012 306 GREEN LED Rectangular D 17 3 00012 306 GREEN LED Rectangular D18 3 00012 306 GREEN LED Rectangular D19 3 00012 306 GREEN LED Rectangular D 20 3 00004 301 1N4148 Diode D 21 3 00012 306 GREEN LED Rectangular D 22 3 00012 306 GREEN LED Rectangular D 23 3 00012 306 GREEN LED Rectangular D 24 3 00012 306 GREEN LED Rectangular D 25 3 00012 306 GREEN LED Rectangular D 26 3 00012 306 GREEN LED Rectangular D 27 3 00012 306 GREEN LED Rectangular D 28 3 00012 306 GREEN LED Rectangular D 29 3 00012 306 GREEN LED Rectangular D 30 3 00004 301 1N4148 Diode D 31 3 00012 306 GREEN LED Rectangular D 33 3 00012 306 GREEN LED Rectangular D 34 3 00012 306 GREEN LED Rectangular D 35 3 00012 306 GREEN LED Rectangular D 36 3 00012 306 GREEN LED Rectangular D 37 3 00012 306 GREEN LED Rectangular D 38 3 00012 306 GREEN LED Rectangular D 39 3 00012 306 GREEN LED Rectangular D 40 3 00004 301 1N4148 Diode D 41 3 00012 306 GREEN LED Rectangular D 42 3 00884 306 RED LED Rectangular D 43 3 00012 306 GREEN LED Rectangular D 44 3 00012 306 GREEN LED Rectangular D 45 3 00012 306 GREEN LED Rectangular D 46 3 00012 306 GREEN LED Rectangular SR620 Universal Time Interval Counter 88 Parts List REF SRS PART VALUE DESCRIPTION D 47 3 00012 306 GREEN LED Rectangular D 48 3 00012 306 GREEN LED
90. Resistor Carbon Film 1 4W 5 R 733 4 00034 401 10K Resistor Carbon Film 1 4W 5 R 734 4 00472 407 806 Resistor Metal Film 1 8W 1 50PPM R 735 4 00034 401 10K Resistor Carbon Film 1 4W 5 R 736 4 00473 407 11 0K Resistor Metal Film 1 8W 1 50PPM R 744 4 00176 407 3 01K Resistor Metal Film 1 8W 1 50PPM R 746 4 00466 407 1 87K Resistor Metal Film 1 8W 1 50PPM R 748 4 00176 407 3 01K Resistor Metal Film 1 8W 1 50PPM R 750 4 00466 407 1 87K Resistor Metal Film 1 8W 1 50PPM R 801 4 00430 407 665K Resistor Metal Film 1 8W 1 50PPM R 802 4 00430 407 665K Resistor Metal Film 1 8W 1 50PPM R 803 4 00431 407 332K Resistor Metal Film 1 8W 1 50PPM R 804 4 00431 407 332K Resistor Metal Film 1 8W 1 50PPM R 805 4 00430 407 665K Resistor Metal Film 1 8W 1 50PPM R 806 4 00430 407 665K Resistor Metal Film 1 8W 1 50PPM R 807 4 00431 407 332K Resistor Metal Film 1 8W 1 50PPM R 808 4 00431 407 332K Resistor Metal Film 1 8W 1 50PPM R 810 4 00398 407 499K Resistor Metal Film 1 8W 1 50PPM R 811 4 00432 407 56 2K Resistor Metal Film 1 8W 1 50PPM R 812 4 00158 407 2 00K Resistor Metal Film 1 8W 1 50PPM R 814 4 00138 407 10 0K Resistor Metal Film 1 8W 1 50PPM R 815 4 00138 407 10 0K Resistor Metal Film 1 8W 1 50PPM R 816 4 00218 408 10 00K Resistor Metal Film 1 8W 0 1 25ppm R 817 4 00434 408 4 990K Resistor Metal Film 1 8W 0 1 25ppm R 818 4 00435 408 10 20K Resistor
91. S75161A U 125 3 00110 340 MC1489 U 126 3 00109 340 MC1488 U 127 3 00263 340 DS75451N U 128 3 00261 340 74LS245 U 130 3 00155 340 74HC04 U 131 3 00199 340 74HC4538 U 201 3 00044 340 74HC244 U 202 3 00044 340 74HC244 DESCRIPTION Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Parts List Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Socket THRU HOLE Connector Male Transformer Temp Controlled Crystal Osc Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg STATIC RAM I C Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg STATIC RAM I C Integrated Circuit Thru hole Pkg
92. T measurement is completed CURS 7 j The CURS command sets the cursor position to j 1 250 If the graph is empty or the stripchart has not yet reached point j an error is returned DGPH j The DGPH command sets the displayed graph If j O the histogram is displayed if j 1 the mean stripchart is displayed and if j 2 the jitter stripchart is displayed GCLR The GCLR command clears the graphs If a scan is in progress GCLR does NOT clear the scan The SCLR command clears both the scan and the graphs GENA j The GENA command sets the graph enable status If j O the graphs are turned OFF Ifj 1 the graphs are turned ON Turning the graphs off can dramatically improve the SR620 s measurement throughput see details in the Programming Examples section GSCL j x The GSCL command sets the scales for the graphs The parameter j selects the scale to be set according to the following table SR620 Universal Time Interval Counter 36 Programming Commands j scale 0 histogram vertical 1 histogram horizontal 2 histogram bins 3 mean vertical 4 jitter vertical The parameter x is the desired units division example for 100ns div x 100E 9 The scale values are all positive numbers except that a negative value for the histogram vertical scale will set the scale to log mode An error will occur if an attempt is made to set the scale to an illegal value This can happen for example for cer
93. The SR620 is mostly self calibrating The AutoCal procedure may be run to adjust most of the calibration constants to their correct value An important exception to this is the adjustment of the 10 MHz timebase See calibration procedure for adjusting timebase frequency To run the AutoCal procedure select the Autocal line in the CAL submenu of the CONFIG menu and push the START button The procedure will finish in about two minutes with the message Cal done See the troubleshooting section of the manual if a error occurs Autocal should be run every 1000 operating hours or if the environmental operating conditions change significantly It may also be run before critical measurements to insure optimum instrument performance CALBYTES The calbytes adjust for unit to unit variations which are very stable Most of the calibration is automatic there are only a few manual calibration procedures The calbytes may be viewed and adjusted by putting the cal enable jumper inside the SR620 at the front center of the circuit board into the enable position and then looking at the Caldat line in the Cal submenu The function of the calbytes are given in the table here Calibration Procedure 69 Calbyte Function 0 Start TAC gain adjust 1 Start TAC zero offset 2 Stop TAC gain adjust 3 Stop TAC zero offset 4 10MHz oscillator adjustment 5 6 7 Ext A B comparator gain adjustment 8 9 10 Ext A B positive slope zero
94. WBN O TST The TST common query runs the selt test procedure The query will return the following status value value meaning 0 no error 4 cpu error 5 system ram error 6 video ram error 16 count gate error 17 chan 2 count 4 0 18 chan 1 count error 19 chan 1 count 4 0 20 chan 2 count error 32 frequency gate error 33 excessive jitter 34 frequency insertion delay error 35 time interval insertion delay error Errors 33 35 can usually be eliminated by running the autocal procedure The other errors are usually caused by hardware problems SR620 Universal Time Interval Counter BYTE 7 j k The BYTE command set the value of linearization byte j to k Parameter j may have a value from O to 129 and k may range from 0 to 255 NOTE this command will alter the calibration of the SR620 However running autocal will correct the problem WORD 7 j k The WORD command sets the value of calibration word j to k Parameter j may have a value from 0 to 51 while k may range from 0 to 65535 NOTE this command will alter the calibration of the the SR620 To correct the calibration the factory calibration bytes may be recalled see the Calibration section STATUS BYTE DEFINITIONS Status Reporting The SR620 reports on its status by means of four status bytes the serial poll byte the standard status byte the TIC status byte and the error status byte On power on the SR620 may either clear all of its s
95. WER SUPPLY REGULATORS Sheet 14 of 16 The voltage regulators provide outputs at 15 5 2 0 5 2 and 15 Vdc from the UNREGULATED power The high current regulators 5 5 2 and 2 V are designed to operate with a very low drop out voltage All of the regulated outputs are current limited for short circuit protection All three high current regulators are essentially the same circuit references in the following description refer to the 5 0 Vdc supply The main pass transistor is Q901 the base of this transistor is controlled so that the emitter will provide a low impedance source of 5 Vdc The current gain of Q901 remains large until the collector emitter voltage drops to about 0 4 vdc hence the low drop out voltage for the regulator The base of Q901 is driven by the emitter of Q902 which is driven by the output of the op amp U902A By comparing the output of the regulator to the 5 00 vdc reference the op amp maintains the regulator s output at 5 00 vdc The current output from the regulator is measured by R901 a 0 1 Ohm resistor If the current exceeds about 2 7 Amps then the comparator U901A turns on pulling the reference input below ground thereby turning off the regulator s output U909 and U910 are regulators for 15 vdc If the power switch SW901 is opened then the output of these regulators drops to about 1 25 volts turning off the instrument The unregulated power is not turned off so that the regulat
96. ae x E a A di a o 10 s e 2 us wae d yia ai we og gt E er al 10 79 slew rate 10 Vius Pr a y ii sae ee ae pe 10 h pa A slew rate 0 1 V ns A ui SE za slew rate 1 V ns FA 10 ee errr meor 10 10 103 10 2 10 Input Signal Noise V rms Graph 3 Effect of input noise on measurement resolution Averaging reduces the effects of noise MEASUREMENT ACCURACY Trigger Timing Error ns Trigger Timing Error vs Input Slew Rate rer ry rrr 10 Slew Rate V us Graph 4 Effect of input slew rate on measurement error The following equations allow one to calculate the SR620 s resolution and error in the various measurement modes The SR620 s typical specification are used in the following equations For worst case bounds simply replace the typical with the worst case numbers NOTE The quantities added to calculate the SR620 s resolution are independent rms quantities and must be added in quadrature total X x NOTE timebase error refers to the sum of aging and temperature effects TIME INTERVAL WIDTH RISE FALL TIME MODES In the time measurement modes the measurement resolution and error are given by N number of samples averaged Resolution 25 ps time interval x short term stability start trigger jitter stop trigger jitter Error resolution timebase error x time interval start trigger level
97. albyte 39 until the answer reads 0 11 Attach the non inverting output of the power splitter to A and the inverting output to B SR620 Universal Time Interval Counter 72 Calibration Procedure 12 Set the A slope to and the B slope to and measure the time interval Adjust calbyte 37 until the answer reads 0 13 Set the A slope to and the B slope to and measure the time interval Adjust calbyte 38 until the answer reads 0 14 Set the source to REF and attach the known length cable from REF to B 15 Set the A and B slopes to and measure the time interval Adjust calbyte 32 until the known value of the cable length is shown 16 Set the A and B slopes to and measure the time interval Adjust calbyte 35 until the known value of the cable length is shown 17 Set the A slope to and the B slope to and measure the time interval Adjust calbyte 33 until the known length 500us is shown 18 Set the A slope to and the B slope to and measure the time interval Adjust calbyte 34 until the known length 500us is shown Rise Fall Time Mode 1 Set the mode to rise fall time arming to time Set both A and B trigger thresholds to the same value 2 Set the source to A and attach the pulse generator to A 3 Set the slopes to and measure the rise time Adjust calbyte 46 until the answer reads 0 4 Set the slopes to and measure the fall time adjust calbyte 47 until the answer reads 0 5 S
98. alibrating the SR620 Note The factory value for a particular calbyte may be recalled from ROM by displaying the calbyte and pressing the CLR REL button The factory value for all of the calbytes may be recalled by pressing the CLR button in the SCOPE and CHART section Simple Calibration It is rare that the SR620 will need a complete recalibration In virtually all cases this simple calibration procedure will suffice Procedure 1 Run Autocal 2 To calibrate the timebase attach a precision 10MHz source to the A input Measure its frequency with a 1s gate Adjust calbyte 4 until the display reads exactly 10 0MHz The allowable range of calbyte 4 is O to 4095 all other numbers are set modulo 4096 If with the oven oscillator the frequency cannot be set with the calbyte remaining in range set the calbyte to midrange and adjust the coarse adjustment screw on the oscillator until the frequency is correct Note Attach a x y scope to the SR620 and look at the histogram display The mean value can be read off of the histogram while the calbyte is viewed and adjusted on the front panel Complete Calibration Procedure Note All or any part of this procedure may be done SR620 Universal Time Interval Counter Necessary Equipment 1 100MHz or faster oscilloscope 2 10 20MHz pulse generator with 5ns or less transition times such as Hewlett Packard HP8012 3 Precision DC voltmeter such as Fluke 8840A 4 0 20
99. amic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Ceramic Disc 50V 10 SL Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Ceramic Disc 50V 10 SL Cap Monolythic Ceramic 50V 20 Z5U Capacitor Ceramic Disc 50V 10 SL Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 50V 20 Rad Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 50V 20 Rad Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 50V 20 Rad Capacitor Polystyrene 50V 5 Rad Cap Polyester Film 50V 5 40 85c Rad Capacitor Ceramic Disc 50V 10 SL Capacitor Tantalum 50V 20 Rad Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Capacitor Ceramic Disc 50V 10 SL Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Capacitor Ceramic Disc 50V 10 SL Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Capacitor Tantalum 35V 20 Rad Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 35V 20 Rad Cap Mini Electrolytic 50V 20 Radial Cap Mini Electrolytic 50V 20 Radial Capacitor Tantalum 50V 20 Rad
100. and the speed of the computer and its interface drivers About 1400 measurements per second may be transferred to a computer using a DMA Direct Memory Access GPIB controller to measure time intervals in the binary dump mode SR620 Universal Time Interval Counter 44 Programming Examples Program Example 1 IBM PC BASIC via RS232 In this example the IBM PC s COM2 serial port is used to communicate with the SR620 The program sets up the SR620 and then starts measurements and reads the results Only pins 2 3 and 7 of the PC s port need to be connected to the SR620 10 Example program to start a measurement and read the result This 20 program uses IBM Basic and communicates via the COM2 RS232 port 30 40 set up the SR620 for 9600 baud 8 bits no parity 50 OPEN COM2 9600 N 8 2 CS DS CD AS 1 60 70 setup COM2 for 9600 baud no parity 8 data bits 2 stop bits 80 ignore cts dsr and cd 90 100 PRINT 1 clear COM2 105 clear TIC set to width of ref 10 samples automeasure off 110 PRINT 1 RST MODE1 SRCE2 SIZE10 AUTMO 120 PRINT 1 STRT WAI XAVG start measurement wait until done read 130 INPUT 1 TIME read double precision answer 140 PRINT width TIME 150 GOTO 120 loop forever Tips on Interfacing to PC s using a National Instrument GPIB Card To succesfully interface the SR620 to a PC via the GPIB the instrument interface card and interface drivers must all be configured p
101. aph 2 shows the non linearity over the time range of 0 to 11ms For times greater than 11ms the non linearity is dominated by the timebase error SR620 Universal Time Interval Counter 24 Specification Guide Differential Non linearity vs Time t 0 11ns Differential Non linearity vs Time t 0 12us Differential Non linearity ps Differential Non Linearity ps A Ml Oe a Sp N 6 Time Interval us 4 6 Time Interval ns Graph 1 Differential Non linearity for time Graph 2 Differential Non linearity for time differences of O to 11 ns This shows the differences of O to 11ms residual non linearity of the time to amplitude converters TIMEBASE SPECIFICATIONS The specifications of the timebase affect both the resolution and error of measurements made with the SR620 A timebase may be specified by two parameters its short term stability and its long term stability SHORT TERM STABILITY The short term stability of an oscillator is a measure of the changes in the output frequency of the oscillator on a short time scale seconds or less These changes in the frequency are usually random and are due to internal oscillator noise output level modulation etc These random changes in frequency affect the resolution of the measurement just as other internal noise does The short term stability of an oscillator is usually characterized by specifying either its Allan variance or its phase noise The SR6
102. ator oven oscillator aging 1x10 6 yr 5x10719 day temperature response 1x10 0 to 50 C 5x10 9 0 to 50 C So for example with the oven oscillator 30 days after calibration the oscillator may have drifted at most 30 x 5x10 1 x 10MHz 0 15Hz Also a worst case temperature variation must be assumed when evaluating the worst case error That is for example the optional oscillator must be assumed to be at worst 5ppb in error because the conditions when the SR620 was calibrated are unknown EXTERNAL TIMEBASES The SR620 has a rear panel input that will accept either a 5 or 10Mhz external timebase The SR620 phase locks its internal timebase to this reference The phase locked loop has a bandwidth of about 20Hz and thus the characteristics the the SR620 s clock for measurement times longer than 50ms become that of the external source For shorter measurement times the clock characteristics are unimportant compared to the internal jitter 25ps rms of the SR620 Thus if the signal from a Cesium clock is input into a SR620 with a standard TCXO oscillator the short term and long term stability of the SR620 will become that of the Cesium clock TRIGGER INPUT SPECIFICATIONS There are two ways that the inputs can affect the resolution and accuracy of a measurement The first is called trigger jitter and is due to random noise on the A and B input signals and the trigger input buffers This random noise causes the input to trigger at a time different
103. bits are 0 1 d a output mode chart d a 2 graph on off 3 6 scan points 7 ref output level same as WAIT command 0 3 stepsize corresponding to 1E 6 2E 6 etc 4 5 delay scan enable 21 22 scan starting delay bytes 1 0 delay step size 256 byte1 byte0 23 24 25 scan holdtime bytes 2 1 0 hold 65536 byte2 256 byte1 byteO ONOaRWND setup byte 2 setup byte 3 rs232 wait scan setup byte SR620 Universal Time Interval Counter Programming Commands 39 LOCL j The LOCL command sets the RS232 local remote function If j O the SR620 is local if j 1 the SR620 will go remote and if j 2 the SR620 will go into local lockout state The states duplicate the GPIB local remote states in the LOCAL state both command execution and keyboard input are allowed In the REMOTE state command execution is allowed but the keyboard and knobs are locked out except for the LOCAL key which returns the SR620 to the local state In the LOCAL LOCKOUT state all front panel I O is locked out including the LOCAL key WAIT 2 j The WAIT command sets the RS 232 transmission delay between characters This is useful for slower computers and terminal programs The delay is equal to 2ms times the parameter j 0 lt j lt 25 Status Reporting Commands See tables at the end of the Programming section for Status Byte definitions CLS The CLS common command clears all status registers This command does not affect
104. bon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 2W 1 50ppm Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 8W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Fil
105. cify the Plot Port as GPIB or RS 232 If you specify GPIB for the Plot Port then you need to set the plotter s GPIB address If RS 232 is specified the BAUD rate is fixed at 9600 For more details see the section on CONFIG GPIB INTERFACE PROBLEMS For proper operation the GPIB address of SR620 must be set to match that expected by the controlling computer The default GPIB address is 16 and so it is a good idea to use this address when writing programs for the SR620 Any address from 0 to 30 may be set in the CONFIG menu To check the GPIB address press the SEL key in the CONFIG section to select the ctrl menu Then press the SET key twice to view the GPIB address The up down keys in the SCOPE AND CHART section may be used to set the GPIB address The SR620 will ignore its front panel key pad when Remote Enable REN has been asserted by the GPIB This REMOTE state is indicated by the REM LED in the STATUS section To return to LOCAL operation ie to enable the front panel press the SEL key in the CONFIG section Controlling programs may inhibit the ability to return to LOCAL operation by asserting the Local Lockout state LLO A linefeed character is sent with and End or Identify EOI to terminate strings from the SR620 Troubleshooting Tips __59 Be certain that your GPIB controller has been configured to accept this sequence RS 232 PROBLEMS The RS 232 baud rate number of bits per character and par
106. counter status byte If the parameter j is present the value of bit j is returned Reading this register will clear it while reading bit j will clear just bit j TENA j The TENA command sets the time interval counter status enable register to the decimal value j Calibration Commands NOTE These commands are primarily intended for factory calibration use and should never be needed during normal operation Incorrect use of some of these commands can destroy the calibration of the SR620 TAC j The TAC query reads the value of the time to amplitude converters The parameter j O refers to the start channel while j 1 refers to the stop channel SR620 Universal Time Interval Counter 40 Programming Commands PHK j The PHK command is used to exercise the printer port handshaking lines The value of j 0 or 1 sets the state of the init and strobe lines The query PHK reads the value of the busy line POT j The POT query reads the dc voltage of the front panel potentiometers NOT the trigger level in units of 10mvV CAL The CAL common query runs the autocal procedure This query will return the following status value no error SR620 not warmed up can t cal no trigger error can t find edge on start tac can t find edge on start fine seek start tac calbyte out of range start tac non convergence Start linearity byte out of range 9 23 stop tac errors same as start value n 16 SsaNOOR
107. crosoft s FORTRAN for PC compatibles is used to program the time interval counter via National Instrument s GPIB interface card C Example program demonstrating programming the SR620 over the GPIB using C the National Instruments GPIB card The program sets up the SR620 and C then starts taking data C C This program is written in Microsoft FORTRAN v4 0 To use the National C card the National device driver must be installed and the IBCONF program C must be run to tell the driver where everything is The program is compiled C with the command FL AL FPa example2 for and the resulting object file is C linked with the file MFIBL OBJ supplied by National storage 2 C this line must be in the source file common ibglob ibsta iberr ibent integer 2 sr620 character 80 data real 8 answer C initialize gpib card call ibinit ibsta C get device id for sr620 sr620 ibfind SR620 C setup TIC call ibwrt sr620 RST MODE1 SRCE2 SIZE10 AUTMO n c 30 C start measurement 100 call ibwrt sr620 STRT WAI XAVG n c 16 C read answer data call ibrd sr620 data 20 read data 1000 answer 1000 format bn 1D22 16 write answer C continue forever goto 100 end SR620 Universal Time Interval Counter 46 Programming Examples Program Example 3 IBM PC IBM Basic CEC GPIB Card This example takes data in the binary dump mode and converts it into the correct units This program is written in IBM BASIC and uses a
108. ct even odd or none 7 rS232dLly 0 Dwell time x2 ms between characters 5 rS232bitS 8 6 rS 232 PAr nonE CALIBRATION MENU cAL This menu is used to calibrate the instrument and to select the source for the timebase Calibration and Clock Source Menu Line Default Display Comments 1 Auto cAL Press START key for Autocal procedure Select Timebase source int rear Specify Ext timebase frequency 5 10 MHz 4 cALdAt 000 01947 Access to 180 calibration words 2 cLoc SourcE int 3 cLoc Fr The Autocal procedure is used to null insertion delay differences between the start and stop SR620 Universal Time Interval Counter 18 Configuration Menus channels and to reduce the differential non linearity of the analog interpolators It may be done whenever the instrument is completely warmed up and should be done once a year or after 1000 operating hours It is recommended that the EXT A and B inputs be disconnected while Autocal is running To run Autocal allow the SR620 to warm up for at least 1 2 hour press the START button in the SAMPLE SIZE section This procedure may not be started until the red CLOCK LED in the CONFIG section goes off otherwise a cAL Error 01 will result The autocal procedure takes about two minutes to run and ends with the message cAL donE then returns to taking measurements See the TROUBLESHOOTING if cal errors occur The Autocal procedure may be stoppe
109. d Res Network SIP 1 4W 2 Isolated Res Network SIP 1 4W 2 Isolated Res Network SIP 1 4W 2 Isolated Res Network SIP 1 4W 2 Isolated Res Network SIP 1 4W 2 Isolated Res Network SIP 1 4W 2 Isolated Res Network SIP 1 4W 2 Isolated Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Res Network SIP 1 4W 2 Isolated Res Network SIP 1 4W 2 Isolated Res Network SIP 1 4W 2 Isolated Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common YS FS SF YS NS SF SS a Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Res Network SIP 1 4W 2 Isolated Res Network SIP 1 4W 2 Isolated Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Resistor Network SIP 1 4W 2 Common Res Network SIP 1 4W 2 Isolated Res Network SIP 1 4W 2 Isolated Res Network SIP 1 4W 2 Isolated Res Network SIP 1 4W 2 Isolated Res Network SIP 1 4W 2 Isolated E ee Sp en Res Network SIP 1 4W 2 Isolated Res Network S
110. d by pressing the reset key None of the SR620 s calibration constants are changed until autocal is complete so stopping in the middle will not affect the SR620 s calibration The cloc SourcE selects the timebase source The up down buttons may be used to select between the internal int or external rear timebases If an external timebase is selected then the frequency must be specified as either 5 or 10 MHz When an external timebase is selected the SR620 will phase lock its crystal oscillator to the external source If it cannot lock to the external source then the red CLOCK LED will turn on in the CONFIG section This LED is ALWAYS on for the first few minutes of operation Failure to phaselock may be due to any to the following 1 External reference has insufficient amplitude stability or accuracy 2 the wrong frequency was specified in the cLoc Fr menu 3 the optional ovenized oscillator needs to be adjusted to be within lock range of the external source The cALdAt line allows the user to adjust the SR620 s 180 calibration bytes provided that the cal enable jumper on the main circuit board is in the enable position If the jumper is in the disable position this menu line will not appear The meaning of these calibration bytes is described in the CALIBRATION section of this manual OUTPUT MENU out The output menu enables scope displays selects the hardcopy device sets the DVM scales chooses a jit
111. dge of Circuit Description 81 Gate_Ctrl sets U506A the next rising edge of the frequency source sets U508A high and the second rising edge sets U509A Freq_Start high Freq_Start is selected as the start to the time interval counter by U502 The Q of U509A also asserts Freq_Gate to allow the cycles of the frequency source to be counted until Freq_Stop is asserted The falling edge of the Gate_Ctrl bit sets U506B U508B and U509B are used to generate a Freq_Stop bit which is synchronous with the second rising edge of the frequency source after Gate_Ctrl goes low Freq_Stop is selected as the stop input to the time interval counter by U503 and is used to turn off the Freq_Gate bit to stop the cycle counter for the frequency input To measure a single cycle of the input source Int_Arm is asserted so that U506A amp B will be asserted immediately after the LOAD pulse is removed The first rising edge of the frequency source will set U508A and remove the reset to the U508B The next rising edge will set U509A the Freq_Start bit and remove the reset from U509B The third rising edge will set U509B the Freq_Stop bit The time between Freq_Start and Freq_Stop is equal to one cycle of the frequency input source To externally gate the bit Int_Gaten is set low allowing the discriminated EXT input Cmp3 to pass to the XOR gate U430C The Gate_Ctrl bit is now used to control the polarity of the EXT input which is to arm the unit Th
112. dividE by O Denominator 0 in ratio measurement SR620 Universal Time Interval Counter 58 _ Troubleshooting Tips Error Indicators STOPLED No Stop within 20 s of Start this may not be an error the LED is just a warning to indicate that the time interval is large Blink indicates B input autolevel attempt STARTLED No Start within 20 s of Stop TIME this may not be an error the LED is just a warning to indicate that the time interval is large Blink indicates A input autolevel attempt CLOCKLED Unit warming up or Ext timebase error See cAL CONFIG menu for timebase selection WRONG VALUE Verify the setting of the instrument by reading each front panel LED Is the REL set Are a very large number of samples specified Is the AUTO LED in the SAMPLE SIZE section turned ON Are the inputs terminated correctly Have the slope threshold and input coupling been set correctly Are there multiple edges on your input due to cable reflections To gain confidence that the instrument is working correctly try measuring the WIDTH FREQ and PERIOD of the REF Refer to the Quick Start instructions for step by step details To verify that the input section is working use the 1 kHz REF OUT set to TTL level to supply a signal to the A or B input and measure WIDTH tr tf FREQuency and PERiod Measure the length of a cable in the TIME MODE by connecting it between the REF OUT and the B input Select REF as the START SOUR
113. e 0x2105 set mode for dma input count 8 samples number of bytes set up TIC sprintf cmd BDMP d samples set binary dump mode of n samples TxGpib sr620 cmd send command to TIC TalkGpib sr620 make TIC a talker dma2 amp status amp mode amp count data amp seg read data via DMA StatCheck sr620 check status get mode so we ll know which conversion factor to use TxGpib sr620 MODE EXPD GetGpib sr620 read answer sscanf recv d d amp tmode amp texpd skip semicolon separator convert data and print both binary and converted form Convert tmode texpd samples printf n data n for i 0 i lt samples i printf 2x 2x 2x 2x converted 16 15IE s n data 4 i 3 data 4 i 2 data 4 i 1 data 4 i fdata i units tmode kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk x void Convert int mode int expd int samples int i j sign unsigned int words 4 static double factors 1 05963812934E 14 1 05963812934E 14 1 05963812934E 14 1 24900090270331E 9 1 05963812934E 14 8 3819032E 8 00390625 conversion factors for i 0 i lt samples i sign 0 fdata i 0 0 get 8 data bytes 4 2 bytes each for j 0 j lt 4 j words j data 4 i j if int words 3 lt 0 if answer lt 0 convert to magnitude and sign sign 1 sign of answer
114. e prompts gt and gt to indicate that a command was either processed correctly or contained errors The RS232 echo mode is good way to become familiar with the commands that the SR620 expects and the values that it will return When the unit is controlled by a computer the echo feature should be turned OFF Front Panel LEDs and data window To assist in programming the SR620 has 3 front panel status LEDs The ACT LED flashes whenever a character is received or sent over either interface The ERR LED flashes when an error has been detected such as an illegal command or parameter out of range The REM LED is lit whenever the SR620 is in a remote state front panel locked out To help find program errors the SR620 has an input data window which displays the data received over either the GPIB or RS232 interfaces This window is the first menu line in the CTRL submenu and displays the received data in hexadecimal format One may scroll back and forth through the last 256 characters received using the SCALE up down arrow keys A decimal point indicates the most recently received character Command Syntax Communications with the SR620 use ASCII characters Commands may be in either UPPER or lower case and may contain any number of embedded space characters A command to the SR620 consists of a four character command mnemonic arguments if necessary and a command terminator The terminator may be either a carriage return lt cr
115. e SR620 will compute and display statistics for sample sizes of one to one million The mean standard deviation or Allan variance minimum and maximum deviations may be displayed Statistics are available for all modes of operation Displayed values may be offset by the REL for measurements relative to a previous mean value Scope Displays and Hardcopy The SR620 can display histograms and strip charts on any xy scope Histograms show the distribution of values within a group of measurements Strip charts of the previous 250 mean values or deviations show data trends Hardcopy of scope displays may be made to printers or plotters via rear panel Centronics RS232 or GPIB ports Reference Output The front panel REF OUT provides a precision 1KHZ square wave at TTL or ECL levels This source may be used for calibration and is a convienent trigger for many types of measurements DVM s and DAC Outputs Two rear panel DVM inputs allow dc voltage measurements with 0 3 accuracy on 2 or 20 V full scale ranges The inputs may be displayed on the front panel or read via the RS232 or GPIB interfaces Two DAC outputs default to output voltages proportional to the mean and jitter readings to drive analog strip chart recorders The DAC output voltages may also be set or scanned from the front panel of through one of the computer interfaces Computer Interfaces Both GPIB and RS232 interfaces allow complete control of the instrument A fas
116. e adjusted by adjusting the channel A and B trigger knobs Setting the knobs for OV or to autolevel will set the sensitivity to maximum Setting the knobs to 5V will reduce the sensitivity SR620 Universal Time Interval Counter 10 Front Panel Operation to about 200mV rms Both positive and negative settings of the knob have the same effect The sensitivity adjustment is useful because at maximum sensitivity the prescalers will self oscillate with no signal input With an input however this is not a problem but by reducing the sensitivity slightly these oscillations will disappear INPUT COUPLING The A and B inputs may be either AC or DC coupled by pressing the AC DC button The coupling is independent of the input termination impedance The EXT input is always DC coupled REFERENCE OUTPUT The front panel REF output puts out a 1kHz 50 duty cycle square wave synchronized to the SR620 s internal 10MHz clock This output may provide 4V into high impedance or 2V into 50 Ohms or ECL levels into 50 Ohms An example of the use of this output is to set the mode to measure the time from REF to B If a cable is then connected from the REF output to B the cable delay may be directly measured SR620 Universal Time Interval Counter TIMEBASE INPUT AND OUTPUT A rear panel BNC outputs the SR620 s 10MHz clock This output supplies approximately 1V pk pk into a 50 ohm load Another BNC allows the input of a 5 or 10 MHz external timebase
117. e frequency gate starts when U506A is set by the rising edge of the non inverted output of U430C and the gate is terminated by the rising edge of the inverted output of U430C The bit Par_Hoff is high The synchronization of the Freq_Start and Freq_Stop bit works as described above for internal gating Regardless of gate width at least one cycle of the input will always be measured If Fast_Per is low then the first stage of re synchronization is skipped as U506A and U506B will be set when the Load pulse is terminated which will cause U508A and U508B to be set In this case the first rising edge of the selected frequency source will set U509A the Start and the second edge will set U509B the Stop This mode is not used EVENT GATING Sheet 9 of 16 There are three modes of generating a gate for event counting fixed gates from 1 us to 1 s delayed scanning gates from an external trigger and external gating The event gate is open from the time U506A is set until U506B is set The or gate U507C forms the Event Gate which enables the event counters via the multiplexer U504 For internal gates Int_Gaten is set high and the gate is controlled by Gate_Ctrl from the 8254 counter timers on sheet 6 of 16 The counter timers may provide fixed gates or gates which may be delayed or scanned relative to an external trigger For external gates the Par_Hoff bit is set high and the the discriminated output of the EXTernal
118. e in the fuse holder voltage card position and fuse value Disconnect the power cord open the fuse holder cover door and rotate the fuse pull lever to remove the fuse Remove the small printed circuit board and select the operating voltage by orienting the printed circuit board to position the desired voltage to be visible when pushed firmly into its slot Rotate the fuse pull lever back into its normal position and insert the correct fuse into the fuse holder LINE FUSE Verify that the correct line fuse is installed before connecting the line cord For 100V 120V use a 1 Amp fuse and for 220V 240V use a 1 2 Amp fuse LINE CORD The SR620 has a detachable three wire power cord for connection to the power source and to a protective ground The exposed metal parts of the instrument are connected to the outlet ground to protect against electrical shock Always use an outlet which has a properly connected protective ground CONNECTION TO OTHER INSTRUMENTS All front panel BNC shields are connected to the chassis ground and to the power outlet ground via the power cord Do not apply any voltage to either the shields or to the outputs The outputs are not protected against connection to any potential other than ground SR620 Universal Time Interval Counter vi Safety and Preparation for Use Symbols you may find on SRS products a Alternating current Caution risk of electric shock e Frame or chassis terminal A Caution
119. e is 32 6 Hz SR620 Universal Time Interval Counter Front Panel Operation 9 SETTING THE INPUTS A GATE tric per _TAIG sran My LEVEL LEVEL ACT seu a CU za LOGIC ON STBY a A 7 m Co Gel ear on MAN TERM ACDC INPUT LEVEL REF OUT EXT A e 2 IMQ IMQ i XY NS Ys A SETTING TRIGGER LEVELS SETTING TRIGGER SLOPES The trigger levels are set by rotating the trigger level adjust knobs These knobs may have a full scale range of 5 00V 2 50V or 1 25V The full scale range is set in the CONFIGURATION menu see that section of the manual for details In all cases the trigger level resolution is 10mV and the actual level may be displayed on the front panel The trigger inputs have about 40mV of hysteresis and the trigger levels are corrected for this hysteresis so that the inputs will trigger at the selected voltage independent of the selected trigger slope The LED s above the trigger knobs will flash when the input comparator triggers The A and B inputs may also be set to autolevel by rotating the knobs completely counter clockwise The AUTO LED under the knob will come on and the trigger threshold will automatically be set to the midpoint of the signal Autolevel will work for a signal faster than about 10Hz and a duty cycle greater than about 0 0001 The autolevel circuit will not change the trigger level until the input stops triggering for mor
120. e or negative time interval may be measured There is unfortunately some ambiguity to this method of arming For periodic inputs there is no way for the instrument to know if the desired time interval should be measured from the Start to the previous Stop or to the next Stop For example if the Start SR620 Universal Time Interval Counter and Stop are both 1 KHz square waves with the Stop edge following the Start edge by 1 uS then the unit will report a Time interval of either 1 us or 999 us In the TIME and TIME COMPLEMENT modes the start and stop inputs are armed by parity that is the reception of either a Start Stop pair or a Stop Start pair of pulses By changing between these two modes one may choose to measure either the time from Stop to the next Start or Start to the next Stop Since the parity of the input signals is randomly determined at power up there is no way to specify which arming mode will correspond to which measurement But by changing between these modes both measurements may always be obtained TIME Time Arming Aly At a Alternately one may arm a Time measurement with a signal applied to the Ext input in which case the measurement that is made Start to Stop or Stop to Start is determined only by the relationship of the Ext input to the Start and Stop signals TIME Time External Arming At je gt GATE eee The EXT input requires about 10 ns setup prior to the Start or Stop
121. e than 1 2 second Then it will try to reset the trigger level to a new value The red LEDs behind the words START and STOP will flash each time the autolevel circuit tries to adjust the trigger threshold NOTE in width and rise fall time modes which use only one input the A trigger knob sets the start trigger voltage and the B trigger knob sets the stop trigger voltage The A and B inputs can be set to trigger on either a rising or falling edge by pressing the SLOPE buttons The EXT input can be set to rising edge or falling edge by pressing the LOGIC button If the EXT input is being used to supply a gate pulse the SR620 will use the time above threshold as the gate if POSitive logic is selected and the time below threshold as the gate if NEGative logic is selected INPUT TERMINATION The EXT A and B input may all be terminated in either 1MOhm or 50 Ohms by pressing the INPUT or TERM buttons If the inputs are terminated in 50 ohms and the input signal exceeds 6V peak the 50 Ohm terminator will automatically be removed to prevent damage to the terminator When this overload condition occurs the 50 ohm LED will flash UHF PRESCALERS In frequency and period modes the input signal may be fed to the SR620 s UHF prescalers to measure signals between 40MHz and 1 3GHz To engage the prescalers press the INPUT button for the desired channel repeatedly until the UHF LED comes on The sensitivity of the prescalers may b
122. ed The internal 1kHz REF output may be selected in cases where the front panel REF out will be used to trigger an event and the event will provide a Stop pulse to the B input A simple example of this would be the measurement of cable lengths The length of a cable may be measured by selecting REF as the Start source and connecting the cable between the REF output and the B input Time Arming Mode Function When REF is used as the Start source the rising edge of REF is used when a positive slope is selected for the A input and the falling edge is used when a negative slope is set In this case the threshold knob above the A input has no effect on operation TIME INTERVAL ARMING There are several arming modes for Time interval measurements The arming mode controls when the instrument will be ready to take a sample Start and Stop pulses are ignored when the instrument is not armed The ARM LED will turn on when the unit is armed The SR620 remains busy for about 800us after receiving a Start Stop pair and may not be rearmed during this time TIME MEASUREMENTS 1ns to 1000s In TIME arming the Start input is armed as soon as the instrument is ready and Stop is armed when a Start is received In this mode only a positive or zero time interval may be measured TIME Time Arming In TIME EXTERNAL mode the Start input is enabled by the GATE and Stop is armed by Start A delay from an EXT input may be set or scann
123. ed in the CONFIG menu otherwise the EXT input will be the trigger TIME Stari arms automatically Stop is armed by Start TIME EXTERNAL Start is armed by EXT input Stop armed by Start TIME EXTERNAL STOP HOLDOFF Start is armed by leading edge of EXT input and the Stop is armed by the trailing edge TIME Starts and Stops are armed by Start Stop pair TIME COMPLEMENT TIME EXTERNAL Starts and Stops are armed by Stop Start pair Starts and Stops are armed by EXT input SR620 Universal Time Interval Counter 12 Sample Arming TIME Time External Arming jo TIME EXTERNAL with HOLDOFF is similar except that Stops are not enabled until the trailing edge of the EXT input A particular Stop pulse may be selected to end the time interval by using the EXT input to inhibit or holdoff the Stop input An example of this might be measuring the time from the index mark on a hard disk drive to a particular data bit By adjusting the holdoff time one could measure the time to any data bit instead of just the first one The trigger may be delayed or scanned from an EXT trigger input by setting SCAN parameters in the CONFIG menu A blinking EXT LED indicates that the EXT is used as a trigger for the delayed gate TIME Time External Arming with Stop Hold Off At GATE a TIME MEASUREMENTS 1000s lt t lt 1000s In all of the TIME modes Starts and Stops are armed simultaneously and so either a positiv
124. efaced by d or Allan variance display prefaced by A The statistic that is used is set in the CONFIGURATION MENU MAX displays the maximum sample found in this measurement If the display is prefaced by r then a relative reading is displayed and the value displayed is the max minus the REL MIN displays the minimum sample found in this measurement If the display is prefaced by r then a relative reading is displayed and the value displayed is the min minus the REL TRIG displays the trigger level set by the EXT A and B trigger knobs The full scale range of the knobs may be set in the CONFIGURATION MENU DVM displays the voltage values at the rear panel DVM inputs Pressing both the up and down arrow keys together toggles the x1000 expand on and off in frequency and period mode In frequency mode the x1000 expand moves the decimal point 3 places to the left and displays frequencies with nHz resolution The maximum frequency measurable in this mode is 1 MHz In period mode the x1000 expand moves the decimal point 3 places to the left and displays periods with fs SR620 Universal Time Interval Counter 6 Front Panel Operation resolution The maximum period measurable in this mode is 1 s In both period and frequency modes the statistical data is displayed with the number of significant digits allowed by the SR620 s resolution Using longer gate times increases the resolution GRAPHICS OUTPUTS In addition
125. eference the data memory will generate a port strobe to place data on the processor s data bus The seven LSB s from the Tick counter are read by U201 This counter is called the Tick counter because it usually counts the clock cycles of the 90 MHz timebase It may also be used to count events when in the COUNT Mode The seven LSB s from the CYCLE counter are read by U202 This counter is called the CYCLE counter because it usually counts the number of cycles of an input when the unit is in the FREQUENCY PERIOD or PHASE Modes Key presses may be detected as part of the LED display refresh A key press will connect a strobe line to one of the four input bits Kbrd_ 0 3 which may be read at the input port U203 If there are no key presses all of the Kbrd lines will be low The of input bits to U203 are Print_Err Detects printer error Neg_Time Indicates a Stop before Start DTR Low if RS232 device is ready Cal_En Jumper high to enable calibration DISPLAY CONTROL OUTPUT PORTS Sheet 4 of 16 U204 though U208 are octal latches 74HCT374 which latch the data bus contents on the rising edge of the port strobe Latched bits perform a variety of control functions within the instrument and are used to control the front panel LED displays and lamps as well as provide strobes to read key press data U204 selects two digits and ten LED s for refresh Only one of the eight bits is strobed low at a time saturating one of the trans
126. en the measured value and actual value of the signal being measured The error in a measurement is of primary concern when the absolute value of the parameter being measured is important Error consists of the random factors mentioned above and systematic uncertainties in the measurement Systematic uncertainties include timebase aging trigger level error insertion delay etc Systematic errors may always be measured and subtracted from subsequent measurements to reduce the error The SR620 s absolute error is typically less than 0 5ns for time interval measurements less than 1ms DIFFERENTIAL NON LINEARITY Absolute error is of interest in determining how far a value is from the actual value Often only the relative accuracy the difference between two measurements is important Differential non linearity is a measurement of the relative accuracy of a measurement and is specified as the maximum time error for any given relative measurement The SR620 s differential non linearity is typically 50ps That means if the time interval is changed by some amount the SR620 will report that change to within 50ps of that change Graphs 1 and 2 show the SR620 s typical differential non linearity as a function of time interval Graph 1 shows the non linearity over the time range of O to 11ns The deviations are due to the residual non linearity of the time to amplitude converters This curve repeats every 11 11ns the period of the time to amplitude converters Gr
127. enerator to the SR620 s B input and measure the same group of frequencies Record the results 6 Attach the rf generator s reference input to the SR620 s 10MHz output 7 Attach the generator s rf output to the SR620 s A input Terminate the A input into 50 ohms SR620 Universal Time Interval Counter 64 Performance Test Set the generator to 100 MHz and the output level to 2dBm Measure the frequency Set the output level to 1dBm and the frequency to 300MHz Measure the frequency The frequencies should read setting Frequency Reading 100MHz 100MHz 10 Hz 300MHz 300MHz 30 Hz Record the results 8 Set the SR620 s A input to UHF Set the A trigger level to 0 00V Set the generator to 300MHz with a 22dBm output level Measure the frequency Set the generator to 1 3GHz at an output level of 5dBm Measure the frequency The frequencies should read setting Frequency Reading 300MHz 300MHz 30 Hz 1 3GHz 1 3 GHz 130Hz Record the results 9 Repeat steps 7 and 8 for channel B Record the results Trigger Level Accuracy These tests confirm the accuracy of the SR620 s trigger level calibration specification 15mV 0 5 of setting 1 Attach the SR620 rear panel D A 0 output to the channel A input Also tee this signal to the voltmeter note noise from the voltmeter can produce false triggering of the SR620 A 1 10uF capacitor across the inputs of the voltmeter solves this problem 2 Set the S
128. error stop trigger level error 0 5 ns SR620 Universal Time Interval Counter Specification Guide ___27 FREQUENCY MODE In frequency mode the measurement resolution and error are given by N number of samples averaged frequency 25 ps short term stability x gate time y 2 x trigger jitter j Resolution t sc oonaovovm gate time N 00 ps Error resolution timebase error x frequency gate time x frequency The SR620 s typical single shot frequency resolution as a function of gate time is shown in Graph 5 The curves are for the standard oscillator the optional oven oscillator and an external high stability reference The input signal noise is negligible Typical Frequency Resolution vs Gate Time i q F 8 FA 10 B e d e S 3 a G A o 3 ia os 3 a m s 10 gt 2 re ii Opt Osc 5 a 310 e a xt Osc LL 104 er eer me 001 01 10 100 Gate Time s Graph 5 Typical frequency resolution as a function of gate time for the SR620 s three oscillator options PERIOD MODE In period mode the measurement resolution and error are given by N number of samples averaged period 25 ps short term stability x gate time 2 x trigger jitter Resolution gate time A N 100ps Error resolution timebase error x period gate time x period SR620 Universal Time Interval
129. ersal Time Interval Counter 62 Performance Test with 50 duty cycle The signal should go from OV to 4V Set the scope to 50 ohms The REF amplitude should now be 2V Set the REF output to ECL The signal should go from 1 8V to 0 8V with a 50 ohm termination EXT input 1 2 Set the REF output to TTL and connect it to the EXT input Adjust the EXT trigger knob and verify the triggering starts at about OV and stops at about 4V Set the EXT input to 50 ohms and verify that triggering now occurs between about 0 and V Set the REF output to ECL and verify that triggering occurs between about 1 8 and 0 8V A input 1 2 5 Set the REF output to TTL and connect it to the A input Adjust the A trigger knob and verify the triggering starts at about OV and stops at about 4V Set the A input to 50 ohms and verify that triggering now occurs between about 0 and V Set the REF output to ECL and verify that triggering occurs between about 1 8 and 0 8V Set the A input to AC and verify that triggering occurs between about 0 5 to 0 5 V B input 1 2 Set the REF output to TTL and connect it to the B input Adjust the B trigger knob and verify the triggering starts at about OV and stops at about 4V SR620 Universal Time Interval Counter 3 Set the B input to 50 ohms and verify that triggering now occurs between about 0 and 2V 4 Set the REF output to ECL and verify that t
130. et for 9600 baud 8 data bits no parity with hardware handshaking using the RS 232 control lines CTS and DTR this is the default of most plotters The RS 232 characteristics which are set in the control menu have no effect on the RS 232 port when used with a plotter If the GPIB port is specified for plotter output then the plotter s GPIB address must be set in the next line of the output menu The PRINTER PORT may be used as a general purpose digital I O port If a printer is to be used then this port should be setup as a printer port If the PRINTER PORT is not configured for a printer the message Print diSAbLEd will appear when Configuration Menus 19 the PRINT key is pressed When set as an output the port may be used as an 8 bit digital output port which is set by the controlling computer When set as an input port the controlling computer may read the eight bits asserted at the input port Printer Port Pin Assignments Pin Name Function 2 D1 Data bit I O 3 D2 Data bit I O 4 D3 Data bit I O 5 D4 Data bit I O 6 D5 Data bit I O 7 D6 Data bit I O 8 D7 Data bit I O 9 D8 Data bit I O 16 INIT Printer initialization 1 STROBE Byte output strobe 11 BUSY Printer busy 15 ERROR Printer error 14 AUTOFEED 5V via 1 kOhm 17 25 Chassis ground The ScALE line allows the DVM input ranges to be fixed to either 2 000 or 20 00 volts full scale The default condition allows the DVM s to auto scale The JitEr
131. et the source to B and attach the pulse generator to B 6 Set the slopes to and measure the rise time Adjust calbyte 48 until the answer reads 0 7 Set the slopes to and measure the fall time Adjust calbyte 49 until the answer reads 0 Width Mode 1 Set the mode to width arming to time Set both A and B thresholds to the midpoint of the input signal SR620 Universal Time Interval Counter 2 Setthe source toA 3 Attach the non inverting power splitter output to A Set the A slope to and measure the width Write this down as W1 4 Set the A slope to and measure the width Write this down as W2 5 Attach the inverting power splitter output to B Set the A slope to and measure the width Write this down as W3 6 Set the A slope to and measure the width Write this down as W4 7 Measure the period of the A input using a 1s gate Write this down as T 8 Calculate the CHANGE to calbytes 41 and 42 as follows calbyte 41 change W1 W3 T 2 2 7126736111E 12 calbyte 42 change W2 W4 T 2 2 7126736111E 12 9 Repeat steps 1 8 with channel B to get the changes in calbytes 43 and 44 Frequency Period Phase and Count mode 1 These modes need no calibration D A Output Calibration Offset Calibration 1 Attach a precision better than 0 1 error dc voltmeter to D A 0 Select the Scn submenu of the configuration menus Go to the d a mode line and set D A 0 and D A 0 to D A
132. etermined mainly by the desired resolution and measurement speed A longer gate results in a higher resolution measurement with 11 digits obtainable in a one second sample The SR620 always adjusts the number of displayed digits to reflect the appropriate resolution depending on gate time The accuracy of frequency measurements is FREQUENCY PERIOD SIGNAL 2nd pulse after rising edge N cycles At GATE Freq N At 1tNt10 7 Period At N 5ns sts 1000s SR620 Universal Time Interval Counter determined by the accuracy of time interval measurements For very short gates the accuracy is determined by the 200ps time interval accuracy while for long gates the accuracy is limited by the accuracy of the timebase EXTERNAL gates may be applied to the EXT input and may range from 5ns to 1000s although the SR620 always measures for at least 1 input period regardless of the gate time The setup time for an external gate is about 10 ns Additionally the EXT input may be used to trigger any of the internal gates in this mode both the ext and the gate time LED will be on This is useful for example to synchronize a 0 1s gate to an external event Additionally gates of 1 us to 10 ms may be scanned using the SR620 s scanning facility These gates must be externally triggered The gate may either be fixed in time relative to the EXT input or may be automatically scanned at the end of a measurement of N samples If scanned the step
133. evice Clear universal command The present value of a particular parameter may be determined by querying the SR620 for its value A query is formed by appending a question mark to the command mnemonic and omitting the desired parameter from the command If multiple queries are sent on one command line separated by semicolons of course the answers will be returned in a single response line with the individual responses separated by semicolons The default response terminator that the SR620 sends with any answer to a query is carriage return linefeed lt cr gt lt lf gt on RS232 and linefeed plus EOI on GPIB The RS232 terminator may be changed using the ENDT command while the GPIB terminator is fixed All commands return integer results except as noted in individual command descriptions Examples of Command Formats TERM 1 1 lt lf gt Sets the A channel input impedence to 1 Mohm 2 parameters TERM 1 lt lf gt Queries the A input termination query of 2 parameter command IDN lt lf gt Queries the device identification query no parameters STRT lt lf gt Starts a measurement no parameters MODE 1 MODE lt lf gt Sets mode to width 1 then queries the mode Detailed Command List The four letter mnemonic in each command sequence specifies the command The rest of the SR620 Universal Time Interval Counter sequence consists of parameters Multiple parameters are separated by commas Parameters s
134. f the driver circuits are located on the main PCB sheet 4 of 16 The PCB is a double sided gold plated glass epoxy board The gold plating is required for long term reliability of the rubber keypad All of the LED s are refreshed for 2 ms with a 1 8 duty cycle One of the strobe lines StbO to Stb7 is held high to refresh a pair of seven segment displays and a column of 10 LED lamps The particular segments and lamps in the strobe column are turned on by grounding the cathode of the LEDs through a current limiting resistor on the main PCB During the refresh time for a particular strobe column the state of the four keyboard switches in the column by be read by the processor The pn diodes in the strobe lines prevent simultaneous key closures in different columns from affecting the display refresh SR620 Universal Time Interval Counter 86 Circuit Description SR620 Universal Time Interval Counter Parts List 87 SR620 Parts List Front Panel Parts List REF SRS PART VALUE DESCRIPTION D1 3 00012 306 GREEN LED Rectangular D2 3 00012 306 GREEN LED Rectangular D3 3 00012 306 GREEN LED Rectangular D4 3 00012 306 GREEN LED Rectangular D5 3 00012 306 GREEN LED Rectangular D6 3 00012 306 GREEN LED Rectangular D7 3 00012 306 GREEN LED Rectangular D8 3 00012 306 GREEN LED Rectangular D9 3 00012 306 GREEN LED Rectangular D 10 3 00004 301 1N4148 Diode D 11 3 00884 306 RED LED Rectangular D 12 3 00012 306 GREEN LED
135. gain and control the rear panel chart recorder outputs The D A output is multiplexed to the S H amps by the 1 8 analog multiplexer U808 which is controlled by four latched processor bits Dac_Mpx and Dac_Inh The outputs from the analog multiplexer are passed through 10 KOhm resistors to reduce switching noise UNREGULATED POWER SUPPLIES Sheet 13 of 16 CAUTION Unregulated voltages are present on the PCB whenever the instrument is attached to an ac power source whether or not the front panel power switch is on The front panel power switch is used to enable most of the voltage regulators in the unit This approach is used to provide power to the timebase oscillator even when the instrument is not in use A power entry module with RF line filter is used to configure the unit for 100 120 220 or 240 Vac The line filter reduces noise from the instrument and reduces the unit s susceptibility to line voltage noise A 130 Vac Metal Oxide Varistor MOV stunts the line voltage to reduce spikes and to protect the unit from 220 vac when configured for 110 vac Full wave bridge rectifiers are used to provide unregulated dc at 7V 9V 20V and at 4V A Schottky diode bridge is used for the high current 7V supplies in order to reduce rectifier losses SR620 Universal Time Interval Counter The comparator U901B provides a squarewave to synchronize the scope display refresh to the line frequency PO
136. had by asserting the Busrq bit at which time the Z80H U116 releases the data address and control lines to the RAM and sets Busak low allowing the Z8800 s address data and control line to access the RAM via U114 116 The Z80 which is clocked at 8 MHz by the crystal oscillator X102 is executing a short program which is also stored in the RAM which writes xy pairs to the two 8 bit D A s The program can refresh 3000 points 60 times a second This hardware configuration relies on the fortunate fact that the Z80 instruction Out C A places the contents of the C register on the lower eight bits of the address bus and the contents of the B register on the top eight bits of the address bus This allows the Z80 to write 16 bits of data simultaneously to the two D A converters The Z80 executes a halt instruction after refreshing the XY display The halt is ended by a Line_Cross interrupt which starts the next refresh cycle A wavering display is avoided by synchronizing the refresh to the line frequency The quad op amp U121 provides 10 24 and 5 0 Vdc references to the two DAC s and converts their current outputs to voltages Whenever the SR620 Universal Time Interval Counter Z80 is halted or has relinquished its bus to the Z8800 the beam is pulled off the screen by current injected via D127 COUNTER INPUT PORTS Sheet 4 of 16 U201 through U203 are used to read data into the processor Read instructions which r
137. he bit values correspond to those used by the normal mode setting command For example the AUTM command with parameter j 1 turns on automeasure mode and automeasure bit setup byte 1 bit 0 is 1 if automeasure is on position meaning parameter format instrument mode same as MODE command source same as SRCE command arming mode same as ARMM command gate multiplier same as front panel control 0 1E 4 1 2E 4 etc sample size 0 1 18 corresponding to 1 2 5 1046 display source same as DISP command graph source same as DGPH command setup byte 1 bits of byte are 0 auto measure on off 1 autoprint on off 2 rel on off 3 x1000 on off 4 arming parity time 5 jitter type Allan Std Dev 6 clock ext int 7 clock freq10MHz 5 MHz bits are 0 1 A B autolevel on 2 3 DVMO gain auto 0 20V 1 2V 2 4 5 A B prescaler enabled 6 7 DVM1 gain bits are 0 Ext terminator 1 Ext slope 2 A slope 3 A ac dc 4 B slope 5 B ac dc setup byte Abits are 0 1 A terminator 2 3 B terminator 4 5 print port mode histogram vert scale 0 1 corresponding to 1 2 5 histogram horiz scale 0 1 corresponding to 1 2 5 led display least significant digit ps uHz etc histogram bin number 0 0 corresponding to 1 2 5 10 mean graph vert scale same as histogram horiz scale jitter graph vert scale same as histogram horiz scale setup byte 5 bits are 0 4 plotter address 5 plot print 6 plot gpib rs232 setup byte 6
138. he clear window just below the fuse When the unit is plugged in and turned ON the unit s model number firmware version number and serial number will be briefly displayed Then the message SELF TEST PASS should be briefly displayed If the unit displays no sensible message the cold boot procedure may fix the problem To do a cold boot turn the unit off Then while holding the RESET button in the SAMPLE SIZE section down turn the unit ON This procedure initializes the RAM and recalls all factory calibration values The Autocal procedure should be run after the unit warms up See below If the message code error appears it indicates that the SR620 s ROM has an error and the unit should be sent back for repair If a Test Error message appears you may be able to fix the problem with the unit s internal calibration routines Test Error Problem Lost Memory Cpu Error System RAM error Video RAM error 16 Count gate error 17 20 Channel 2 counter 18 19 Channel 1 counter oOoRW 32 Frequency gate 33 Excessive jitter 34 Insertion delay Freq 35 Insertion delay Time Any of these errors may be caused by a hardware failure which will require repair Test error 3 is usually self healing The instrument settings will be returned to their default values and factory calibration data will be recalled from ROM Test Error 3 will recur if the Lithium battery or RAM is defective Test errors 33 to 35
139. hen the measurement is complete The parameter j selects which statistic is to be returned j statistic 0 mean 1 jitter 2 max 3 min This command always returns the value of the next complete measurement Thus if a measurement is in progress the command will return the value of the present measurement when it is done not a new measurement It is recommended that automeasure be off when using this command to ensure that the result Programming Commands 33 returned is from the measurement desired Also no other queries should be sent between sending the MEAS query and reading its answer XALL The XALL query returns the values of the mean rel jitteri max and min of the last completed measurement These numbers are returned as one string with the individual numbers separated by commas The numbers are floating point values with up to 16 digits of precision XAVG The XAVG query returns the value of the mean of the last completed measurement The number returned is a floating point value with up to 16 digits of precision If the REL is set the number returned is the REL D value XJIT The XJIT query returns the value of the jitter of the last completed measurement The number returned is a floating point value with up to 16 digits of precision XMAX The XMAX query returns the value of the maximum of the last completed measurement The number returned is a floating point value with up to 16 digits of
140. his pulse train has a frequency spectrum which has equal amplitude components at 10 20 30 to about 100 MHz The matching network L307 and C328 resonates at 90 MHz to selectively couple the 90 MHz component into the emitter of the cascode amplifier Q309 The tuned collector load of Q309 L306 and C326 provides the input to the four pole crystal filter The crystal filter provides about 80 dB of selectivity for the 90 MHz signal which is discriminated by U305 a fast ECL comparator The output of this comparator is the timebase for all time interval measurements U312 buffers the 90 MHz clock to reduce crosstalk between various portions of the instrument The inductors in each tank circuit L307 306 303 and L304 are tuned to maximize the amplitude of the 90 MHz signal at TP 1 The 10 MHz square wave is converted to TTL levels by U309A to serve as the timebase for the internal gate generator The internal 10 MHz crystal oscillator either U301 or optional U303 may be phase locked to an external 5 or 10 MHz reference The external reference is ac coupled and buffered by Q308 to the Schmitt trigger U313A U313B C limit the output to ECL levels and drive one input to the ECL phase comparator U315 an MC12040 The control line Ext_5MHz is high to lock to an external 5 MHz reference When high U314A will divide by two providing 5 MHz to the other input of the phase comparator U315 To lock to an external 10 MHz reference Ext_5
141. hown in are optional or may be queried while those not in are required Commands that may be queried have a question mark in parentheses after the mnemonic Commands that may ONLY be queried have a after the mnemonic Commands that MAY NOT be queried have no Do not send or as part of the command Variable i is an integer that selects an input channel for the command i Channel O External input 1 A input 2 B input The variables j k l m and n are also integers The variable x is a real number All variables may be expressed in integer floating point or exponential formats ie the number five can be either 5 5 0 or 5E1 IMPORTANT NOTE ALL of the front panel settings to the left of the CONFIG button and the JITTER type Allan variance or standard deviation are properties of the present operating mode and are saved when the mode is changed Thus if the mode is changed the previous settings of these parameters in the new mode will automatically be set The programmer MUST be careful to set all relevant parameters each time the mode is changed to prevent conflicts between the presumed and actual states of the instrument Trigger Control Commands LEVL i x The LEVL command sets or reads the trigger threshold for channel i If the SR620 is in the autolevel mode this command will turn off the autolevel mode and set the desired threshold The trigger level set by the LEVL command will remain
142. hreshold Gain Calibration 1 Set the slope to and the threshold to 4 5V Set calbyte 6 7 5 to 1 Attach a precision dc source to input A Slowly increase the dc voltage from O until the trigger light flashes 2 The gain factor is dc voltage 4 5 3 Calculate the value of calbyte 6 7 5 as follows a If the gain is less than 1 multiply the gain factor by 65536 and round the answer even b If the gain factor is greater than or equal to 1 multiply the gain factor by 65536 and round the answer odd 4 Enter the new calbyte value Autolevel Offset Calibration For A and B only 1 With the input open turn the threshold knob to the autolevel position and read the trigger level 2 Divide the trigger level by 0 00488 3 Add this value to the calbyte Clock Oscillator Calibration Note Allow at least 1 hour warmup before adjusting the clock 1 Attach a scope probe to TP1 R305 in the right rear of the circuit board Set the scope to 50mV div and 20ns div 2 Adjust L303 L304 L306 L307 for maximum amplitude of the 90MHz clock signal 3 Run Autocal 4 Attach a precision 10MHz source to the A input and measure its frequency with a 1s gate Adjust calbyte 4 until the display reads exactly 10 0MHz The allowable range of calbyte 4 is 0 to 4095 all other numbers are set modulo 4096 If the frequency of the oven oscillator cannot be set with a calbyte in this range set the calbyte to midrange 2048 and Calibratio
143. ic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 NPO Capacitor Ceramic Disc 50V 10 SL Cap Monolythic Ceramic 50V 20 Z5U Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Cap Stacked Metal Film 50V 5 40 85c Capacitor Ceramic Disc 50V 10 SL SR620 Universal Time Interval Counter 90 Parts List REF SRS PART VALUE C 107 5 00021 501 82P C 115 5 00012 501 330P C 116 5 00012 501 330P C 117 5 00012 501 330P C 118 5 00012 501 330P C 119 5 00049 566 001U C 120 5 00012 501 330P C 121 5 00012 501 330P C 122 5 00127 524 2 2U C 123 5 00127 524 2 2U C 202 5 00127 524 2 2U C 210 5 00002 501 100P C 211 5 00002 501 100P C 212 5 00002 501 100P C 213 5 00127 524 2 2U C 222 5 00182 532 68P C 223 5 00023 529 1U C 224 5 00127 524 2 2U C 225 5 00023 529 1U C 226 5 00023 529 1U C 250 5 00011 501 27P C 251 5 00011 501 27P C 252 5 00023 529 1U C 301 5 00127 524 2 2U C 302 5 00127 524 2 2U C 303 5 00023 529 1U C 304 5 00023 529 1U C 305 5 00132 501 56P C 306 5 00023 529 1U C 311 5 00004 501 12P C 312 5 00004 501 12P C 313 5 00127 524 2 2U C 314 5 00127 524 2 2U C 323 5 00002 501 100P C 323A 5 00148 545 1000P C 324 5 00132 501 56P C 325 5 00002 501 100P C 326 5 00004 501 12P C 327 5 00023 529 1U C 328 5 00003 501 10P C
144. ich presets both flip flops in U244 and so releases the clear to U241B This allows U241B to run as a divide by two which provides 5 MHz to the clock input of 2 3 of U222 an 8254 counter timer This section of the 8254 is programmed to divide by 100 clocking the 3 3 of the 8254 at 50 kHz For gates shorter than 100 us the 2 3 of the 8254 will be programmed to divide by 5 The 3 3 of the 8254 is programmed as a software triggered one shot which sets the width of the internal gate The output of the 3 3 of the 8254 is resynchronized to the 50 kHz clock by U245B which provides the actual Gate_Cirl output This internally generated gate may be triggered by the front panel EXT input A delay from the EXT trigger to the opening of the gate may be set or scanned from the front panel configuration menu or via one of the computer interfaces The dual flip flop U244 is used to start the delay from EXT input To understand the circuit configuration for U244 notice that if either flip flop is clocked high then the Q output of U244A will be set high releasing the clear to the divide by two U241B Cmp3 is the comparator output for the Circuit Description 79 front panel EXT input The control signals Sel_Cmp3 and Sel_ Cmp3 are used to select the rising or falling edge of the EXT input to start the delay U244A will be clocked high by Cmp_3 going low if Sel_Cmp3 is set high and U244B will be clocked high by Cmp_3 going high if Sel_
145. ier is not equal to 1 see CONFIGURATION MENU and ARMING sections SR620 Universal Time Interval Counter Front Panel Operation 5 CHOOSING THE OUTPUT DISPLAY The SR620 can display statistical information about the measurement of N samples The SR620 computes and reports the mean standard deviation or root Allan variance minimum and maximum values seen during the measurement The equation for the statistical functions are given by mean gt M ta standard deviation root Allan variance SETTING THE FRONT PANEL DISPLAY The DISPLAY up and down arrow keys control what is displayed on the 16 digit LED display All of the statistical data is always calculated and may be viewed by scrolling through the displays The settings are MEAN displays the mean value of the measurement If the display is prefaced by r then a relative reading is displayed and the value displayed is the mean minus the REL REL displays the value of the REL The REL is set by pressing the SET button and is cleared by A oo III SCALE AUTO IAI PRINT CLR pressing the CLR button Normally the REL is set to the value of the mean when the SET button is pressed However the REL may be set to an arbitrary value using the ZOOM feature described in the GRAPHICS ZOOM section below Pressing the CLR button with the REL off clears the display JITTER displays either the standard deviation display pr
146. if j Set the trigger slope to 0 positive 1 negative Measurement Control Commands TRG Device trigger same as pushing start button ARMM j Sets the arming mode 0 time 1 time 2 1 period 3 0 01 s gate 4 0 1 s gate 5 1 0 s gate 6 ext trig time 7 ext trig time 8 ext gate trig holdoff 9 ext 1period 10 ext 0 01 s gate 11 ext 0 1 s gate 12 ext 1 0s gate AUTM j Sets resets autostart of measurements 0 off 1 on COMP Complements parity in time arming DREL j Sets clears the display REL 0 clear 1 set 2 clear REL and display 3 set rel to position of cursor GATE x Sets the value of the frequency period of count gate to x x may bebetween ims and 500s in a 1 2 5 sequence If x lt 0 a externally triggered gate of length x is set JTTR j Sets variance type to 0 std dev 1 Allan variance SR620 Universal Time Interval Counter xii__Abridged Command List MODE j SIZE j SRCE j STRT STOP Data Commands MEAS j XALL XAVG XJIT XMAX XMIN XREL x XHST j HSPT j SCAV j SCJT j BDMP j Scan Commands ANMD j DBEG j DSEN j DSTP x HOLD x SCAN SCEN j SCLR SLOC SCPT j VBEG j x VOUT j VSTP j x Graphics Control Commands AUTP j AUTS CURS j DGPH j GCLR Sets the instrument mode to 0 time 1 width 2 tr tf 3 freq 4 period 5 phase 6 count Sets the number of samples Sets the measurement sou
147. input is used to clock U506A and U506B The polarity of the external gate is controlled by the Gate_Ctrl bit COUNTING CHANNELS Sheet 9 of 16 There are two gated counting channels capable of 250 MHz operation and a count capacity of 1016 The gate and count inputs to the counters are selected by the multiplexer U504 The selected input clocks a D type flip flop This flip flop will count if the selected gate is high To count the D input must see the inverted output of the flip flop The XOR gate inverts the input to the D input when the gate is high The counter channel continues with another ECL flip flop conversion to TTL level and a 74F74 flip flop The output of the 74F74 flip flop is passed to a 74HC191 4 bit counter sheet 6 of 16 and on to the counter inputs of the central processor When counting events the top counter counts the Start_Mpx output the bottom counter counts the Stop_Mpx output and both counters are gated by the Event_Gate In all other modes of operation the top counter counts the 90MHz_C ticks and is gated by the Time_Gate and the bottom counter counts the output of the frequency source multiplexer U501 to count cycles in the frequency mode and is gated by the Freq_Gate The ECL counters are reset by the Load pulse and the CMOS counters are reset by the Reload pulse Fast transition time TTL outputs which drive long lines have 82 Ohm series resistors on their outputs to improve the pul
148. istors in U210 or U211 Should the port strobe to U204 become inactive the one shot 2 2 U131 will disable the output drivers so that no LEDs will be damaged U206 and U207 s outputs are set low to turn on particular segments in the even and odd digits A Circuit Description 77 high bit from U208 will saturate a transistor in U209 lighting the corresponding lamp on the front panel The front panel displays and keyboard are interface to the main PCB via a 40 pin cable J201 Each digit is refreshed for 2 mS Because there are large current transients associated with the multiplexed displays a separate 5 supply and ground return are provided for the LED s FRONT END STATUS BITS Sheet 5 of 16 U233 allows the processor to read various status bits from the front end inputs These status bits are defined as follows Bit Name Function 0 Bad_Clk Cold oven or bad Ext timebase 1 Ovid_A Overload to A s 50 Ohm terminator 2 Ovid_B Overload to B s 50 Ohm terminator 3 Ovid_Ext Overload to Ext 50 Ohm terminator 4 Armed Ready to make a measurement 5 Cmp_3ttl Flag for Ext Trig LED 6 Trig_2 Flag for B s Trig LED 7 Trig_1 Flag for A s Trig LED The last four bits in the above table are latched by U231 and U232 Three of the bits are converted from ECL to TTL levels by U230 All of the flags may be set with very short pulses 3 ns and the flags are cleared after reading when Flagclr is strobed by the processor FRONT
149. ity bit definition must be set in the ctrL section of the CONFIG menu The SR620 always sends two stop bits and will correctly receive data sent with either one or two stop bits When connecting to a PC use a standard PC serial cable not a null modem cable The SR620 is a DCE Data Communications Equipment device and so should be connected with a straight cable to a DTE device Data Terminal Equipment The minimum cable will pass pins 2 3 and 7 For hardware handshaking pins 5 and 20 CTS and DTR should be passed Occasionally pins 6 and 8 DSR and CD will be needed these lines are always asserted by the SR620 There are several software problems which may occur when using the RS 232 interface 1 You have sent the wrong command to ask for data from the SR620 Your program may wait forever for a response which will not come This may not be your fault we have seen Microsoft s Interpreted Basic on an IBM PC occasionally send a curly bracket ASCII 253 when it was suppose to have sent a carriage return ASCII 13 2 Your computer s baud rate was changed by a previous program and no longer matches the baud rate set for the SR620 Good programming practice requires that you set the computer s baud rate at the start of each application program 3 The initial command sent to the SR620 was invalid due to a garbage character left in the SR620 s command queue from power up or the first character in your computers RS
150. k 0 the selected channel is set to autorange if k 1 the selected channel is set to 20V full scale and if k 2 the selected channel is set to 2V full scale VOLT j The VOLT query reads the value of the selected input channel 0 or 1 Values outside the fullscale range indicate an overload condition Interface Control Commands RST The RST common command resets the SR620 to its default configurations It is the same as holding down clr rel at power on All modes are set to their default conditions IDN The IDN common query returns the SR620 s device configuration This string is in the format StanfordResearchSystems SR620 serial number version number Where serial number is the five digit serial number of the particular unit and version number is the 3 digit firmware version number OPC The OPC operation complete common command query is a synchronization command designed to simplify the coordination of commands that take a finite time to complete The OPC common command sets a bit in a status byte when all in progress measurements scans prints are complete The OPC common query returns the value 1 when all in progress measurements scans prints are complete An example of the use of this command would be to ensure that the present measurement is finished before the answer is read The command line STRT OPC would start a measurement and set a status bit when it was done Thus by polling
151. kkkkkkkkkkkkkk void TxGpib address command transmit command to address int address char command char t_string 150 int result result sprintf t_string UNT UNL MTA LISTEN d DATA s END address command transmit amp status t_string StatCheck address SR620 Universal Time Interval Counter Programming Examples ___55 kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk void GetGpib address get an answer from device at address int address char r_string 40 temp 80 sprintf r_string UNT UNL MLA TALK d address transmit amp status r_string StatCheck address strcpy temp receive amp status amp length temp StatCheck address strcpy recv temp kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk x void StatCheck address check the gpib status and exit if error int address if status 0 printf Error at device d status d address status exit 0 SR620 Universal Time Interval Counter 56 Programming Examples SR620 Universal Time Interval Counter Troubleshooting Tips _57 TROUBLESHOOTING To start make sure that the power entry module on the rear panel is set for the ac line voltage for your area that the correct fuse is installed and that the line cord is inserted all the way into the power entry module The selected line voltage may be seen through t
152. l Calculation time The calculation time occurs only after N measurements are completed and varies from zero N 1 no graphics binary responses to 5 ms N 1 no graphics to 10 ms display mean or std dev to 60 ms display histogram Frequency Range 0 001 Hz to 300 MHz via comparator inputs 40 MHz to 1 3 GHz via internal UHF prescalers RATIO A B range 10 to 103 Error lt 100ps typ 350 ps max Gate Timebase Error x Frequency Gates External 1 period 1ms to 500s in 1 2 5 sequence Gates may be externally triggered with no delay Gates may be delayed relative to an EXTernal trigger The delay from trigger may be set from 1 to 50 000 gate widths Display 16 digit fixed point with LSD Freq x 4ps Gate 1 uHz max resolution 1 nHz with x1000 for frequencies lt 1 MHz Period Range O to 1000 seconds RATIO A B range 10 9 to 103 Error lt 100 ps typ 350ps max Gate Timebase Error x Period Gates Same as frequency Display 16 digit fixed point with LSD 1 ps 1 fs with x1000 for periods lt 1 s Phase Phase 360 x Tb Ta Period A Range 180 to 180 degrees 0 to 100 MHz frequency Resolution 25ps x frequency x 360 0 001 degree SR620 Universal Time Interval Counter viii Specifications Gate Error Events Range Count Rate Gates Display Timebase Frequency Type Aging Allan Variance 1s typ Stability 0 50 C Settability External Inputs Threshold Accuracy Sensitivity
153. l the VCO First set the SR620 to measure FREQuency of the A input with a 0 01 s gate Select a SAMPLE SIZE of 1 Clear the DISPLAY REL and select MEAN for the scope display The rear panel output for D A 2 is connected to the VCO under test an the VCO output is connected to the A input In the CONFIG menu SET lines 1 through 6 as follows Configuration Menus 21 Scan Configuration Menu for D A Scan Example Line Display Function 1 ScAnEnA rEPEAt Enable repeated D A scans 2 ScAnPtsS 250 Take 250 point in each scan 3 hold 0 01 S Minimum hold time 4 dASrc chrtdAc D A 2 setup as D A 5 dA 1 000 D A 2 starts at 1 0 VDC 6 StEP 0 020 250 02V 5V scan Leave the CONFIG menu by pressing the RESET key in the SAMPLE SIZE section Then press and hold the START key to turn on the AUTO LED to initiate D A scanning After a few seconds press the AUTO key in the SCOPE AND CHART section to scale the scope display Note If the VCO stops running then the SR620 will stop taking data and everything stops Clearly you should select a VCO voltage ramp so that the oscillator never stops oscillating We chose D A 2 to control the VCO so that D A 1 would still be available for its default function to output a voltage proportional to the mean value frequency This will allow an XY chart recorder to plot the linearity curve of the VCO with the applied Wiis GMO lt eco ee IEEE IX 104 Y 4 96 Hz 32035316 MHz
154. low the PRINT button SCALING GRAPHS In histogram mode the vertical scale horizontal scale and number of bins may be adjusted In the stripchart modes the vertical scales may be adjusted The easiest way to scale the graphs is to press the AUTO button to autoscale the graph Autoscale will automatically adjust the scales so SR620 Universal Time Interval Counter that the data fits on the screen In histogram mode the actual scaling of the graph does not occur until the next measurement is complete The scale may also be adjusted manually Pressing the up and down arrow keys with the normal display on the 16 digit LEDs will adjust the vertical scale on the displayed graph In the histogram mode incrementing the vertical scale past the largest value 200 000 div will change the vertical scale to a log scale To view the scales on the LED display press the DISP button First the cursor position discussed below will be displayed Pressing the button again will display the vertical graph scales in the appropriate units In the histogram mode pressing the button again will display the horizontal scale and then the number of bins The scales may be adjusted using the up and down arrow keys When the REL is set the graphs are centered about the REL and thus very fine detail may be observed on a large number GRAPHICS CURSOR The displayed graphs have a moveable cursor that allows one to read the values of individual points o
155. m 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Parts List 101 REF SRS PART VALUE DESCRIPTION R 705 4 00039 401 120K Resistor Carbon Film 1 4W 5 R 706 4 00062 401 270 Resistor Carbon Film 1 4W 5 R 707 4 00138 407 10 0K Resistor Metal Film 1 8W 1 50PPM R 708 4 00021 401 1 0K Resistor Carbon Film 1 4W 5 R 709 4 00103 401 820 Resistor Carbon Film 1 4W 5 R 710 4 00138 407 10 0K Resistor Metal Film 1 8W 1 50PPM R 711 4 00192 407 49 9K Resistor Metal Film 1 8W 1 50PPM R 712 4 00072 401 330 Resistor Carbon Film 1 4W 5 R713 4 00034 401 10K Resistor Carbon Film 1 4W 5 R714 4 00472 407 806 Resistor Metal Film 1 8W 1 50PPM R715 4 00034 401 10K Resistor Carbon Film 1 4W 5 R 716 4 00473 407 11 0K Resistor Metal Film 1 8W 1 50PPM R 721 4 00080 401 47 Resistor Carbon Film 1 4W 5 R 722 4 00041 401 150 Resistor Carbon Film 1 4W 5 R 723 4 00090 401 560 Resistor Carbon Film 1 4W 5 R 724 4 00080 401 47 Resistor Carbon Film 1 4W 5 R 725 4 00039 401 120K Resistor Carbon Film 1 4W 5 R 726 4 00062 401 270 Resistor Carbon Film 1 4W 5 R 727 4 00138 407 10 0K Resistor Metal Film 1 8W 1 50PPM R 728 4 00021 401 1 0K Resistor Carbon Film 1 4W 5 R 729 4 00103 401 820 Resistor Carbon Film 1 4W 5 R 730 4 00138 407 10 0K Resistor Metal Film 1 8W 1 50PPM R 731 4 00192 407 49 9K Resistor Metal Film 1 8W 1 50PPM R 732 4 00072 401 330
156. m 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Re
157. may be corrected by the Autocal procedure To run this procedure press the SEL button in the CONFIG section to select CAL Press the SET button once choose Auto cAL Then press the START button in the SAMPLE SIZE section to begin the autocal procedure This procedure may not be started until the red CLOCK LED in the CONFIG section goes off otherwise a cAL Error 01 will result The autocal procedure takes about two minutes to run and ends with the message cAL donE the SR620 then returns to taking measurements If the UHF prescaler of channel A is selected when the unit is powered off and then on again the unit will display TEST ERROR 34 This error may be corrected by deselecting the UHF of channel A To run this procedure press input button of channel A until UHF is not highlighted Then turn the power off and on again Other cAL Errors flag hardware problems per the table below Cal Error Problem 1 Not warmed up 2 No trigger 3 7 Start TAC 19 23 Stop TAC The Start and Stop TAC s Time to Amplitude Converters are the circuits which perform the analog interpolation between the 90 MHz clock ticks The autocal procedure sets the gain and linearizes the transfer function of the TAC s COMMON OPERATIONAL PROBLEMS Error Messages Time interval has exceeded 1000 seconds or frequency exceeds 1 5 GHz in x1000 mode period gt 1S or countEr oFL frequency gt 1MHz rAtiooFL Ratio result exceeds 1000
158. mic Disc 50V 10 SL Capacitor Tantalum 50V 20 Rad Capacitor Tantalum 50V 20 Rad Capacitor Ceramic Disc 50V 10 SL Capacitor Monolyihic Ceramic COG 1 Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Cap Monolythic Ceramic 50V 20 Z5U Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Variable Misc Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Ceramic Disc 50V 10 SL Capacitor Mylar Poly 50V 5 Rad REF SRS PART VALUE C 407 5 00049 566 001U C 408 5 00011 501 27P C 409 5 00023 529 1U C 410 5 00023 529 1U C 411 5 00023 529 1U C 412 5 00023 529 1U C 413 5 00141 503 22U C 414 5 00009 501 24P C 415 5 00009 501 24P C 416 5 00023 529 1U C 421 5 00023 529 1U C 422 5 00104 530 3 5 20P C 423 5 00023 529 1U C 424 5 00023 529 1U C 425 5 00002 501 100P C 426 5 00062 513 0022U C 427 5 00049 566 001U C 428 5 00011 501 27P C 429 5 00023 529 1U C 430 5 00023 529 1U C 431 5 00023 529 1U C 432 5 00023 529 1U C 433 5 00141 503 22U C 434 5 00009 501 24P C 435 5 00009 501 24P C 436 5 00023 529 1U C 442 5 00104 530 3 5 20P C 446 5 0
159. mpile this program use the command FL AL FPi Gt40000 c bindump for the Gt option is needed to force the data array into the default data segment this is needed by the CEC software The resulting object file is then linked with FORT488 OBJ from CEC and the emulation math library which doesn t assume a math coprocessor 000000 0000000 program bindump the data from each point is stored in 4 consecutive location in the array data OO integer 2 seg count mode status samples integer 2 address tmode texpd integer 2 data 0 19999 real 8 fdata 0 4999 character 30 command character 40 rstring character dummy common data fdata call InitGpib 10 write A Enter number of samples lt cr gt to quit gt read BN 14 samples if samples gt 5000 goto 10 if samples eq 0 goto 11 C set mode for DMA input mode 16 2105 count 8 samples address 16 C set up TIC command 1 30 write command 100 samples 100 format BDMP 14 call TxGpib address command call TalkGpib address seg 1 C read data via dma SR620 Universal Time Interval Counter Programming Examples __ 49 call DMA2 seg data count mode status call StatCheck address status C get mode so we ll know which conversion factor to use command 1 30 command 1 11 MODE EXPD callTxGpib address command call GetGpib address rstring read rstring 101 tmode dummy texpd C skip semicolon separator 10
160. n Procedure 71 adjust the coarse adjustment screw on the oscillator until the frequency is correct Insertion Delay Calibration Start this procedure by running AutoCal on a well warmed up instrument Note If the calbytes calculated below are positive set the calbyte to that value If they are negative set them to 65536 abs value Use the scope histogram display to see measurement values when adjusting the Calbytes Time Mode 1 Set the mode to time arming to time source to A sample size to 1000 and the triggers to the midpoint of the input signals 2 Tee the output of the pulse generator to the A and B inputs with equal length cables Terminate the inputs with 50 Ohms 3 Set the A and B slopes to and measure the time interval Adjust calbyte 28 until the answer reads 0 4 Set the A and B slopes to and measure the time interval Adjust calbyte 31 until the answer reads 0 5 Attach the non inverting output of the power splitter to A and the inverting output to B 6 Set the A slope to and the B slope to and measure the time interval Adjust calbyte 29 until the answer reads 0 7 Set the A slope to and the B slope to and measure the time interval Adjust calbyte 30 until the answer reads 0 8 Set the Source to B 9 Set the A and B slopes to and measure the time interval Adjust calbyte 36 until the answer reads 0 10 Set the A and B slopes to and measure the time interval Adjust c
161. n power up if desired Sets reads the serial poll enable register Reads the serial poll register or just bit n of register Sets reads the error status enable register Reads the error status register or just bit n of register Reads the TIC status register or just bit n of register Sets reads the TIC status enable register Returns the complete setup in one string NOTE these commands are not needed during normal operation Reads the value of the time to amplitude converters Sets the printer handshake lines SR620 Universal Time Interval Counter xiv_ Abridged Command List POT j Reads the value of trigger pot j CAL Starts autocal and returns status when done TST Starts self test and returns status when done BYTE j k Reads sets linearization byte values WORD j k Reads sets cal words SR620 Universal Time Interval Counter Quick Start Use this procedure as a quick orientation to the instrument s features and capabilities If you encounter problems read the detailed discussions on operation or see the troubleshooting section Make sure that the correct line voltage has been selected on the rear panel power entry module With the unit s power switch on STBY hold the CLR key in the DISPLAY section down and turn the unit ON This will return all of the instrument settings to their default state The message SELF TEST PASS should briefly appear Note The fan will not run until the
162. n the screen The cursor is represented on screen by a dotted line The cursor is moved by pressing the DISP button to display the cursor position and using the up and down arrow keys to move it about The cursor x position is displayed on the LED display in the correct units of s Hz etc for the histogram display and measurement number for the stripcharts Both the x and y positions are displayed on the scope screen GRAPHICS ZOOM The SR620 has a feature which allows one to zoom in on any feature in a displayed histogram this feature also allows the REL to be set to any value desired First press the DISP button to display the cursor position Then move the cursor until it is at the desired position or the cursor value is the desired REL value if setting the REL Push the SET button This will set the REL to the cursor position Now adjust the graph horizontal scale to get the magnification desired If setting the REL value note that the amount that the cursor value changes for each press of the arrow keys is determined by the horizontal histogram scale and that the scale may have to be adjusted to get the REL value desired Front Panel Operation 7 HARDCOPY OUTPUT The displayed graph may be copied to either an Epson compatible graphics printer or a HP GL compatible plotter by pressing the PRINT key The SR620 will continue to take data while the hardcopy is being generated If a second print plot request is made b
163. nds 37 DISP j The DISP command set the front panel display The parameter j controls the display as shown in the following table j Display Codes Mean Value Rel Value Jitter Maximum Value Minimum Value Trigger Threshold DVM inputs oOnahon _Oo EXPD j The EXPD command sets the x1000 expand mode in frequency and period mode The parameter j 1 turns expand ON while j O turns expand OFF Rear Panel Control CLCK j The CLCK command sets the source of the 10MHz clock The parameter j 0 sets the clock source to internal while j 1 sets the source to external CLKF j The CLKF command sets the frequency that the SR620 expects at the external clock input The parameter j O sets a 10MHz external clock while j 1 sets a 5 MHz external clock PORT 7 j The PORT command sets or reads the value of the printer port when that port is configured as a general purpose I O port The parameter j 0 lt j lt 255 is the value sent to the port in decimal if it is an output If the port is configured as an output the strobe line is strobed low for about 10us every time a valid byte is set PRTM 7 j The PRTM command sets the mode of the printer port If j O the port is a printer port if j 1 the port is a general purpose input port and if j 2 the port is a general purpose digital output port RNGE jfk The RNGE command sets the input voltage range of DVM input j j 0 1 If
164. nitions for these bits is given in the table below Bit Name Function 0 Dac_Mpx0 DAC multiplexer LSB 1 Dac Mpxi DAC multiplexer middle bit 2 Dac_Mpx2 DAC multiplexer MSB 3 Dac _Inh High to inhibit multiplexer 4 Sel Cmp3 High to start delay on EXT rise 5 Int_Clk Low to use internal timebase 6 Ttl Ecl High for TTL REF output 7 Sel_ Cmp3 High to start delay on EXT fall There are 24 emitter coupled logic ECL level status bits available from three HC shift registers U237 U238 and U250 The outputs from these ICs swing between 0 7 vdc and 5 2 vdc Data from the processor s MSB is shifted serially into these registers by Eclshf and transferred to their outputs by the port strobe Rck The data clock and load bits are level shifted by the resistor networks N213 and N214 The 0 7 Vdc supply for the shift registers comes from a transistor in U239 These ECL level bits allow the processor to control the mode of the ECL circuits which do the fast measurements U237 and the LSB of U238 control SR620 Universal Time Interval Counter 78 Circuit Description the Frequency Start and Stop ECL multiplexers see sheet 9 of 16 These multiplexers select the signal sources to be measured U250 is used to enable the portions of the front end which are needed to do a particular measurement For example if the frequency of a slow signal on the A input is to be measured only comparator 1 will be enabled Cmp1_En is high all
165. offset adjust 11 12 13 Ext A B negative slope zero offset adjust 14 15 A B autolevel offset adjust 16 D A 0 zero offset adjust 17 D A 1 zero offset adjust 18 D A 0 gain adjust 19 D A 1 gain adjust 20 DVM input 0 20V range zero offset 21 DVM input 1 20V range zero offset 22 DVM 0 zero offset for 2V range 23 DVM 1 zero offset for 2V range 24 DVM 0 20V range gain adjust 25 DVM 1 20V range gain adjust 26 DVM 0 2V range gain adjust 27 DVM 1 2V range gain adjust 28 39 Insertion delay correction total correction base byte40 correction for inputs and slopes A B A B A B A B REF B REF B REF B REF B B A B A B A B A 40 Base insertion delay 41 45 Width insertion delay correction total correction base byte 40 correction for inputs and slopes A A B B REF 46 49 Tr tf insertion delay correction total correction base byte 40 correction for inputs and slopes A A B B 50 Freq period insertion delay 51 115 Start TAC linearization bytes 116 180 Stop TAC linearization bytes SR620 Universal Time Interval Counter 70 Calibration Procedure Note The AutoCal procedure automatically adjusts bytes 0 3 40 45 50 180 That is it automatically adjusts the start and stop TACs the TAC linearity the base time interval insertion delay the width of REF insertion delay correction and the freq period insertion delay Calibration Procedure Note Allow 1 2 hour warmup before c
166. olds may be set with 10 mV resolution The 350 MHz bandwidth of the inputs allows measurements of rise and fall times down to 1 ns Frequencies from 0 001 Hz to 1 3 GHz may be measured The SR620 will provide 11 digits of resolution when a one second gate is used Frequencies above 300 MHz may be measured on either input using the UHF prescalers NanoHertz resolution is available in the x1000 display mode Periods may be measured with femtosecond resolution Period measurements are done the same way as frequency measurements except the reciprocal of frequency is reported to the display The Phase between the signals on the A and B input may be measured with 0 001 resolution The phase shift between signals from 0 001 Hz to 100MHz may be measured The Count mode is used to count input transistions during a gate Count rates up to 300 MHz will be tallied Arming and Gating Each of these modes are supported with powerful arming and gating modes Time arming modes include Time Time External Time External with Stop Holdoff Time and Time External SR620 Universal Time Interval Counter Frequency gating modes include fixed gates of one period 0 01 s 0 1 s 1 s Externally triggered fixed gates External gates Externally triggered adjustable gates from 1 us to 10 ms Gates which are externally triggered may be delayed and scanned by 1 to 50 000 gate widths to allow transient frequency measurements Statistics Th
167. on Menus automeasure will automatically take a whole scan In the single scan mode automeasure will automatically be disabled at the end of the single scan Pressing the RESET button will reset and retake a single scan point and turning off automeasure will pause the scan A scan may be reset by pressing the CLR button in the graph section of the front panel When delay scans are enabled the function of the EXT gate arm input changes dramatically and so whenever the unit is first turned on scans will always be disabled The next line of the scan menu sets the number of points in the scan The maximum value is 250 points corresponding to the horizontal resolution of the scope display Scans with fewer points will of course be completed in less time Each point in the scan contains data from the number of points specified in the SAMPLE SIZE Line 3 allows the dwell time hoLd to be set The dwell takes place at the end of every scan point to allow time for the D A values and the signal source time to settle The default dwell time is 10 ms Longer dwells may be set if required by the system under test The dA Src line sets the source for the rear panel D A outputs dA Src The default setting for these outputs is chrt The default function of the D A outputs is as analog outputs to strip chart chrt recorders D A 1 outputs a voltage proportional the the MEAN value of the current measurement and D A 2 outputs a voltage
168. ors U907 and U908 can provide 15 vdc to the timebase Two status bits are also generated Drop_Out tells the processor that the 5 0 VDC supply has dropped below 4 6 vdc and Reset is asserted if the 5 vdc supply is below 4 4 vdc or has been below 4 4 Vdc in the previous 1 second The 24 Vdc brushless fan speed is controlled by the temperature in the box the warmer the box the faster the fan turns When cool the 6 mA drawn by R908 through R907 a 50 Ohm 40 C transition thermistor is not sufficient to turn on Q907 As the box warms above 40 C R907 becomes a high resistance and some portion of the full 6 mA can be drawn from the base of Q907 which turns on Q908 This proportional Circuit Description 85 temperature control can provide O to 26 Vdc to the fan Thermal control of the fan speed has several advantages including quieter operation longer fan life faster warm up and lower overall temperature coefficients for the instrument POWER SUPPLY BYPASS Sheet 15 of 16 The 60 bypass capacitors for the 5 5 2 2 and 15 Vdc power supplies are shown on this page These capacitors are distributed around the PCB they bypass portions of the power plane to the ground plane inside PCB layers Unused portions of IC s are also shown on this page FRONT PANEL DISPLAY PCB Sheet 16 of 16 The front panel display PCB holds 16 seven segment displays U1 16 75 LED lamps and 32 conductive rubber keys All o
169. other comparators and prescalers will be turned off as they are noise sources for this measurement The bits Trigi_Pol and Trig2_Pol are set so that the latches in U232 are set by the selected input signal polarity This ensures that the TRIG LED s will blink on the correct edge of the input signal The edge which is used for measurement is selected by the ECL multiplexers on sheet 9 of 16 The functions of the status bits provided by U238 are detailed in the table below Bit Name Function B Cnt f_ti High for COUNT mode C Int_Arm Low for internal arming D P_Time Low for positive time arming E P M_Time Low for time arming F Par Hoff Parity and hold off control More detail regarding the operation of these control lines is provided in the sections which describe the ECL arming and counting circuitry 1 kHz REFERENCE OUTPUT Sheet 6 of 16 A 1 000 KHz calibration signal is generated by dividing the 10 MHz clock by 2 in U241A and dividing the 5MHz by 5000 in 1 3 of U222 an 8254 counter timer The 1 kHz output from the 8254 is also used as a real time interrupt to the Z8800 to time certain housekeeping functions such as refreshing the front panel LED s The output of the 8254 is a square wave which is re sync ed to the 5 MHz clock by U245A a D type flip flop The output of the flip flop is translated to ECL by U550A and re sync ed to the 10 MHz clock by U311A an ECL D type flip flop The careful resynchronization is req
170. panied by a stop The output of U611A is delayed by a few nanoseconds to handle the case that starts and stops are coincident The bit Par Hoff is used to select the parity of the one bit counters which will clock U612A amp B to release the LOAD pulse If either U612A or B is clocked low their wire or ed Q output will set the D input to the start and stop latches high Changing the Par Hoff bit will allow the compliment period to be measured U612A amp B are preset by the Load pulse Circuit Description 83 There are three basic modes for external arming EXT Time EXT Time and EXT Time with Stop Holdoff In addition each of these modes may be used with delayed and scanning gates The arming criteria which applied in Time and Time also apply in EXTernal arming except that the Start_En and Stop_En are not set when the Load line goes low If positive logic is selected for the EXT input and the EXT Time with Stop Holdoff is selected then the rising edges of the EXT input will set Start En and the falling edge of the EXT input will set Stop En Note that stop pulses are inhibited until the falling edge of the EXT input If stop holdoff is not selected then the Par Hoff line is low and the Stop_En flip flop U506B will be set by U505B when Start_En occurs In this case stop pulses are not held off by the EXTernal input TIME INTEGRATORS Sheet 11 of 16 The time interval resolution of 4 ps is attained by measuring
171. pe divisions The scale is the same as the scope scales In the cases where zero is at the center of the scope screen the REL is set for example zero will correspond to 4 volts output The chart outputs may also be configured as general purpose D A outputs see CONFIGURATION MENU section EXAMPLES OF GRAPHS Number x 10 0 6 4 2 Width x 10 11 bins 25 Sample Histogram The graph scales are 20ps div in the horizontal direction and 10 div in the vertical The REL is 500 000023 us and is at the center of the graph This measurement has a mean value 6ps greater than the REL and a standard deviation of 9ps The cursor dotted line is at the REL and there are 46 events in that bin SR620 Universal Time Interval Counter 8 Front Panel Operation 4 hel 10 0223 X 67 Y R 1 635 i miel et ow ae ees Frequency x 40 Hz 3 3 ro 4 Sample mean value graph Each point corresponds to the mean value from one measurement The vertical scale is 10 Hz div The measurements are relative to a REL of 10 022176 kHz The REL is at the center of the graph The cursor dotted line shows that measurement number 67 was 1 635 kHz below the REL Frequency Variance x soi Hz ras 4 I Sample jitter stripchart This graph shows the jitter associated with each measurement above The vertical scale is 10 Hz div The cursor is at measurement number 165 and the jitter value ther
172. precision If the rel is set the number returned is the REL d value XMIN The XMIN query returns the value of the minimum of the last completed measurement The number returned is a floating point value with up to 16 digits of precision If the rel is set the number returned is the REL D value XREL x The XREL command sets the display REL to the value x The XREL query returns the value of the REL XHST j The XHST query returns section j j 0 to 9 of the histogram display as 4 byte binary integers least significant byte first Each section consists of the data for 25 histogram points 100 bytes total plus terminator There is no separator between successive points If the rs232 interface is being used an 8 bit data word must be chosen to correctly transmit this data The data returned is binned into 250 bins not the number set by the front panel This command allows one to rapidly read the entire contents of the histogram display If the histogram is blank the illegal numbars 0 are returned HSPT j The HSPT query returns the value of point j of the current histogram J has the range 1 to 250 If the histogram is blank this query returns the illegal value 9E20 SCAV j The SCAV query returns the value of point j of the mean graph or scan point j J has the range of 1 to 250 This query returns the illegal value 9E20 if the stripchart is blank has not reached point j or the scan has not reached point j
173. put of one of these amplifiers is selected by the analog multiplexers U802A amp B The selected signal is buffered by U801B which also amplifies the signal by about 10 if the switch U802D is closed The analog switch U802C samples the amplified output onto C805 The processor closes the S H switch for about 20 us prior to conversion Calibration bytes for offset and gain correction for both channels are stored in ROM and RAM AUTOLEVEL CIRCUITS Sheet 12 of 16 There are two autolevel circuits which output a voltage between the peak and minimum levels seen at the A and B inputs The circuit references will be given for the A input SR620 Universal Time Interval Counter 84 Circuit Description The peak input level is detected by Q801 and held on C832 The minimum input level is detected by Q802 and held by C831 Q801 and Q802 are biased by the 10 MOhm resistors R834 and R831 respectively The detected voltages are averaged and filtered by R832 R833 and C833 and buffered by the FET input op amp U809A DIGITAL TO ANALOG CONVERTER Sheet 12 of 16 A 12 bit D A converter U806 is used to provide analog voltages to the system The D A converter is referenced to the 5 00 vac reference from U906 The current output is converted to a voltage by the op amp U807B The voltage is amplified and offset by U807C to cover the range of 5 12 vdc The D A output is used to refresh several S H amplifiers to set input threshold conversion
174. r of the previous sampled signal U703D buffers the sampled voltage to the ADC converter The signal to the A D converter covers 2 3 of its 4096 bit range with a Start_Ck range of 11 11 ns implying a resolution of 4 ps bit To maintain an accuracy and jitter commensurate with this resolution it is necessary for the processor to perform some empirical linearity corrections to the Start_Ck and the Stop_Ck voltages The 7 us strobe to the sample and hold switch and the processor interrupt request Start_Int is generated by U704A a dual one shot The one shot is triggered by the Start pulse which is converted to TTL levels by U707A ANALOG TO DIGITAL CONVERTER Sheet 12 of 16 U805 is a 12 bit A D converter Each conversion takes about 100 us Referenced to the buffer amplifier s output U810A the A D has a full scale range of 5 V A conversion is initiated when the processor writes to the A D converter Before starting a conversion the processor selects the source with the 1 of 8 analog multiplexer U803 Three latched bits Adc_Mpx select the source The ADC s voltage reference is 5 00 vdc from U906 which serves as a voltage reference for the entire unit The A D converter can digitize the Start_Ck or Stop_Ck voltages the front panel threshold pot positions a selected rear panel DVM inputs or autolevel circuit voltages The isolated BNC s on the rear panel are buffered by the differential amplifiers U801C amp D The out
175. rbon Film 1 4W 5 SR620 Universal Time Interval Counter 100 Parts List REF SRS PART VALUE R 429 4 00465 405 330 R 430 4 00030 401 10 R 431 4 00027 401 1 5K R 433 4 00122 405 47 R 441 4 00021 401 1 0K R 443 4 00056 401 22 R 444 4 00428 407 562 R 445 4 00429 407 511 R 446 4 00021 401 1 0K R 447 4 00080 401 47 R 448 4 00030 401 10 R 449 4 00030 401 10 R 458 4 00081 401 470 R 461 4 00427 449 49 9 R 462 4 00021 401 1 0K R 463 4 00398 407 499K R 464 4 00398 407 499K R 471 4 00021 401 1 0K R 473 4 00056 401 22 R 474 4 00428 407 562 R 475 4 00429 407 511 R 476 4 00021 401 1 0K R 477 4 00080 401 47 R 478 4 00030 401 10 R 479 4 00030 401 10 R 480 4 00034 401 10K R 481 4 00034 401 10K R 482 4 00034 401 10K R 483 4 00034 401 10K R 484 4 00032 401 100K R 485 4 00032 401 100K R 486 4 00086 401 51 R 490 4 00048 401 2 2K R 491 4 00094 401 6 8K R 492 4 00048 401 2 2K R 493 4 00061 401 240K R 496 4 00032 401 100K R 497 4 00122 405 47 R 498 4 00031 401 100 R 499 4 00031 401 100 R 501 4 00086 401 51 R 502 4 00086 401 51 R 503 4 00031 401 100 R 504 4 00056 401 22 R 505 4 00056 401 22 R 550 4 00031 401 100 R 600 4 00072 401 330 R 701 4 00080 401 47 R 702 4 00041 401 150 R 703 4 00090 401 560 R 704 4 00080 401 47 SR620 Universal Time Interval Counter DESCRIPTION Resistor Carbon Film 1 8W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 8W 5 Resistor Car
176. rbon Film 1 4W 5 R 401 4 00427 449 49 9 Resistor Metal Film 1 2W 1 50ppm R 402 4 00086 401 51 Resistor Carbon Film 1 4W 5 R 403 4 00398 407 499K Resistor Metal Film 1 8W 1 50PPM R 404 4 00398 407 499K Resistor Metal Film 1 8W 1 50PPM R 405 4 00065 401 3 3K Resistor Carbon Film 1 4W 5 R 406 4 00034 401 10K Resistor Carbon Film 1 4W 5 R 407 4 00021 401 1 0K Resistor Carbon Film 1 4W 5 R 408 4 00027 401 1 5K Resistor Carbon Film 1 4W 5 R 409 4 00465 405 330 Resistor Carbon Film 1 8W 5 R 410 4 00030 401 10 Resistor Carbon Film 1 4W 5 R 411 4 00021 401 1 0K Resistor Carbon Film 1 4W 5 R 413 4 00056 401 22 Resistor Carbon Film 1 4W 5 R 414 4 00428 407 562 Resistor Metal Film 1 8W 1 50PPM R 415 4 00429 407 511 Resistor Metal Film 1 8W 1 50PPM R 416 4 00021 401 1 0K Resistor Carbon Film 1 4W 5 R 417 4 00080 401 47 Resistor Carbon Film 1 4W 5 R 418 4 00030 401 10 Resistor Carbon Film 1 4W 5 R 419 4 00030 401 10 Resistor Carbon Film 1 4W 5 R 421 4 00427 449 49 9 Resistor Metal Film 1 2W 1 50ppm R 422 4 00086 401 51 Resistor Carbon Film 1 4W 5 R 423 4 00398 407 499K Resistor Metal Film 1 8W 1 50PPM R 424 4 00398 407 499K Resistor Metal Film 1 8W 1 50PPM R 425 4 00065 401 3 3K Resistor Carbon Film 1 4W 5 R 426 4 00034 401 10K Resistor Carbon Film 1 4W 5 R 427 4 00021 401 1 0K Resistor Carbon Film 1 4W 5 R 428 4 00081 401 470 Resistor Ca
177. rce to 0 A 1 B 2 REF 3 ratio Same as pushing start button Same as pushing stop button Startts a measurement and returns the result when it is complete If j 0 the mean is returned j 1 returns the jitter j 2 returns the max and j 3 the min Returns mean rel jitter max min of a measurement Returns the mean of measurement Returns the jitter of a measurement Returns the max of a measurement Returns the min of a measurement Sets the value of the display rel to x Returns section j of the histogram display as 4 byte binary integers j 0 to 9 Return the value of the point n on the histogram j 1 to j 250 Returns 9E20 if graph is blank Returns the value of point n 1 250 of the mean stripchart or the value of scan point j returns 9E20 if the stripchart is blank or the scan has not reachedpoint j Returns the value of point n 1 250 of the jitter stripchart or the value of scan point j returns 9E20 if the stripchart is blank or the scan has not reached point j Binary dumps j points Sample size 1 Sets the DAC output mode of the mean and jitter DAC s to 0 chart chart 1 DAC chart 2 chart DAC 3 DAC DAC Sets the delay scan start position to 1 50000 step sizes after the external trigger Enables the internal delay scan 0 delay off 1 delay hold 2 delay scan Sets the delay scan step size to 1 2 5 x 10 3 4 5 6 1 x 10 is the maximum step size Sets the hold time between scan points from 0
178. rcuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Integrated Circuit Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg Thru hole Pkg nnn nnn nn nnn ni nnn nn nnn nnn nn nn nn nr i i nn Rn nj Parts List 105 SR620 Universal Time Interval Counter 106 Parts List REF SRS PART VALUE U 902 3 00088 340 LF353 U 903 3 00143 340 LM393 U 904 3 00088 340 LF353 U 905 3 00185 340 LM2901 U 906 3 00319 340 AD586JN U 907 3 00114 329 7815 U 909 3 00149 329 LM317T U 910 3 00141 329 LM337T U 912 3 00088 340 LF353 X 101 6 00046 620 20 000 MHZ X 102 6 00047 620 8 000 MHZ X 302 6 00040 620 90MHZ CF X 303 6 00040 620 90MHZ CF ZO 0 00014 002 6J
179. reciprocal frequency counter That is it measures frequency by measuring the time interval for an integer number of cycles of the input The frequency is then equal to number of cycles Measured Time Since there is no fraction of a cycle error as would be seen if the unit merely counted cycles in a fixed gate a frequency measurement can be made to 11 digits of resolution in one second For frequencies between O and 200MHz the SR620 s front end comparators may be directly used For frequencies between 200MHz and 1 3GHz the Ultra High Frequency UHF prescalers must be used The number of cycles used in the sample is determined by the GATE The instrument will always measure at least 1 period of the input Gates from 1ms to 500s or EXTernal gates may be selected from the front panel The actual gate time for the internal gates is the gate time set on the front panel multiplied by the gate scale set in the configuration menu Thus if one desired a 20s gate one would set the gate scale to 200 and the gate time to 0 1s 0 1s x 200 20s If the gate scale is not set to the default of 1 the gate time led on the front panel will blink Due to internal synchronization circuitry the frequency measurement starts on the 2nd input edge after the gate opens and ends on the second input edge after the gate closes Thus a frequency measurement always requires at least 2 complete cycles of the input waveform The choice of GATE mode is d
180. refer to accompanying documents Earth ground terminal o eem o o em SR620 Universal Time Interval Counter Specifications _ vii Specifications Functions Time Interval Pulse Width Rise and Fall Times Frequency Period Phase and Event Counting Measurement statistics mean min max standard deviation or Allan variance and graphics are available in all modes of operation Time Interval Time Width Rise and Fall Times Range 1000 to 1000 s in TIME mode 1 ns to 1000 s in all other modes Trigger Rate O to 100 MHz Least Significant Digit 4 ps single sample 1 ps with averaging Resolution 25 ps typ 50 ps max 2 0 2 ppb x Interval 2 N 1 2 rms 25 ps typ 50 ps max 2 0 05 ppb x Interval 2 N 1 2 rms Opt 01 Error lt 500ps typ 1 ns max Timebase Error x Interval trigger error lt 50ps typ 100ps max Timebase Error x Interval REL Arming Modes TIME Stop is armed by Start TIME EXT Ext arms Start TIME EXT HOFF Leading EXT edge arms Start trailing EXT edge arms Stop TIME Armed by Start Stop pair TIME CMPL Armed by Stop Start pair TIME EXT Armed by EXT input edge EXT arming may be internally delayed or scanned with respect to the EXT input in variable steps The step size may be set in a 1 2 5 sequence from 1 us to 10 ms The maximum delay is 50 000 steps Display 16 digit fixed point with 1 ps LSD Sample Rate For a sample size of N the total sample time is N x 800 us measured time interva
181. req_Stop from the frequency gating logic as the start and stop signals FREQUENCY GATES Sheet 9 of 16 The frequency gating circuitry is used to generate a start and a stop pulse for time interval measurement The start pulse Freq_Start occurs on the second transition of the selected source after the frequency sampling gate is opened the stop pulse Freq_Stop occurs on the second transition of the selected frequency source after the frequency gate is closed The circuit also generates Freq_Gate so that the number of cycles may be counted Dividing the number of cycles by the time interval gives the frequency If the signal Fast_Per is asserted then the Start pulse occurs on the FIRST transition of the selected source after the frequency sampling gate is opened the stop pulse occurs on the FIRST transition of the selected frequency source after the frequency gate is closed This allows the time between a single event pair to be measured This mode is not used There are four modes of gating a fixed gate of 1 us to 1s duration gates which may be delayed or scanned relative to and external trigger an external gate of arbitrary duration or gating to time a single period of the input waveform For internally generated gates the bit Int_Gaten is set high and the gate is controlled by the bit Gate_Ctrl The Gate_Citrl bit may provide fixed gates or gates which are delayed or scanned relative to and external trigger The rising e
182. res the front panel reset key is pressed or ANY command is received Because of the last restriction the BDMP command should always be the last command on a command line The binary data taken in this mode is NOT buffered The SR620 will take a data point wait until the controller has read the entire point take another point etc Thus the maximum throughput may be limited by the controller It is recommended that some form of direct memory access transfer be used to maximize the transfer rate The binary data is return as a 8 byte 2 s complement binary integer The least significant byte is always sent first and an EOI is sent with the most significant byte To convert this number to a number with the correct units the following must be done 1 Convert the 2 s complement number to signed integer form and 2 multiply by a mode dependent scaling factor The scaling factors are given below Examples of the binary dump mode are given in the Programming Examples section of the manual Scan Control Commands ANMD 7 j The ANMD command sets the mode of the rear panel DAC outputs The parameter j 0 sets output 0 to produce a voltage proportional to the measurement mean value and DAC output 1 to produce a voltage proportional to the jitter of the measurement The parameter j 1 sets output O to be a programmable voltage source and output 1 to be proportional to the jitter The parameter j 2 sets output O to be proportional to the
183. riggering occurs between about 1 8 and 0 8V 5 Set the B input to AC and verify that triggering occurs between about 0 5 to 0 5 V Counter Channel Tests 1 Set the SR620 to TIME mode A source TIME arming sample size to to 500 Automeasure on press the START button until the AUTO LED comes on and display the mean Tee the 10MHz rear panel output to the A and B inputs using equal length cables from the tee to the inputs Set the A and B inputs to 50 ohms and the trigger levels to 0 0V 2 Set the A and B slopes to The display should read less than 1ns 3 Set the display to jitter The reading should be less than 50ps 4 Set the mode to frequency the arming to 0 1s gate the source to A sample size to 1 The display should read 10 MHz 35mHz 9999999 965 to 10000000 035 Hz 5 Set the gate size to 1s The display should read 10MHz 3 5mHz 6 Set the A input to UHF The reading should be 10MHZ 3 5mHz 7 Set the source to B and the B input to UHF The reading should be 10MHz 3 5mHz Rear Panel Tests 1 Attach the x and y scope outputs to an oscilloscope in x y mode Set the scope input channel to 1 V div Make sure that the displayed picture is free of major distortion or anomalies Minor distortion can be caused by poorly compensated scope inputs 2 Attach the printer to the printer port Press the print button The printed graph should be the same as the displayed graph THIS COMPLETES THE
184. roperly To configure the SR620 you must set the GPIB address in line 2 of the Control CONFIG menu The default GPIB address is 16 use this address unless a conflict occurs with other instruments in your system The SR620 will be set to GPIB address 16 whenever a COLD BOOT is done if the RESET key is held down when the unit is turned ON Make sure that you follow all the instructions for installing the GPIB card The National Instruments card cannot be simply unpacked and put into your computer To configure the card you must set jumpers and switches on the card to set the I O address and interupt levels You must run the program IBCONF to configure the resident GPIB driver for your GPIB card Please refer to the National Instruments manual for additional information Once all the hardware and GPIB drivers are configured use IBIC This terminal emulation program allows you to send commands to the SR620 directly from your computer s keyboard If you cannot talk to the SR620 via IBIC then your programs will not run Use the simple commands provided by National instruments Use IBWRT and IBRD to write and read from the SR620 After you are familiar with these simple command you can explore other more complex programming commands SR620 Universal Time Interval Counter Programming Examples __ 45 Program Example 2 IBM PC Microsoft FORTRAN V4 0 National Instruments GPIB Card This example demonstartes using the SR620 via the GPIB Mi
185. se shape at the end of the line A 4 V step at the source will launch a 2 V wave The line which has a characteristic impedance of about 100 Ohms will provide a SR620 Universal Time Interval Counter 82 Circuit Description 100 positive reflection at the high impedance termination into the TTL or HC device which receives the signal The reflection is then reverse terminated into the 82 Ohm resistor and the low impedance output of the sending device The result is a logic signal with very little distortion at the far end of the line FAST TIME INTERVAL LOGIC Sheet 10 of 16 To measure a time interval the 90 MHz clock is counted for the interval between a start pulse and a stop pulse Each tick of the clock represents 11 111 ns of time interval To attain a resolution of 4 ps the times from the start pulse and stop pulse to subsequent edges of clock are measured with 4 ps resolution The time interval is then 11 111 ns x clocks Time from Start to clock Time from Stop to clock ECL flip flops have the unfortunate problem that the propagation delay from clock to output will be affected if either the reset or data inputs arechanged simultaneously with the clock In order to meet the stringent accuracy and jitter specifications for the instrument it is necessary to use two stage resynchronization A rising edge on the ECL bit Start_Mpx sets the start latch U604A asserting Start To avoid the possibility that the
186. sistor Carbon Film 1 4W 5 Parts List 99 REF SRS PART VALUE DESCRIPTION R 330 4 00021 401 1 0K Resistor Carbon Film 1 4W 5 R 331 4 00081 401 470 Resistor Carbon Film 1 4W 5 R 332 4 00031 401 100 Resistor Carbon Film 1 4W 5 R 333 4 00048 401 2 2K Resistor Carbon Film 1 4W 5 R 334 4 00057 401 220 Resistor Carbon Film 1 4W 5 R 335 4 00031 401 100 Resistor Carbon Film 1 4W 5 R 336 4 00021 401 1 0K Resistor Carbon Film 1 4W 5 R 337 4 00031 401 100 Resistor Carbon Film 1 4W 5 R 338 4 00031 401 100 Resistor Carbon Film 1 4W 5 R 339 4 00083 401 47K Resistor Carbon Film 1 4W 5 R 340 4 00083 401 47K Resistor Carbon Film 1 4W 5 R 341 4 00034 401 10K Resistor Carbon Film 1 4W 5 R 342 4 00034 401 10K Resistor Carbon Film 1 4W 5 R 343 4 00034 401 10K Resistor Carbon Film 1 4W 5 R 345 4 00176 407 3 01K Resistor Metal Film 1 8W 1 50PPM R 346 4 00130 407 1 00K Resistor Metal Film 1 8W 1 50PPM R 347 4 00188 407 4 99K Resistor Metal Film 1 8W 1 50PPM R 348 4 00464 407 6 98K Resistor Metal Film 1 8W 1 50PPM R 349 4 00032 401 100K Resistor Carbon Film 1 4W 5 R 350 4 00080 401 47 Resistor Carbon Film 1 4W 5 R 351 4 00086 401 51 Resistor Carbon Film 1 4W 5 R 360 4 00031 401 100 Resistor Carbon Film 1 4W 5 R 361 4 00031 401 100 Resistor Carbon Film 1 4W 5 R 362 4 00027 401 1 5K Resistor Carbon Film 1 4W 5 R 363 4 00027 401 1 5K Resistor Ca
187. stable delay is inserted between the EXT input trigger and the arming circuitry This delay may be used in any of the externally triggered arming modes This allows one to arm a measurement at a time other than when the external trigger arrives This would be useful for example if one wanted to measure the frequency of an oscillator as a function of time from a sudden change in frequency The signal that causes the change would be the external trigger and by adjusting the delay one could measure the frequency as a function of time DELAYED GATES AND TRIGGERS EXT TRIGGE DELAYED GATE Edge arms time interval measurements gate may be used for STOP HOLD OFF Gate used for treq per count measurements 1s n s 50 000 W tus 10ms in 1 2 5 sequence PHASE 360 x At PHASE At N SR620 Universal Time Interval Counter 16 Sample Arming The delay may be adjusted in step sizes ranging from ims to 10ms and the total delay may be set between 1 and 50000 steps In modes such as frequency period and TIME EXTERNAL STOP HOLDOFF that require an external input of some width the delay will be followed by a gate one step size wide not the width of the external trigger pulse The SR620 has the ability to automatically scan the trigger delay after each measurement This is discussed in the SCANNING section of the CONFIGURATION MENU chapter of this manual If the delay feature is enabled the EXT led in the
188. start pulse comes just as the reset to the start latch is released the start pulse to the start latch is delayed the undelayed start pulse clocks U604B high synchronously releasing the reset to the start latch In this way the reset to the start latch always precedes the clock to the start latch by about 3 ns Once the start latch is set the next rising edge of the 90 MHz clock will set U605A and the second edge of the clock will set U605B The signal Start Ck is on from the start edge until the second edge of the 90 MHz after the start signal This 12 23 ns wide pulse will be integrated to measure the time by which the start pulse preceded the 90 MHz clock edge The same scheme is used to generate a Stop bit and Stop Ck pulse A Time Gate is also generated this bit is on for the interval between the start and the stop resynchronized to the 90 MHz clock Time_Gate is used to gate the 90 MHz clock to a counter to measure the number of 90 MHz clock ticks in the time interval SR620 Universal Time Interval Counter The flip flop U311B saves the state of the synchronized stop bit prior to the last rising edge of the 90 MHz clock This will set the bit Neg_Time high when the stop pulse proceeds the start pulse TIME INTERVAL ARMING Sheets 9 and 10 of 16 There are several different ways that the start and stop circuits may be armed In each case the circuits are armed by removing the reset and by providing a high ECL level
189. t C version 5 1 The header file for the GPIB interface is ms c488 h and is supplied by CEC To compile this program use the command CL AL FPi c bindump c The resulting object file is then linked with GPIB L OBJ from CEC and the emulation math library which doesn t assume a math coprocessor include lt stdio h gt include lt string h gt include lt stdlib h gt include lt math h gt include lt ms c488 h gt include lt dos h gt define sr620 16 TIC address void main void void InitGpib void void TxGpib int char function prototypes void GetGpib int void StatCheck int void TalkGpib int void Convert int int int int status length mode count char recv 80 the data from each point is stored in 4 consecutive array locations int data 20000 up to 5000 points double fdata 5000 data storage for converted data void main char cmd 40 input 40 int i samples seg tmode texpd static char units s s s Hz s deg ct InitGpib initialize controller while 1 read number of samples printf Enter number of samples lt cr gt to quit gt gets input SR620 Universal Time Interval Counter Programming Examples _53 if strlen input break quit if no number sscanf input d amp samples if samples gt 5000 continue try again if too large set up parameters for dma input mod
190. t binary dump mode allows up to 1500 measurements per second to be taken and transfered to a computer Front Panel Operation 3 FRONT PANEL OPERATION The SR620 Universal Time Interval Counter can perform an extremely wide variety of time interval and frequency measurements The SR620 is designed so that the values of virtually all of the important measurement parameters are visible at a glance on the front panel Setting the SR620 to perform a particular measurement can be separated into three steps choosing the measurement choosing the output display and setting the inputs The SR620 is different than most counters in that a measurement consists of from 1 to 1 000 000 samples and the SR620 reports statistical information on these samples The SR620 can report the mean jitter maximum and minimum values found in a measurement CHOOSING THE MEASUREMENT MODE SOURCE GATE ARM START a Lat a ETH gao ma wu p Ne A SETTING THE MODE Pressing the MODE up and down arrow keys sets the measurement type The SR620 can measure time intervals pulse widths pulse rise and fall times frequency period phase and can count events The ARMING section has detailed explanations of the modes SETTING THE SOURCE The source key selects the signal source for a particular measurement In time interval mode the source specifies which input will start the time interval Normally the start source is channel A b
191. tain combinations of histogram horizontal scales and bin sizes PDEV j The PDEV command sets the hardcopy output device The parameter j O set the device to printer while j 1 sets it to plotter PLAD j The PLAD command sets the address of the GPIB plotter if a plotter is being used Any address from O to 30 except the current address of the SR620 may be used PLPT 7 j The PLPT command sets the plotter output port to either RS232 or GPIB The parameter j O set the port to RS232 while j 1 sets the port to GPIB PLOT The PLOT command starts a plot or print PCLR The PCLR command clears any plots or prints in progress SR620 Universal Time Interval Counter Front Panel Control KEYS j The KEYS command simulates the pressing of a front panel key The KEYS query returns the keycode of the most recently pressed key Keycodes are assigned as follows Key keycode mode up 16 mode down 17 source 18 size up 25 size down 27 measurement start 32 measurement reset 34 display up 33 display down 35 set rel 40 clear rel 42 set graph 43 autoscale 41 display scales 22 scale up 20 scale down 23 print 21 clear print 29 config select 28 config set 30 Ext slope 36 Manual Trigger 31 Ext termination 39 A slope 37 A ac dc 38 A termination 47 B slope 44 B ac dc 46 B termination 45 ref level 19 set auto measure 50 set autoprint 51 clear automeasure 52 clear autoprint 53 Programming Comma
192. tatus enable registers or maintain them in the state they were in on power down The action taken is set by the PSC command and allows things such as SRQ on power up Serial Poll Status Byte bit name usage 0 ready No measurements are in progress 1 print ready No prints are in progress 2 Error An unmasked bit in the error status register has been set 3 TIC An unmasked bit in the TIC status register has been set 4 MAV The gpib output queue is non empty 5 ESB An unmasked bit in the standard status byte has been set 6 RQS MSS SRQ Service Request bit 7 scan ready no scans are in progress The Error TIC ESB bit are set whenever any unmasked bit bit with the corresponding bit in the Programming Commands 41 byte enable register set in their respective status registers is set They are not cleared until the condition which set the bit is cleared Thus these bits give a constant summary of the enabled status bits A service request will be generated whenever an unmasked bit in the serial poll register is set Note that service requests are only produced when the bit is first set and thus any condition will only produce one service request Accordingly if a service request is desired every time an event occurs the status bit must be cleared between events Standard Event Status Byte bit name usage 0 OPC Set by OPC command when all operations are complete 1 unused 2 Query Error Set on output queue
193. ter j O selects normal mode while j 1 selects autolevel mode Once autolevel is selected it will remain in effect until the level is set by the LEVL command it is turned off by the TMOD command or the front panel knob is rotated TSLP if j The TSLP command selects the trigger slopes of the EXT A and B inputs The parameter j O selects positive slope while j 1 selects negative slope Measurement Control Commands TRG The TRG command is the device trigger common command It functions identically to the STRT command and to pushing the front panel START button ARMM j The ARMM command selects the SR620 s arming mode The parameter j sets the mode according to the following table The measurement modes in which a particular type of arming is allowed is also shown j arming mode measurement modes O time time 1 time time width rise fall time phase 2 1 period frequency period 3 0 01s gate frequency period count 4 0 1s gate frequency period count 5 1 0s gate frequency period count 6 ext trig time time 7 ext trig time time width rise fall time phase 8 extgate time hldf time width frequency period count 9 exttriggered 1 period frequency period 10 ext triggered 01s gate frequency period count 11 ext triggered 0 1s gate frequency period count 12 ext triggered 1 0s gate frequency period count Use of the scanning internal gate requires that the unit
194. ter representation and sets gate and trigger scales SR620 Universal Time Interval Counter Output Configuration Menus Line Default Display Comments grAPh on 2 outPut PrintEr Enable scope displays Select Printer or Plotter for hardcopy Specify RS 232 or GPIB for plotter port Specify plotters GPIB address Set printer port mode DVM 1 and DVM 2 full scale range Specify Standard deviation or Allan Variance sets the gate scale factor sets trigger knobs full scale range 3 Plot Port rS232 4 PlottEr Addr 5 5 Pm Port Print 6 ScALE Auto Auto 7 JitEr Std dEv 8 GatE ScAIE 1 9 trig ScAIE 5 00 The scope displays may be disabled by turning graphs off in the first line of the output menu Turning the graphs off will reduce the dead time at the end of a measurement from 60 ms to about 3 ms The next line is used to select the hardcopy device If a printer is specified as the hardcopy device then it must be connected to the Centronics compatible printer port The printer must be an Epson compatible printer with graphics capabilities Virtually all printers used with PC s will suffice The printer may be connected to the SR620 with the same printer cable which is used with a PC If a plotter is specified the plotter may be connected to either the RS 232 port or the GPIB port The port which is used for the plotter must be specified in the next line of the output menu The plotter should be s
195. the status bit or using a GPIB service request the host computer would know when the measurement was done SR620 Universal Time Interval Counter 38 Programming Commands WAI The WAI wait common command is a synchronization command that holds off all further command execution until all in progress measurements scans prints are complete This command ensures that a particular operation is finished before continuing An example of the usefulness of this command is ensuring that a measurement is complete before reading the answer The command line STRT WAI XAVG will start a measurement wait until it is done and send back the mean value ENDT j k I m The ENDT command sets the RS232 end of transmission terminator This terminator is appended the the end of each answer and may consist of up to 4 ASCII decimal characters The default terminator is lt cr gt lt If gt and is obtained by omitting the parameters The parameters j k m are the decimal representations of between 1 and 4 termination characters For example if it desired that the termination be the characters carriage return and E the command would be ENDT 13 69 STUP The STUP query returns the complete setup of the SR620 as a long string of numbers separated by commas All setup information except for trigger levels and d a starting and step voltages is returned The meanings of the returned numbers are as follows when bits are packed into a status byte t
196. the status enable registers ESE 2 j The ESE command sets the standard event status byte enable register to the decimal value j ESR j The ESR common command reads the value of the standard event status register If the parameter j is present the value of bit j is returned Reading this register will clear it while reading bit j will clear just bit j PSC j The PSC common command sets the value of the power on status clear bit If j 1 the power on status clear bit is set and all status registers and enable registers are cleared on power up If j 0 the bit is cleared and the status enable registers maintain their values at power down This allows the production of a service request at power up SRE 2 j The SRE common command sets the serial poll enable register to the decimal value of the parmeter j STB j The STB common query reads the value of the serial poll byte If the parameter j is present the value of bit j is returned Reading this register has no effect on its value as it is a summary of the other status registers EREN j The EREN command sets the error status enable register to the decimal value j ERRS j The ERRS query reads the value of the error status byte If the parameter j is present the value of bit j is returned Reading this register will clear it while reading bit j will clear just bit j STAT j The STAT query reads the value of the time interval
197. the beam in the middle of the screen and attach the inputs to the X Y display outputs on the rear panel of the SR620 Press the AUTO key in the SCOPE AND CHART section to scale the display If the DISPLAY REL is set the HISTOgram of the pulse widths will be displayed with about 20 ps div horizontal resolution In the SCOPE AND CHART section press the display button to change from HIST to MEAN Press the AUTO button to scale the display The scope will now show a strip chart of the mean values for each set of measurements Now select JITTER and press AUTO to display a strip chart of standard deviations for the scope display SR620 Universal Time Interval Counter 2 Instrument Overview Introduction The SR620 Time Interval Counter can do a variety of time interval and frequency measurements The instrument s high single shot timing resolution low jitter and reciprocal counting architecture allow rapid high resolution measurements Modes of Operation Time Intervals between the A and B inputs may be measured with 4 ps LSD 25 ps rms resolution 100 ps relative accuracy and ns absolute accuracy Time intervals from 1ns to 1000 s or 1000 s may be measured Pulse Widths of either input may be measured The start and stop thresholds are set separately The resolution jitter and accuracy are the same as for Time interval measurements Rise and Fall Times of either input may be measured The start and stop thresh
198. the duration of the Start_Ck and Stop_Ck pulses The descriptions of the two integrators are identical circuit references will be made to the Start_Ck integrator The integrating capacitor C701 integrates a constant current source for the duration of the Start_Ck pulse The change of voltage change on this capacitor is proportional to the width of the START_TO_CK pulse Before the unit is triggered U701A an operational transconductance amplifier OTA precharges the integrating capacitor to about 7 vdc When the Start is asserted Q702 is turned off and Q701 is turned on turning off the OTA At the same time the constant current source at the common emitters of U702A is switched from N701A to N701B to discharge the integrating capacitor at a constant rate The discharge is stopped when the Start_Ck pulse terminates The constant current source is maintained by U703A amp B which holds the voltage across R714 constant The time to voltage gain coefficient is calibrated by the dc voltage Start_Gain The integrating capacitor s voltage is buffered and amplified by U703C The amplified output will range from 3 33 Vdc with some offset This voltage is sampled and held by the analog switch U705A on the polypropylene capacitor C706 The analog switch is turned on for about 7 us by the one shot U704A Another analog switch U705D is released just before the signal is sampled this switch is used to discharge the capacito
199. the range of 10 VDC with 5 mV resolution Delay scans allow measurements of timing frequency phase etc versus delay from an external trigger Example the frequency of a VCO as a function of time after a voltage step is applied Scan Configuration Menu Line Default Display Comments 1 ScAnEnA oFF_ Enable disable delay and voltage scans 2 ScAnPtS 250 Set the number of point in a scan 3 hold 01 Sec Set dwell time between points 4 dASre chrtchrt Set D A function strip chart or D A 5 dA Set D A voltage when configured as D A 6 Step Set D A step size for voltage scans 7 GELAy Scan oFF Enable disable delay scans 8 gAtE StEP 1E 6 Set gate width and step size 9 StArt 0 000001 Set delayed gate start position The scan menu is used to set and scan D A values gate widths and gate delays from an EXT input The scan menu allows one to compose a graph on an XY scope of a particular measurement frequency for example vs time or voltage The first line of the scan menu is used to enable scans Scans may be turned oFF or set to SingLE or rEPEAt In the single setting the the SR620 will take one scan and stop In the repeat mode the SR620 will automatically reset the scan parameters at the end of a scan and start another scan In either mode pressing the START button will take a single scan point while SR620 Universal Time Interval Counter 20 Configurati
200. trol 18 Input Termination 9 Jitter Type Selection 19 UHF Prescalers 9 Gate Scale Multiplier 19 Input Coupling 10 Trigger Knob Range 19 Reference Output 10 Timebase Input and Output 10 SCAN Menu 19 DVM Inputs 10 Enabling Scans 19 Setting D A outputs 20 Sample Arming 11 Scanning the D A s 20 External Trigger Delays 20 TIME Mode 11 Scan Examples 20 Time Interval Arming 11 Specification Guide 23 TIME 11 TIME EXT 12 Definition of Terms 23 TIME EXT with HOLDOFF 12 Least Significant Digit 23 TIME 12 Resolution 23 TIME EXT 12 Error 23 Differential Non linearity 23 SR620 Universal Time Interval Counter Table of Contents Timebase Specifications Short Term Stability Long Term Stability External Timebases Trigger Input Specifications Measurement Accuracy Programming SR620 Universal Time Interval Counter Programming the SR620 Communications GPIB Communication RS 232 Communication Data Window Command Syntax Detailed Command List Trigger Commands Measurement Control Data Transmission Binary Dump Scan Control Graphics Control Front Panel Control Interface Control Status Reporting Calibration Commands Serial Poll Status Byte Event Status Byte TIC Status Byte Error Status Byte Programming Examples BASIC and RS 232 FORTRAN National Instruments BASIC GPIB Binary Dump FORTRAN GPIB Binary Dump C GPIB Binary Dump Test and Calibration Troubleshooting Tips Troubleshooting Power up Error Messages CAL
201. uired to maintain very low jitter on the calibration signal The driver for the reference output may be programmed for either ECL or TTL output levels by the bit TTL ECL The driver has a 50 Ohm output impedance which supplies 4V to high impedance loads 2V to 50 Ohm loads and ECL SR620 Universal Time Interval Counter levels 0 8 to 1 8V to 50 Ohm loads to ground The rise and fall times for this output are about 2 ns An internal calibration signal Int_Cal is also driven by the resynchronized 1 kHz ECL signal This calibration signal is used to linearize and set the gain of the time to amplitude converters The calibration signal provides a linear ramp of about 30 ns duration which is accurately phased to the internal 10 MHz timebase The linear ramp is generated by discharging C222 with a constant current source The constant current source is turned on by the 1 kHz reference signal C222 is passively recharged to 10 vdc by R226 and R239 The FET source follower Q228 provides a low impedance output DELAY AND GATE GENERATOR Sheet 6 of 16 An internal gate generator is used to provide 01 1 and 1 second gates for FREQuency PERIOD PHASE and COUNT mode measurements The gate generator may also be set for gates from 1 us to 1 s via the front panel configuration menu or computer interfaces For non delayed gates including the front panel selectable gates of 01 1 and 1 s the control line Clk_On is set low wh
202. uit Diagrams Sheet No Front Rear Panel Summary Counter Visual Index Microprocessor System 1 16 GPIB RS232 Printer Interfaces 2 16 Scope Graphics Controller 3 16 I O Ports and LED Drivers 4 16 Analog and ECL I O 5 16 Slow Counters and REF OUT 6 16 Fast Clocks and Timebase 7 16 Front End Input Comparators 8 16 ECL Mpx Freq Gating Counters 9 16 Fast Time Interval Logic 10 16 Time Interpolators 11 16 A D D A and Threshold pots 12 16 Unregulated Power Supplies 13 16 Power Supply Regulators 14 16 Spares and Decoupling 15 16 Front Panel Display PCB 16 16 Component Placement on PCB SR620 Universal Time Interval Counter iv Table of Contents SR620 Universal Time Interval Counter Safety and Preparation for Use _v Safety and Preparation for Use WARNING Dangerous voltages capable of causing death are present in this instrument Use extreme caution whenever the instrument covers are removed This instrument may be damaged if operated with the LINE VOLTAGE SELECTOR set for the wrong ac line voltage or if the wrong fuse is installed LINE VOLTAGE SELECTION The SR620 operates from a 100V 120V 220V or 240V nominal ac power source having a line frequency of 50 or 60 Hz Before connecting the power cord to a power source verify that the LINE VOLTAGE SELECTOR card located in the rear panel fuse holder is set so that the correct ac input voltage value is visible Conversion to other ac input voltages requires a chang
203. unit warms up The red LED labeled CLOCK in the CONFIG section may stay on for a few minutes The red LED s labeled START and STOP may blink if no inputs are applied Press the MODE down key once to select the WIDTH mode Press the source key twice to select REF the 1 kHz REFerence as the signal source After 1 2 hour warmup the display should read 500 us 1 ns If the displayed value is outside this range see instructions for running the AUTOCAL procedure Press the SAMPLE SIZE up key five times to select a sample size of 500 This will slow the display update rate to 2 Hz and provide a more consistent MEAN value Press the SET key in the DISPLAY section to set the REL offset to the current value of the 6 7 8 9 Quick Start Instructions 1 MEAN The REL LED will turn on and the display will show a mean value within a few ps of zero An r appears on the display to indicate a relative value Press the DISPLAY down key to show each of the following MEAN 0 100 ps The REL is set REL 500 us 100 ps JITTER 5 20 ps MAX Erratic but usually lt 100 ps MIN Erratic but usually lt 100 ps TRIG 5 V per the three level knobs DVM Within 5 mV of zero Configure an oscilloscope for the X Y display mode with the horizontal and vertical inputs set for dc coupling not 50 Ohms and 1 V div sensitivity If the scope has scale factor displays turn them off and set the 20 MHz bandwidth limit Center
204. ut channel B and the 1kHz REF output may also be selected The other input then stops the time interval In pulse width frequency period and counts the source may be A B or the 1kHz REF Additionally in frequency period and count modes if both the A and B LEDs are on the RATIO A B is measured In rise fall time mode only A and B may be the source while in phase mode the phase of B relative to A is always measured SETTING THE ARMING MODE Arming controls the conditions under which a sample is started and stopped The arming mode is chosen using the ARMING up and down arrow keys The SR620 has a large selection of arming modes The various modes relevant to each particular type of measurement are treated in detail in the ARMING section of this manual A summary of the arming modes is given on the next page SELECTING THE NUMBER OF SAMPLES The sample size up and down arrow keys select between 1 and 1 000 000 samples for the measurement STARTING AND STOPPING MEASUREMENTS The START and RESET keys start and stop measurements Press the START key to start a single measurement The BUSY LED will remain on while the measurement is in progress When the measurement is finished the SR620 will display the results and stop Press and hold the START key to turn on the AUTO LED and automeasure When automeasure is on the SR620 will automatically start a new measurement when the present one is complete Press the RES
205. utolevel 4 test error 5 cal error Set when the auto cal routine detects an error 6 warmup Set when unit is warmed up after power on 7 ovfl divO Set when internal counters overflow or on ratio mode divide by 0 These bits stay set until cleared by reading or by the CLS command SR620 Universal Time Interval Counter 42 Programming Commands SR620 Universal Time Interval Counter Programming Examples __ 43 PROGRAMMING EXAMPLES THROUGHPUT The actual time required to make a measurement of N samples is given by the equation T Nx Tsample measured time interval calculation time The sample time Tsample is given in the table below TIME WIDTH Tr Tf 750us FREQ PERIOD 2600us GRAPHS ON 200us ASCII RESPONSES 250us So when measuring short time intervals with graphs on and not in the binary dump mode the SR620 has a throughput of about 1000 samples per second There is some additional time required at the end of each group of measurements This calculation time is zero no graphic displays binary responses or 5 ms no graphic displays ASCII responses or 8 ms active chart outputs or scope display of mean or jitter to 50 ms scope display of histogram If the SAMPLE SIZE is greater than one then statistics will be calculated which will add 10 100 ms to the calculation time depending on the number of digits in the MEAN value The data acquisition rate to a computer will depend on the interface which is used
206. y by conversion factor fdata i factors tmode fdata i C change scale if expand is on if texpd eq 1 fdata i fdata i 1 0D 3 10 continue return end C kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk C initialize the CEC GPIB card as a controller Subroutine InitGpib integer 2 status data str IFC UNT UNL DCL REN call INITIALIZE 21 0 call TRANSMIT IFC UNT UNL DCL REN status return end C kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk C makes device at address a talker subroutine TalkGpib address character 25 cmd integer 2 status address write cmd 100 address 100 format UNT UNL MLA TALK 12 call TRANSMIT cmd status call StatCheck address status return end C kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk C transmit command to address subroutine TxGpib address command character 30 command character 70 tstring character 2 temp integer 2 status address tstring 1 19 UNT UNL MTA LISTEN write temp 100 address 100 format 12 C set up CEC command string tstring 20 21 temp SR620 Universal Time Interval Counter Programming Examples 51 tstring 22 27 DATA tstring 28 58 command tstring 59 64 END call TRANSMIT tstring status call StatCheck address status return end C kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk C get an answer from a device subroutine
207. y pressing the button or a programming command before the current copy is finished the SR620 will stop taking data until the current copy is done This is to avoid corrupting the second copy as the SR620 only has a 1 deep graphics output queue The output device printer or plotter is chosen in the CONFIGURATION menu see that section for detail When using a printer the SR620 may be put into autoprint mode by pressing and holding the PRINT key until the AUTO LED turns on In autoprint mode the SR620 will automatically print every histogram or a new stripchart each time the stripchart fills up There is no autoprint when using a plotter because the paper needs to be changed In autoprint mode the speed of the printer may determine the measurement rate if new graphs are generated faster than the printer can print them A print or plot may be aborted by pressing the CLR button under the PRINT button Pressing and holding the CLR button will turn off autoprint If the message print error or plot error appears while printing or plotting please refer to the TROUBLESHOOTING section CHART OUTPUTS In addition to the scope outputs the SR620 also has two rear panel analog outputs designed to go to analog chart recorders One output puts out a voltage proportional to the mean of the measurement while the other output puts out a voltage proportional the jitter of the measurement The output range is 0 8V corresponding to the 8 vertical sco

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