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SR510 Lock-In Amplifier - Stanford Research Systems

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1. OPEN COM1 9600 N 8 2 CS DS CD AS 1 SET UP COM1 PORT TO 9600 BAUD NO PARITY 8 DATA BITS i IGNORE CTS CLEAR TO SEND DSR DATA SET R AND CD CARRIER DETECT r PRINT 1 CLEAR UART BY SENDING SPACES PRINT 1 Z RESET SR510 FOR I 1 TO 200 NEXT I FOR RESET TO FINISH r X INIT X6 OUTPUT TO ZERO r PRINT 1 READ OUTPUT INPUT 1 V1 INTO V1 r PRINT OUTPUT V1 r X X 0025 OUTPUT BY 2 5 MV IF X gt 10 THEN X 0 RESET X6 RAMP PRINT 1 USING X SET OUTPUT VOLTAGE r GOTO 190 LOOP FOREVER 42 EADY Program Example 2 IBM PC Microsoft Fortran v3 3 via RS232 Machine language routines to interface to the To use these routines the file for232 inc also on 1 RS232 port are provided in the file the SR575 disk must be included in the RS232 OBJ found on the SR575 disk These FORTRAN source routines allow for simple interfacing to the SR510 at 19 2 kbaud from FORTRAN programs Only two wires between the IBM PC s ASYNC port and the SR530 are needed pins 2 amp 3 of the RS232 but pins 5 6 8 and 20 should be connected together on the connector at the IBM end storage 2 Sinclude for232 inc 20 1000 for 232 inc must be included to call subroutines in RS232 0BJ link with RS232 0BJ on SR565 disk RS232 0BJ defines init initializes 1 to 19 2 kbaud txstr str str is a string t
2. Appendix C GPIB Introduction to the GPIB Bus Description Appendix D Program Examples IBM PC Microsoft Basic via RS232 IBM PC Microsoft Fortran via RS232 IBM PC Microsoft C via RS232 IBM PC Microsoft Basic via GPIB HP 85 HP Basic via HPIB Documentation Part Numbering and Locations Parts List Main Assembly Parts List Internal Oscillator Parts List Miscellaneous Parts List Front Panel Schematic Diagrams 41 42 43 47 49 Safety and Preparation for Use CAUTION This instrument be damaged if operated with the LINE VOLTAGE SELECTOR set for the wrong applied ac input source voltage or if the wrong fuse is installed LINE VOLTAGE SELECTION The SR510 operates from a 100V 120V 220V or 240V nominal ac power source having a line frequency of 50 or 60 Hz Before connecting the power cord to a power source verify that the LINE VOLTAGE SELECTOR card located in the rear panel fuse holder is set so that the correct ac input voltage value is visible Conversion to other ac input voltages requires a change in the fuse holder voltage card position and fuse value Disconnect the power cord open the fuse holder cover door and rotate the fuse pull lever to remove the fuse Remove the small printed circuit board and select the operating voltage by orienting the printed circuit board to position the desired voltage to be visible when pushed firmly into its slot Rotate the fuse pull lever back into its n
3. Resistor Carbon Film 1 4W 596 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Switch Toggle Right Angle PCB Mount Switch Toggle Right Angle PCB Mount Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Transistor TO 92 Package Transistor TO 92 Package Washer Flat Wire 424 UL1007 Strip 1 4x1 4 Tin Wire 424 UL1007 Strip 1 4x1 4 Tin DESCRIPTION Fabricated Part EPROM PROM I C Nut Mini Standoff Screw Roundhead Phillips Hardware Misc Hardware Misc Screw Panhead Phillips Screw Panhead Phillips Hardware Misc Screw Panhead Phillips Screw Black All Types Screw Black All Types Screw Black All Types Fuse Fabricated Part Fabricated Part Fabricated Part Fabricated Part Fabricated Part Front Panel Parts List SR510 PARTS LIST REF SRS parti VALUE 1 C601 5 00019 501 68P 2 C602 5 00019 501 68P 3 C608 5 00052 512 010 4 C604 5 00052 512 01U 5 C605 5 00056 512 1U 6 C606 5 00056 512 1U 7 C607 5 00023 529 1U 8 D601 3 00004 301 1 4148 9 D602 3 00004 301 1 4148 10 D 603 3 00004 301 1 4148 11 D604 3 00004 301 1 4148 12 DS601 3 00012 306 GREEN 13 05602 3 00012 306 GREEN 14 DS603 3 00012 306 GREEN 15 05604 3 00012 306 GREEN 16 05605 3 00012 306 GREEN 17 DS606 3 00012 306 GREEN 18 05607 3 00012 306 GREEN 19 05608 3 00012 306 GREEN 20 DS609 3 00012 306 GREEN 21 DS610 3 00012 306 GREEN 22 05
4. 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 SR510 PARTS LIST REF SRS parti VALUE 458 R433 4 00021 401 1 0K 459 R501 4 00022 401 1 0 460 R502 4 00022 401 1 0M 461 R503 4 00022 401 1 0 462 R504 4 00022 401 1 0 463 R505 4 00034 401 10K 464 R506 4 00034 401 10K 465 R507 4 00034 401 10K 466 R508 4 00034 401 10K 467 R509 4 00218 408 10 00 468 R510 4 00219 408 20 00 469 R511 4 00218 408 10 00 470 R512 4 00219 408 20 00 471 R513 4 00166 407 200K 472 R514 4 00207 407 806K 473 R515 4 00021 401 1 0K 474 R516 4 00021 401 1 0K 475 R518 4 00034 401 10K 476 R519 4 00021 401 1 0K 477 R520 4 00086 401 51 478 R521 4 00086 401 51 479 R 522 4 00218 408 10 00 480 R523 4 00218 408 10 00 481 R524 4 00078 401 39K 482 R525 4 00059 401 22K 483 R526 4 00032 401 100K 484 R527 4 00021 401 1 0K 485 R528 4 00034 401 10K 486 R529 4 00057 401 220 487 R530 4 00210 407 9 09 488 R531 4 00130 407 1 00 489 R532 4 00032 401 100 490 R533 4 00032 401 100K 491 R534 4 00034 401 10K 492 R535 4 00057 401 220 493 R536 4 00034 401 10K 494 R537 4 00057 401 220 495 R538 4 00034 401 10K 496 R539 4 00057 401 220 497 R540 4 00034 401 10K 498 R541 4 00057 401 220 499 R542 4 00034 401 10K 500 R543 4 00034 401 10K 501 R544 4 00042 401 15K 502 R545 4 000
5. 510 5 00054 512 0470 124 C511 5 00054 512 0470 125 C512 5 00054 512 0470 126 C513 5 00054 512 0470 127 C 514 5 00049 566 0010 128 C515 5 00049 566 001U 129 C516 5 00049 566 001U 130 C517 5 00002 501 100P 131 C518 5 00056 512 1U 132 C519 5 00049 566 001U 133 520 5 00052 512 010 134 521 5 00052 512 010 135 523 5 00052 512 010 136 525 5 00052 512 010 137 526 5 00023 529 10 138 527 5 00023 529 10 139 701 5 00007 501 220P 140 702 5 00007 501 220 141 703 5 00040 509 1 00 142 704 5 00040 509 1 00 143 705 5 00052 512 010 144 706 5 00052 512 010 145 707 5 00052 512 01U 146 708 5 00052 512 010 147 709 5 00052 512 01U 148 C710 5 00052 512 010 149 C711 5 00052 512 01U 150 C712 5 00052 512 01U 151 C713 5 00014 501 390 53 DESCRIPTION Stacked Metal Film 50V 5 40 85c Stacked Metal Film 50V 5 40 85c Stacked Metal Film 50V 5 40 85c Cap Polyester Film 50V 5 40 85c Rad Stacked Metal Film 50V 5 40 85c Capacitor Mylar Poly 50V 5 Rad Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Polyester Film 50V 5 40 85c Rad Capacitor Ceramic Disc 50V 1096 SL Capacitor Ceramic Disc 50V 1096 SL Capacitor Ceramic Disc 50V 1096 SL Capacitor Polystyrene 50V 596 Rad
6. Introduction to the GPIB Capabilities Response to Special GPIB commands Serial Polls and SRQ s Echo Mode using the RS232 Using Both the RS232 amp GPIB Lock in Technique Introduction to Lock in Amplifiers Measurement Example Understanding the Specifications Shielding and Ground Loops Dynamic Reserve Current Input Auto Tracking Bandpass Filter Notch Filters Frequency Range Noise Measurements Output Filters Ratio Capability Computer Interface Internal Oscillator SR510 Block Diagram Block Diagram Signal Channel Reference Channel Phase Sensitive Detector DC Amplifier and System Gain Microprocessor System Circuit Description Introduction Signal Amplifier Current Amplifier Notch Filters Bandpass Filter Reference Oscillator PSD LP Filters and DC Amplifier Analog Output A D s D A s Expand Front Panel Microprocessor Control RS232 Interface GPIB Interface Power Supplies Internal Oscillator Calibration and Repair Introduction Multiplier Adjustments Amplifier and Filter Adjustments CMRR Adjustment Line Notch Filter Adjustment 2xLine Notch Filter Adjustment Repairing Damaged Front End Appendix A Noise Sources and Cures Johnson Noise 1 f Noise Noise Spectrum Capacitive Coupling Inductive Coupling Ground Loops Microphonics Thermocouple Effect Appendix B RS232 Simplest Case Using the RS232 Using Control Lines Baud Rates Stop Bits Parity Voltage Levels Eavesdropping
7. LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular SR510 PARTS LIST REF SRS part VALUE 50 DS639 3 00013 306 RED 51 DS640 3 00013 306 RED 52 DS641 3 00012 306 GREEN 53 05642 3 00012 306 GREEN 54 05643 3 00012 306 GREEN 55 05644 3 00012 306 GREEN 56 05645 3 00012 306 GREEN 57 05646 3 00012 306 GREEN 58 05647 3 00012 306 GREEN 59 05648 3 00012 306 GREEN 60 05649 3 00012 306 GREEN 61 05650 3 00012 306 GREEN 62 05651 3 00012 306 GREEN 63 05652 3 00012 306 GREEN 64 05653 3 00012 306 GREEN 65 05654 3 00012 306 GREEN 66 05655 3 00012 306 GREEN 67 05656 3 00012 306 GREEN 68 05657 3 00012 306 GREEN 69 05658 3 00012 306 GREEN 70 05659 3 00012 306 GREEN 71 05660 3 00012 306 GREEN 72 05661 3 00012 306 GREEN 73 05662 3 00012 306 GREEN 74 LD1 8 00001 820 FE0206 75 LD2 8 00001 820 0206 76 1 8 00002 801 DIV 0 77 PB601 2 00001 201 06 01 01 78 602 2 00001 201 06 01 01 79 PB603 2 00001 201 06 01 01 80 604 2 00001 201 06 01 01 81 605 2 00001 201 06 01 01 82 606 2 00001 201 06 01 01 83 607 2 00001 201 06 01 01 84 608 2 00001 201 06 01 01 85 609 2 00001 201 06 01 01 8
8. 50V 596 Rad Capacitor Mylar Poly 50V 596 Rad Capacitor Electrolytic 50V 20 Rad Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Capacitor Electrolytic 16V 20 Rad Capacitor Electrolytic 16V 20 Rad Capacitor Electrolytic 50V 20 Rad Capacitor Silver Mica 500V 5 DM15 Capacitor Tantalum 35V 20 Rad Capacitor Electrolytic 25V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Electrolytic 25V 20 Rad Capacitor Tantalum 35V 20 Rad Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Capacitor Electrolytic 16V 20 Rad Capacitor Electrolytic 16V 20 Rad Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c 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 Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Capacitor Polystyrene 50V 5 Ax Cap Polyester Film 50V 5 40 85c Rad Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal F
9. Capacitor Ceramic Disc 50V 1096 SL Capacitor Ceramic Disc 50V 1096 SL Capacitor Ceramic Disc 50V 1096 SL Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Stacked Metal Film 50V 5 40 85c Stacked Metal Film 50V 5 40 85c Stacked Metal Film 50V 5 40 85c Cap Polyester Film 50V 5 40 85c Rad Cap Polyester Film 50V 5 40 85c Rad Cap Polyester Film 50V 5 40 85c Rad Capacitor Ceramic Disc 50V 1096 SL Stacked Metal Film 50V 5 40 85c Cap Polyester Film 50V 5 40 85c Rad Cap Stacked Metal Film 50V 5 40 85c Stacked Metal Film 50V 5 40 85c Stacked Metal Film 50V 5 40 85c Stacked Metal Film 50V 5 40 85c Cap Monolythic Ceramic 50V 2096 Z5U Cap Monolythic Ceramic 50V 2096 Z5U Capacitor Ceramic Disc 50V 1096 SL Capacitor Ceramic Disc 50V 1096 SL Capacitor Electrolytic 50V 20 Rad Capacitor Electrolytic 50V 20 Rad Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Capacitor Ceramic Disc 50V 10 SL SR510
10. Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Comp 1 4W 5 Resistor Metal Film 1 8W 1 50PPM SR510 PARTS LIST REF SRS part VALUE 305 R162 4 00188 407 4 99 306 R163 4 00035 401 10M 307 R165 4 00215 407 909 308 R166 4 00141 407 100 309 R167 4 00215 407 909 310 R168 4 00141 407 100 311 R169 4 00134 407 1 24 312 R170 4 00144 407 107 313 R171 4 00182 407 33 2 314 R172 4 00035 401 10M 315 R173 4 00193 407 499 316 R174 4 00180 407 301 317 R175 4 00165 407 200 318 R176 4 00211 407 9 53 319 R177 4 00130 407 1 00K 320 R178 4 00035 401 10M 321 R201 4 00135 407 1 50K 322 R202 4 00194 407 5 11K 323 R203 4 00138 407 10 0K 324 R204 4 00138 407 10 0K 325 R205 4 00153 407 15 0K 326 R206 4 00138 407 10 0K 327 R207 4 00135 407 1 50K 328 R208 4 00130 407 1 00 329 R209 4 00150 407 13 0K 330 R210 4 00033 404 100M 331 R211 4 00138 407 10 0K 332 R212 4 00135 407 1 50K 333 R213 4 00130 407 1 00K 334 R214 4 0
11. Momentary Push Button Switch Momentary Push Button Switch Momentary Push Button Switch Momentary Push Button Switch Momentary Push Button Switch Momentary Push Button Switch Momentary Push Button Switch Momentary Push Button Switch Momentary Push Button SR510 PARTS LIST REF SRS parti VALUE 101 625 2 00001 201 06 01 01 102 PC1 7 00038 701 SR511 103 R 601 4 00034 401 10K 104 R602 4 00034 401 10K 105 RN601 4 00223 425 22KX7 106 RN602 4 00226 425 150 9 107 RN603 4 00226 425 150 9 108 RN604 4 00221 425 150 5 109 0601 3 00086 340 7211 110 0602 3 00086 340 7211 111 U 603 3 00044 340 74 244 112 U 604 3 00046 340 74 374 113 0605 3 00071 340 CD4030 114 0606 3 00071 340 CD4030 115 U 607 3 00053 340 7415164 116 0608 3 00053 340 7415164 117 0609 3 00053 340 7415164 118 0610 3 00053 340 7415164 119 0611 3 00053 340 7415164 120 0612 3 00053 340 7415164 121 0613 3 00053 340 7415164 122 U614 3 00053 340 7415164 123 Z0 0 00042 010 4 40 HEX 124 Z0 0 00077 030 3 16 X5 16 NYLN 125 Z0 0 00102 042 10 LOCK 126 Z0 0 00104 043 4 NYLON 127 Z0 0 00106 044 CLEAR 128 Z0 0 00111 053 1 3 4 24 129 Z0 0 00112 053 1 3 4 24R 130 Z0 0 00117 053 12 24 131 ZO 0 00128 053 4 24 132 70 0 00129 053 5 24 133 70 0 00132 053 6 1 2 24 134 70 0 00139 054 9 26 X20 135 Z0 0 00203 032 323914 136 Z0 1 00011 130 20 PIN IDP 137 Z0 1 00073 120 INSL 1
12. both ways to enter the offset value When the REL function is turned off using the REL key the offset is turned off but the value is not lost If the manual OFFSET is now turned ON the offset will be that set by the REL function Offset The OFFSET section controls the manual OFFSET The offset is turned ON and OFF using the upper key in the OFFSET section When the offset is ON the lower two keys are used to set the amount of offset A single key press will advance the offset by 0 025 of full scale If the key is held down the offset advances in larger and larger increments the largest increment being 10 of full scale When the offset is turned OFF the applied offset returns to zero but the offset value is not lost The next press of the upper offset key returns to ON sets the offset to the previously entered value If an attempt is made to advance the offset value beyond full scale the OFFSET ON LED will blink An offset up to 1 024 times the full scale sensitivity may be entered When the expand is on this is 10X the full scale output If the REL function is ON when the manual OFFSET is turned ON the REL function is turned OFF but the offset value remains the same The OFFSET keys may now be used to adjust this offset value Note that the offsets either manual offset or those generated by the REL function represent a fraction of the full scale reading and so their absolute value will change when the sensitivity scal
13. largest allowable dc current before overload is 1 uA No current larger than 10 mA should ever be applied to this input The conversion ratio is 106 V A thus the full scale current sensitivities range from 100 fA to 500 nA with a max ac input before overload of 1 uA peak You should use short cables when using the current input Signal Filters There are three user selectable signal filters available a line frequency notch a 2X line frequency notch and an auto tracking bandpass Each of the filters has a pair of indicator LED s and a function key located in the SIGNAL FILTERS section of the front panel Pressing a key will toggle the status of the appropriate filter The status of each filter is displayed as IN filter active or OUT filter inactive The notch filters have a Q of 10 and a depth of at least 50 dB Thus the line frequency notch is 6 Hz wide and the 2X line notch has a width of 12 Hz Both of these filters can increase the dynamic reserve up to 50 dB at the notch frequencies The achievable reserve is limited by the maximum allowable signals at the inputs The notch frequencies are set at the factory to either 50 Hz or 60 Hz The user can adjust these frequencies See the Maintenance and Repair section for alignment details These filters precede the bandpass filter in the signal amplifier The bandpass filter has a Q of 5 and a 6 dB roll off in either direction Thus the pass band between 7096 pass points
14. return to local When using the GPIB interface the REN LLO commands not implemented The command is used by both interfaces to set the remote local status J n1 n2 n3 n4 The J command sets the RS232 end of record characters sent by the SR510 to those specified by the ASCII codes n1 n4 If no argument is included the end of record sequence returns to the default a carriage return otherwise up to four characters may be specified The end of record required by the SR510 when receiving commands is not affected Kn The K command simulates a front panel key press The effect is exactly the same as pressing the selected key once The parameter n is required Key Post Time Constant Up Post Time Constant Down Pre Time Constant Up Pre Time Constant Down Offset Up Offset Down Zero Phase Simultaneous 90 Up Down 8 Line Notch Filter 9 Bandpass Filter 10 Line X 2 Notch Filter 11 Relative Auto Offset 12 Offset On Off 13 Expand 14 Local Display Up when REMOTE 15 Reference Trigger Mode 16 Reference Mode f 2f 17 Degrees Up 18 Degrees Down 19 Quad Up NOOR O ND 15 18 20 Quad Down 21 Select Display f phase 22 Sensitivity Up 23 Sensitivity Down 24 Dyn Res Up 25 Dyn Res Down 26 Display Up 27 Display Down L m n The L command sets and reads the status of the line notch filters If m is 1 then the 1X line notch is selected if m is 2 the 2X line n
15. 1 2 U312 select f or 2f operation This signal is fed back to the phase detector U306 to be compared with the reference output of U304 0315 compares the triangle output with a variable voltage to generate a square wave signal phase shifted from the reference The range of this fine phase shift control is 5 to 95 degrees The output of U315 serves as the reference to a second phase locked loop This second PLL uses a similar proportional tracking triangle VCO Comparator U329 looks at the square wave output of the VCO while comparator U328 detects the zero crossings of the triangle output 1 2 U327 selects one these comparators to feed back to the phase detector U316 Since the square and triangle outputs are in quadrature U327 selects either an in phase or quadrature relationship between the two VCO s Thus the output of the second VCO can be shifted from 5 to 185 deg from the reference 31 The triangle output is divided by R363 and R362 before reaching transconductance amplifier 2 2 U322 The amplitude of the triangle input to this amplifier is enough to just saturate the input and provide a sine wave output 2 2 U325 then amplifies the sine wave before it goes to the demodulator U324 is a comparator which generates a square wave in phase with the sine output 0326 divides the frequency of the square wave by 8 and 2 2 U327 selects the frequency of the square wave chopper Demodulator and Low Pass Amplifier Amplifier U402 an
16. 299 R156 4 00193 407 499 300 R157 4 00180 407 301 301 R158 4 00141 407 100 302 R159 4 00141 407 100 303 R160 4 00033 404 100M 304 R161 4 00204 407 750 56 DESCRIPTION Resistor Carbon Comp 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM 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 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 Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor
17. 340 KBP201G BR 81D 2 BR2 3 00062 340 KBP201G BR 81D 3 6 00001 612 BR 2 3A 2PIN PC 4 C101 5 00069 513 1U 5 C102 5 00069 513 1U 6 C103 5 00038 509 10U 7 C104 5 00008 501 22 8 C105 5 00002 501 100P 9 C 106 5 00008 501 22 10 C107 5 00030 520 22000 11 C108 5 00030 520 22000 12 C110 5 00038 509 10U 13 C111 5 00081 516 1P 14 C116 5 00100 517 2 20 15 C117 5 00035 521 470 16 C118 5 00100 517 2 2U 17 C 120 5 00100 517 2 2U 18 C 121 5 00035 521 470 19 C122 5 00100 517 2 20 20 C 123 5 00060 512 1 0U 21 C124 5 00060 512 1 0U 22 125 5 00030 520 22000 23 C 126 5 00030 520 22000 24 C 127 5 00057 512 22U 25 C 128 5 00057 512 22U 26 C 129 5 00060 512 1 0U 27 C181 5 00060 512 1 0U 28 C132 5 00060 512 1 0U 29 C133 5 00052 512 010 30 C134 5 00052 512 01U 31 C 136 5 00003 501 10 32 C137 5 00003 501 10 33 C145 5 00009 501 24 34 146 5 00009 501 24 35 147 5 00003 501 10 36 C148 5 00017 501 47 37 201 5 00020 501 7 5P 38 C202 5 00109 525 150P 39 C203 5 00048 566 0015U 40 C204 5 00051 512 015U 41 C205 5 00055 512 15U 42 C206 5 00060 512 1 0U 43 C207 5 00059 512 47U 44 C208 5 00003 501 10 45 C209 5 00109 525 150P 46 C210 5 00048 566 0015U 47 C211 5 00051 512 015U 48 C212 5 00055 512 15U 49 C213 5 00060 512 1 0U 51 DESCRIPTION Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Battery Capacitor Mylar Poly
18. 4 MHz CPU The GPIA interrupts the CPU whenever a GPIB transaction occurs which requires the CPU s response The GPIB address is set by switch bank SW1 Power Supplies The line transformer provides two outputs 40VAC and 15VAC both center tapped The transformer has dual primaries which may be selected by the voltage selector card in the fuse holder The 15VAC is rectified by diode bridge BR2 and passed to 5V regulator U909 The output of U909 powers the microprocessor and its related circuitry The 40VAC output is half wave rectified by BR1 and regulated by U901 and U902 to provide 20V and 20V These two dc voltages are then regulated again by 15V regulators U903 U908 Each 15V regulator powers a separate section of the lock in to reduce coherent pick up between sections U911 and U912 provide plus and minus 7 5V and U910 generates 5V for the analog circuits 33 Internal Oscillator The internal oscillator is on a small circuit board attached to the rear panel of the instrument Local regulators Q1 and Q2 provide power to the board The VCO input is internally pulled up by R12 This pulls the VCO input to 10V when the VCO input is left open 2 4 U1 translates the input voltage to provide a negative control voltage to U2 the function generator P3 adjusts the VCO calibration U2 is a sine wave generator whose frequency range is selected by the VCO Range switch and capacitors 4 6 P2 adjusts the sine wave sy
19. 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor 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 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 Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 SR510 PARTS LIST REF SRS parti VALUE 407 R359 4 00045 401 2 0K 408 R360 4 00032 401 100K 409 R361 4 00084 401 5 1K 410 R362 4 00181 407 32 4K 411 R363 4 00132 407 1 10K 412 R364 4 00032 401 100K
20. 5 Auto Offset Out of Range This bit is set if the auto offset function cannot zero the output because the output exceeded 1 024X full scale Bit 6 SRQ This bit is high if the SR510 has generated an SRQ on the GPIB interface This bit is reset after the SR510 has been serial polled This bit is set only for status reads via a serial poll ie Bit 6 always zero for the RS232 Bit 7 Command Error This bit is set when an illegal command string is received Errors Whenever a parameter out of range or an unrecognized command error occurs the appropriate status bits are set and the ERR LED flashes In addition any commands remaining on the current command line up to the next lt cr gt are lost The ERR LED will also light if any of the internal communication buffers overflows This occurs when 240 characters are pending on the command queue or output queue The ERR LED will go off as soon as all buffers drop below 200 characters again Reset The Z command resets the unit to its default state The default front panel settings are listed in the DEFAULTS section of the Guide to Operations In addition the interface status returns to LOCAL the SRQ mask is cleared the RS232 character WAIT interval is set to 6 and the terminating sequence is reset to the proper defaults The command and output buffers are cleared by the Z command Therefore it is bad practice to use the Z command before all previous commands have been
21. Note that not all dynamic reserve settings are allowed at every sensitivity E n If nis 1 the E command turns the output expand on If n is 0 the expand is turned off If n is absent the expand status is returned F The F command reads the reference frequency For example if the reference frequency is 100 Hz the F command returns the string 100 0 If the reference frequency is 100 0 kHz the string 100 0 3 is returned The F command is a read only command G If nis included the G command sets the gain sensitivity If n is absent the gain setting is returned n Sensitivity 1 10 nV 2 20 nV 3 50 nV 4 100 nV 5 200 nV 6 500 nV 7 1 uV 8 2 uV 9 5 uV 16 1 mV 17 2 mV 18 5 mV 19 10 mV 20 20 mV 21 50 mV 22 100 mV 23 200 mV 24 500 mV Note that sensitivity settings below 100 nV are allowed only when a pre amplifier is connected H The H command reads the pre amplifier status If a pre amplifier is connected a 1 is returned otherwise a 0 is returned The H command is a read only command l If n is included the command sets the remote local status If n is absent the remote local status is returned Status IS O Local all front panel keys are operative 1 Remote front panel keys are not operative The display up key returns the status to local 2 Lock out front panel keys are not operative No key returns the status to local Another command is needed to
22. Socket THRU HOLE Switch DIP Switch DIP Switch Rocker PCB Mount LHS of 510 Switch Rocker PCB Mount RHS of 510 Transformer SRS sub assemblies SRS sub assemblies Integrated Circuit Thru hole Pkg Transistor TO 92 Package Transistor TO 92 Package Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg SR510 PARTS LIST REF SRS parti VALUE 560 U118 3 00130 340 5532A 561 U201 3 00087 340 LF347 562 0202 3 00093 340 LM13600 563 U 203 3 00073 340 CD4052 564 0204 3 00073 340 CD4052 565 U 205 3 00076 340 09211 566 U 206 3 00038 340 74HC139 567 0207 3 00038 340 74HC139 568 U 208 3 00087 340 LF347 569 U301 3 00088 340 LF353 570 0303 3 00076 340 09211 571 U304 3 00094 340 LM311 572 0305 3 00075 340 CD4538 573 U 306 3 00072 340 CD4046 574 0307 3 00093 340 LM13600 575 U308 3 00066 340 CA3140E 576 U309 3 00093 340 LM13600 577 U310 3 00076 340 09211 578 031 3 00076 340 09211 579 0312 3 00076 340 09211 580 0313 3 00049 340 74 74 581 0314 3 00094 340 LM311 582 315 3 00094 340 LM311 583 U316 3 00072 340 CD4046 584 U317 3 00093 340 LM13600 585 U318 3 000
23. Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Electrolytic 16V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c 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 SR510 PARTS LIST REF SRS part VALUE 101 C 410 5 00056 512 1U 102 C411 5 00056 512 1U 103 C 412 5 00056 512 1U 104 C 413 5 00049 566 0010 105 414 5 00053 512 0330 106 415 5 00072 513 100 107 C416 5 00056 512 1U 108 C417 5 00060 512 1 0U 109 C418 5 00052 512 01U 110 C419 5 00052 512 01U 111 C 420 5 00049 566 001U 112 C421 5 00013 501 113 C422 5 00013 501 114 C501 5 00012 501 330P 115 C 502 5 00136 519 01U 116 C503 5 00007 501 220P 117 C504 5 00002 501 100 118 C 505 5 00008 501 22P 119 C 506 5 00054 512 0470 120 507 5 00054 512 0470 121 508 5 00054 512 0470 122 509 5 00054 512 0470 123
24. an example of the new techniques used in the SR510 consider the harmonic rejection problem Previously lock in amplifiers used a PLL with a square wave output The Fourier components of the square wave created a serious problem the lock in would respond to signal and noise at f 3f 5f ad infinitum Quite often one component of this picket fence of frequencies would land on fs le ly fr DIGITAL INPUTS PLL FREQUENCY OVERLOAD INDICATOR UNLOCK INDICATOR AUTO TRACKINC BANDPASS FILTER HICH CAIN A C AMPLIFIER INAL MONITOR OUTPUT D omur LOW PASS FILTER LOW PASS FILTER CHOPPER STABILIZED 1mS X05 15615 D C AMPLIFIER 2 OUTPUT LOW PASS FILTER LOW PASS FILTER CHOPPER STABILIZED 1m 1005 150415 D C AMPLIFIER ANALOC CONTROLS PHASE SHIFT SIGNAL OFFSET REAR PANEL D A TRACKING BANDPASS AND PANEL METERS RATIO OUTPUTS ANALOG MULTIPLEXER MAGNITUDE OUTPUT AND S H AMPLIFIER PHASE OUTPUT FRONT PANEL some noise source giving a spurious result To overcome this difficulty designers employed tuned amplifiers or heterodyning techniques All of these fix ups had drawbacks including phase amplitude errors susceptibility to drift and card swapping to change frequencies In contrast the SR510 detects the signal by mixing a reference sine wave in a precision analog multiplier Because of the low harmonic content of this sine wave the instrument is insens
25. from local to remote 5 The IFC Interface Clear line clears the bus of all data and activity Though GPIB is a very powerful interface strict protocol must be observed for it to operate successfully Appendix D Program Examples All of the program examples which follow do the same thing only the computer language or interface is changed The programs read the Channel 1 and 2 Outputs and write the results to the computer screen In addition the X6 analog output port is ramped from 0 to 10V Program Example 1 IBM PC Basic via RS232 In this example the IBM PC s ASYNC port known as COM1 or AUX to DOS users will be used to communicate with the SR510 Only two wires between the IBM PC s ASYNC port and the SR510 are needed pins 2 amp of the RS232 but pins 5 6 8 and 20 should be connected together on the connector at the IBM end 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 EXAMPLE USING IB ON THE R AND ALL OTH PROGRAM TO REA PC BASICA AN EAR PANEL OF T ER SWITCHES D THE COMI IN SW2 UP D THE SR510 OUTPUT AND RAMP TH HE SR510 S RS232 PORT E X6 ANALOG OUTPUT ET SWITCH 1 OF SW2 DOWN 9600 BAUD NO PARITY 2 STOP BITS
26. impedance of 1KQ R128 The input current is converted to voltage by R135 and the op amp Q103 bootstraps out the summing junction capacitance of Q102 Notch Filters U107 is a high Q line frequency notch filter which can be switched in and out by analog switch 1 4 U106 The frequency and depth of the filter can be adjusted with P102 and P103 Resistors R146 R149 and switch U108 make up a selectable attenuator U118 is a line frequency 2nd harmonic notch filter selected by 2 4 U106 P104 and P105 adjust the frequency and depth The second notch filter has a gain of 3 and its output is scaled by U110 and resistors R156 R159 The signal then takes two paths to inverting amplifier 0111 and to the input of the tracking bandpass filter U111 has the same gain as the bandpass filter The output of either U111 or the bandpass filter is selected by 3 4 U112 and 4 4 U106 and amplified by 0113 U114 U115 provide a last stage of gain and scaling and the final output is ac coupled and buffered by 4 4 U208 Bandpass Filter The bandpass filter is a three op amp state variable active filter 3 4 of U201 make up the three op amps of the standard filter U203 U204 and U205 are analog switches which select the feedback capacitors for the 5 decades of operation The two halves of U202 are matched transconductance amplifiers operating as programmable voltage controlled current sources which take the place of the normal frequency sett
27. of istray 3 installing capacitive shielding by placing both the experiment and the detector in a metal box 37 Inductive Coupling Here noise couples to the experiment via a magnetic field Detector Expermnent Hz Power Circuit Inductive Noise Coupling A changing current in a nearby circuit gives rise to a changing magnetic field which induces an emf in the loop connecting the detector to the experiment emf d dt This is like a transformer with the experiment detector loop as the secondary winding Cures for inductively coupled noise include 1 removing or turning off the interfering noise source difficult to do if the noise is a broadcast station 2 reduce the area of the pick up loop by using twisted pairs or coaxial cables or even twisting the 2 coaxial cables used in differential hook ups 3 using magnetic shielding to prevent the magnetic field from inducing an emf at high frequencies a simple metal enclosure is adequate 4 measuring currents not voltages from high impedance experiments Resistive Coupling or Ground Loops Currents through common connections can give rise to noise voltages Experiment Ground Bus Power Cireult Resistive Coupling Here the detector is measuring the voltage across the experiment plus the voltage due to the noise current passing through the finite resistance of the ground bus This problem arises because we have used two diffe
28. over the RS 232 and IEEE 488 interfaces In addition to simply reading data from the lock in the computer can control all of the instrument settings with simple ASCII commands A key feature of the instrument is its four A D inputs and two D A outputs These analog I O ports may be used to read and supply analog voltages to an experiment or measurement All of the input and output ports have a full scale range of 10 24VDC with 2 5 mV resolution and 0 05 accuracy Computer control can eliminate set up errors reduce tedium and allow more complete data recording and post measurement analysis Also the computer can play an active role in the data acquisition by adjusting gains etc in response to changing measurement conditions The microprocessor based design eliminates many analog components to improve performance reliability and reduce cost Each unit is computer calibrated at the factory and calibration constants are placed in the instrument s read only memory The SR510 has only one fifth of the analog trimming components that are found in older designs Creative programming on the user s part can extend the instrument s capabilities For example the lab computer can instruct the lock in to measure the signal at zero and ninety degrees of phase Doing so allows both the amplitude and phase of the signal of interest to be measured Circuit Description Introduction The SR510 Lock in amplifier is an integrated instrum
29. status byte sent by the SR510 when it is serial polled is the same status byte which is read using the Y command except for bit 6 SRQ Of course when the SR510 is serial polled it does not encode the status byte as a decimal number The SR510 can be programmed to generate a service request SRQ to the GPIB controller every time a given status condition occurs This is done using the V n command The mask byte n 0 255 is the SRQ mask byte The mask byte is always logically anded with the status byte If the result is non zero the SR510 generates an SRQ and leaves the status byte unchanged until the controller performs a serial poll to determine the cause of the service request When the unit has been serial polled the status byte is reset to reflect all of the status conditions which have occurred since the SRQ was generated For example if we want to generate an SRQ whenever there is an overload or unlock condition we need an SRQ mask byte equal to 00011000 binary or 24 decimal V24 command The byte 00011000 binary corresponds to the status byte with the no reference and unlock status bits set If an overload occurs then an SRQ will be generated The serial poll will return a status byte showing SRQ and overload If an unlock condition occurs before the serial poll is concluded another SRQ will be generated as soon as the serial poll is finished A second serial poll will reflect the unlock condition Any SRQ gene
30. the source bias voltage small while providing enough signal for the lock in to measure The Auto Tracking Bandpass Filter has a Q of 5 and follows the reference frequency The passband is therefore 1 5 of the reference frequency The bandpass filter can provide an additional 20 dB of dynamic reserve for noise signals at frequencies outside the passband The filter also improves the harmonic rejection of the lock in The second harmonic is attenuated an additional 13dB and higher harmonics are attenuated by 6 dB octave more You may wish to use the bandpass filter and select a low dynamic reserve setting in order to achieve a better output stability Since the processor can only set the bandpass filter s center frequency to within 1 of the reference frequency this filter can contribute up to 5 of phase shift error and up to 596 of amplitude error when it is used In addition the bandpass filter adds a few nanovolts of noise to the front end of the instrument when it is in use Line Notch Filters should be used in most measurement situations The filters will reject about 50 dB of line frequency noise about a factor of 300 If your reference frequency is one octave away then these filters will introduce a 10 phase shift error and a few percent amplitude error Their effect on your signal is negligible if your reference frequency is more than two octaves away The frequency range of the SR510 lock in amplifier extends from 0 5Hz
31. to accept data When every listener is ready the line goes high and the talker may release data to the bus After data is on the bus the talker pulls the DAV Data Valid line down At this point each listener retrieves the data Before and during the retrieval of the data the listener holds the NDAC No Data Accepted line down When every listener has received the data the NDAC line goes high allowing the talker to release the DAV line high Finally the listener pulls down the NDAC line until another transfer is initiated 41 Data Bus There are eight data lines which use negative logic and pass the bits of each byte in parallel General Interface Lines These five lines operate independently of the handshake lines and use negative logic 1 The EOI End or Identify line is used by the talker to designate the end of message 2 The SRQ Service Request line is used by any device to ask for service The controller can serial poll each device each device returns an 8 bit status byte to determine who needs attention It can also do a parallel poll using the EOI and lines where each device is assigned a single data line 3 The ATN Attention line makes both talkers and listeners accept information and passes control of the DAV line to the controller This line is used by the controller to identify talkers and listeners through their addresses 4 The REN Remote Enable line changes the status of an instrument
32. unit to wait nX4 mS before sending each character over the RS232 bus The command WO sets the wait interval to zero and results in the fastest transmission The wait interval is set to 6 24 mS on power up Termination Sequences The default RS232 termination characters are sufficient to interface with most computers however it will occasionally be necessary to send special terminating sequences to fit the requirements of some computers This can be done with the J command The format for the command is J n1 n2 n3 n4 where n1 n2 n3 and n4 are decimal values between 0 and 255 corresponding to the decimal ASCII codes of the desired termination characters For instance if the desired termination sequence is an asterisk ASCII 42 two carriage returns ASCII 13 and a line feed ASCII 10 the appropriate command is J 42 13 13 10 If G command is sent requiring an answer of 24 sensitivity 500 mV the SR510 would respond with the string 24 cr cr Ift 22 Up to four terminating characters may be specified by the J command If no arguments are sent with the J command the terminating sequence returns to the default echo on lt cr gt lt If gt echo off lt cr gt The J command does not affect the terminating character cr required at the end of commands received by the SR510 It also does not affect the terminating sequence sent with data over the GPIB interface The SR510 with the
33. up 2400 up up down 1200 down up down 600 up down down 300 Bit Setting Explanation 4 up Odd parity down Even parity 5 up No parity down Parity enabled 6 up No echo for computer down Echo mode for terminal 7 up Two stop bits down One stop bit 8 unused Eight data bits are always sent regardless of the parity setting The most significant bit is always Zero Example Bit 1 down and all others up for RS232 communication at 9600 baud no parity two stop bits and no echo or prompts by the SR510 SR510 Guide to Operation Front Panel The front panel has been designed to be almost self explanatory The effect of each keypress is usually reflected in the change of a nearby LED indicator or by a change in the quantity shown on a digital display This discussion explains each section of the front panel proceeding left to right Signal Inputs There are three input connectors located in the SIGNAL INPUT section of the front panel The rocker switch located above the B input selects the input mode either single ended A differential or current The A and B inputs are voltage inputs with 100 MQ 25 pF input impedance Their connector shields are isolated from the chassis ground by 100 These inputs are protected to 100V dc but the ac input should never exceed 10V peak The maximum ac input before overload is 1V peak The I input is a current input with an input impedance of 1 KO to a virtual ground The
34. 0 92 C401 5 00060 512 1 0U 93 C 402 5 00052 512 01U 94 403 5 00052 512 010 95 404 5 00060 512 1 00 96 405 5 00060 512 1 00 97 406 5 00052 512 010 98 407 5 00052 512 010 99 408 5 00003 501 10 100 409 5 00056 512 10 52 DESCRIPTION Stacked Metal Film 50V 5 40 85c Stacked Metal Film 50V 5 40 85c Stacked Metal Film 50V 5 40 85c Capacitor Electrolytic 50V 20 Rad Capacitor Electrolytic 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 Capacitor Ceramic Disc 50V 10 SL Capacitor Polystyrene 50V 5 Ax Capacitor Electrolytic 50V 20 Rad Cap Stacked Metal Film 50V 5 40 85c Cap Polyester Film 50V 5 40 85c Rad Cap Stacked Metal Film 50V 5 40 85c 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 Electrolytic 50V 20 Rad Cap Stacked Metal Film 50V 5 40 85c Cap Polyester Film 50V 5 40 85c Rad Cap Stacked Metal Film 50V 5 40 85c Cap Polyester Film 50V 5 40 85c Rad Capacitor Ceramic Disc 50V 10 SL Capacitor Ceramic Disc 50V 10 SL Capacitor Electrolytic 25V 20 Rad Capacitor Electrolytic 25V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor
35. 0 DG528 625 U508 3 00087 340 LF347 626 U509 3 00076 340 09211 627 U510 3 00076 340 09211 628 U511 3 00087 340 LF347 629 0512 3 00087 340 LF347 630 U513 3 00087 340 LF347 631 0514 3 00094 340 LM311 632 0515 3 00087 340 LF347 633 0516 3 00076 340 09211 634 0517 3 00092 340 LH0071 635 U 701 3 00132 340 Z80A CPU 636 0703 3 00081 341 2 8 100 637 0704 3 00491 340 UPD71054C 638 U705 3 00037 340 74HC138 639 U 706 3 00037 340 74HC138 640 U707 3 00037 340 74 138 641 0708 3 00040 340 74 157 642 U 709 3 00049 340 74 74 643 U710 3 00045 340 74HC32 644 0711 3 00051 340 74HCU04 645 U712 3 00047 340 74HC4040 646 0713 3 00049 340 74 74 647 U714 3 00042 340 74 175 648 U715 3 00042 340 74 175 649 U716 3 00044 340 74 244 650 0717 3 00046 340 74 374 651 U718 3 00039 340 74 14 652 0719 3 00046 340 74 374 653 U 720 3 00046 340 74 374 654 U 721 3 00046 340 74 374 655 U722 3 00045 340 74HC32 656 0801 3 00493 340 UPD71051C 657 0802 3 00111 340 68488 658 0803 3 00044 340 74 244 659 804 3 00044 340 74 244 660 0805 3 00049 340 74 74 661 0806 3 00109 340 1488 63 DESCRIPTION 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 I
36. 01 1 0 31 R16 4 00079 401 4 7 32 R17 4 00104 401 82K 33 R18 4 00034 401 10K 34 R19 4 00034 401 10K 35 R20 4 00188 407 4 99 36 R21 4 00188 407 4 99 37 R22 4 00022 401 1 0M 38 R23 4 00022 401 1 0M 39 R24 4 00031 401 100 40 R25 4 00031 401 100 41 SW1 2 00013 215 DPDT 42 SW2 2 00013 215 DPDT 43 U1 3 00087 340 1 347 44 U2 3 00085 340 1 18038 45 03 3 00118 325 78L15 46 U4 3 00124 325 79L15 47 Z0 0 00100 040 1 4 1 16 48 70 0 00122 053 2 1 4 24 49 70 0 00136 053 8 1 2 24 Miscellaneous Parts List NO REF SRS part VALUE 1 ZO 7 00204 720 SR500 35 2 U702 3 00161 342 27128 150 3 20 0 00045 013 4 40 MINI 4 20 0 00078 031 4 40 1 M F 5 70 0 00167 023 6 32X1 2RP 6 ZO 0 00179 000 RIGHT FOOT 7 ZO 0 00180 000 LEFT FOOT 8 ZO 0 00185 021 6 32X3 8PP 9 ZO 0 00187 021 4 40 1 4 10 ZO 0 00204 000 REAR FOOT 11 ZO 0 00209 021 4 40 3 8 12 Z0 0 00247 026 6 32 1 4 TRUSSP 13 Z0 0 00248 026 10 32X3 8TRUSSP 14 Z0 0 00371 026 4 40X3 16PF 15 ZO 6 00054 611 375A 3AG 16 Z0 7 00147 720 BAIL 17 Z0 7 00198 720 58510 23 18 Z0 7 00199 720 SR510 24 19 Z0 7 00200 720 SR510 25 20 20 7 00203 720 SR500 34 66 DESCRIPTION Resistor Carbon Film 1 4W 596 Resistor Carbon Film 1 4W 596 Resistor Carbon Film 1 4W 596 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 196 Resistor Metal Film 1 8W 196
37. 0150 407 13 0K 335 R215 4 00033 404 100M 336 R216 4 00032 401 100K 337 R217 4 00032 401 100K 338 R218 4 00035 401 10M 339 R219 4 00032 401 100K 340 R220 4 00177 407 3 48 341 R221 4 00039 401 120K 342 R222 4 00096 401 62K 343 R223 4 00039 401 120K 344 R224 4 00094 401 6 8K 345 R225 4 00063 401 3 0K 346 R226 4 00094 401 6 8K 347 R227 4 00063 401 3 0K 348 R228 4 00021 401 1 0K 349 R229 4 00021 401 1 0K 350 R301 4 00034 401 10K 351 R302 4 00138 407 10 0K 352 R303 4 00138 407 10 0K 353 R304 4 00045 401 2 0K 354 R305 4 00032 401 100K 355 R306 4 00021 401 1 0K 57 DESCRIPTION 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 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 Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1
38. 0199 407 6 81 373 R324 4 00199 407 6 81K 374 R325 4 00163 407 2 80 375 R326 4 00150 407 13 0K 376 R327 4 00159 407 2 10K 377 R328 4 00029 401 1 8K 378 R329 4 00088 401 51K 379 R330 4 00021 401 1 0K 380 R332 4 00161 407 2 49 381 R333 4 00029 401 1 8K 382 R334 4 00197 407 6 49 383 R335 4 00088 401 51K 384 R336 4 00021 401 1 0K 385 R337 4 00035 401 10M 386 R338 4 00030 401 10 387 R339 4 00032 401 100K 388 R340 4 00032 401 100K 389 R341 4 00025 401 1 2M 390 R342 4 00073 401 330K 391 R343 4 00046 401 2 0 392 R344 4 00069 401 300K 393 R345 4 00022 401 1 0M 394 R346 4 00021 401 1 0K 395 R347 4 00021 401 1 0K 396 R348 4 00021 401 1 0K 397 R349 4 00069 401 300K 398 R350 4 00093 401 6 2K 399 R351 4 00138 407 10 0K 400 R352 4 00032 401 100K 401 R353 4 00034 401 10K 402 R354 4 00203 407 75 0K 403 R355 4 00187 407 4 53 404 R356 4 00160 407 2 26K 405 R357 4 00163 407 2 80 406 R358 4 00034 401 10K 58 DESCRIPTION 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 Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1
39. 05 LO 01 f QO MN I5 Post Time Constant m 2 none 0 1 S 1S N OI5 U m n The 0 command sets and reads the unit s ROM calibration bytes m is the address offset of the byte 0 255 If n is absent the value of the addressed calibration byte is returned If n is included the addressed calibration byte is set to the value of n 0 255 The new value will be in effect until the power is turned off or a reset command is issued Use of this command is not recommended V n If n is included the V command sets the GPIB SRQ service request mask to the value n If n is absent the value of the SRQ mask is returned W n The W command sets and reads the RS232 character wait interval If n is included the SR510 will wait n 4 mS between characters sent over the RS232 interface This allows slow computer interfaces to keep up n can range from 0 to 255 If n is absent the wait value is returned The wait interval is set to 6 on power up Xn v n designates one of the 6 general purpose analog ports located on the rear panel If nis 1 2 3 or 4 the X command will return the voltage on the designated analog input port X1 X4 in volts If n is 5 or 6 then v may also be sent If v is included the designated analog output port X5 or X6 will be set to v volts where v has the range 10 24V to 10 24V If v is absent the output value of the selected port is returned On power up port X5 i
40. 10 effectively increasing the full scale sensitivity by 10 The ouptut impedance is 1 and the output current is limited to 20 mA The analog meter always displays the OUTPUT voltage Accuracy is 296 of full scale The OUTPUT LCD display provides a read out of the displayed parameter in real units The scale of the displayed quantity is indicated by the three scale LED s to the right of the display This read out auto ranges and will reflect the sensitivity added when the EXPAND function is on Expand The output EXPAND is toggled by pressing the key in the EXPAND section The expand status is indicated by the X10 expand on and the X1 expand off LED s REL Function The relative auto zero function is toggled by the key in the REL section Every time the rel status LED is turned ON the offset value is set to minus the value of the X output thus zeroing the X output This function will work even if X is not the currently displayed parameter If the output is greater than 1 024 times full scale the REL function will not be able to zero the output and the ON LED will blink The offset value will then be set to its max value If NOISE is being displayed when the REL function is turned on the noise ouptut will require a sew seconds to settle again If the manual OFFSET in ON when the REL function is turned on the manual OFFSET will be turned OFF before the auto zero is done The REL function and the manual OFFSET are
41. 10 530 544 U 101 8 00085 860 SR513 ASSY 545 U102 8 00085 860 SR513 ASSY 546 0103 3 00076 340 09211 547 0104 3 00118 325 78115 548 0105 3 00124 325 79115 549 0106 3 00076 340 09211 550 U 107 3 00130 340 5532 551 108 3 00076 340 09211 552 U 109 3 00088 340 LF353 558 U110 3 00076 340 09211 554 0111 3 00089 340 LF357 555 0112 3 00076 340 09211 556 113 3 00089 340 LF357 557 0114 3 00076 340 09211 558 U115 3 00089 340 LF357 559 0117 3 00088 340 LF353 61 DESCRIPTION Resistor Carbon Film 1 4W 596 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 596 Resistor Carbon Film 1 4W 596 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 596 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 Comp 1 2W 596 Resistor Carbon Comp 1 2W 596 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 Comp 1 2W 596 Resistor Carbon Comp 1 2W 596 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 Comp 1 2W 596 Resistor Carbon Comp 1 2W 596 Resistor Network DIP 1 4W 296 8 Ind Resistor Network SIP 1 4W 296 Common Resistor Network SIP 1 4W 296 Common
42. 34 401 10K 503 R546 4 00034 401 10K 504 R547 4 00042 401 15K 505 R548 4 00054 401 200K 506 R549 4 00032 401 100K 507 R701 4 00031 401 100 508 R702 4 00079 401 4 7K 60 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 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor 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 0 1 25ppm Resistor Metal Film 1 8W 0 1 25ppm 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 Resisto
43. 38 Z0 1 00145 131 20 PIN DIF POL 139 Z0 7 00294 710 SR510 27 140 Z0 7 00308 709 SR510 141 Z0 9 00554 913 INDIRECT MFG 142 Z0 9 00815 924 DBL SIDED 1 2 69 DESCRIPTION Switch Momentary Push Button Printed Circuit Board Resistor Carbon Film 1 4W 596 Resistor Carbon Film 1 4W 596 Resistor Network SIP 1 4W 296 Common Resistor Network SIP 1 4W 296 Common Resistor Network SIP 1 4W 296 Common Resistor Network SIP 1 4W 296 Common 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 re wa 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 Nut Hex Spacer Washer lock Washer nylon Window 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 24 UL1007 Strip 1 4x1 4 Tin Wire 24 UL1007 Strip 1 4x1 4 Tin Wire 24 UL1007 Strip 1 4x1 4 Tin Wire 26 UL1061 Termination Connector Male Connector BNC Connector Female Front Panel Lexan Overlay MISC EXPENSE ITEMS QUICK FIX Tape All types
44. 3AG 232 P 101 4 00006 440 20 233 102 4 00012 441 20 234 103 4 00012 441 20 235 104 4 00013 441 50K 236 105 4 00014 441 5K 237 P 401 4 00011 441 10K 238 402 4 00011 441 10K 239 P 403 4 00011 441 10K 240 P 404 4 00011 441 10K 241 P501 4 00002 440 100 242 P502 4 00002 440 100 243 PC1 7 00036 701 SR500 244 Q101 3 00016 323 2 6485 245 Q102 3 00016 323 2 6485 246 Q103 3 00031 325 MPSA18 247 Q201 3 00887 325 MPS2907A 248 Q202 3 00026 325 2 5210 249 Q 502 3 00026 325 2 5210 250 Q 701 3 00026 325 2 5210 251 Q702 3 00026 325 2 5210 252 Q703 3 00026 325 2 5210 253 R101 4 00033 404 100 55 DESCRIPTION Crystal Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Diode Fuse Trim Pot Single Turn In Line Leads Pot Multi Turn Trim 3 8 Square Top Ad Pot Multi Turn Trim 3 8 Square Top Ad Pot Multi Turn Trim 3 8 Square Top Ad Pot Multi Turn Trim 3 8 Square Top Ad Pot Multi Turn Trim 3 8 Square Top Ad Pot Multi Turn Trim 3 8 Square Top Ad Pot Multi Turn Trim 3 8 Square Top Ad Pot Multi Turn Trim 3 8 Square Top Ad Trim Pot Single Turn In Line Leads Trim Pot Single Turn In Line Leads Printed Circuit Board Transistor TO 71 Package Transistor TO 71 Package Transistor TO 92 Package Transistor TO 92 Package Tran
45. 413 R365 4 00045 401 2 0K 414 R366 4 00021 401 1 0K 415 R367 4 00151 407 130K 416 R368 4 00156 407 16 2K 417 R369 4 00130 407 1 00K 418 R370 4 00130 407 1 00 419 R371 4 00030 401 10 420 R372 4 00023 401 1 1M 421 R373 4 00033 404 100M 422 R374 4 00033 404 100M 423 R375 4 00033 404 100M 424 R376 4 00033 404 100M 425 R377 4 00187 407 4 53 426 R378 4 00045 401 2 0K 427 R401 4 00217 408 1 000 428 R402 4 00217 408 1 000 429 R403 4 00085 401 5 1M 430 R404 4 00217 408 1 000 431 R405 4 00217 408 1 000 432 R406 4 00193 407 499 433 R407 4 00130 407 1 00 434 R408 4 00131 407 1 00 435 R409 4 00022 401 1 0M 436 R410 4 00217 408 1 000 437 R411 4 00193 407 499 438 R412 4 00217 408 1 000 439 R413 4 00203 407 75 0K 440 R414 4 00080 401 47 441 R415 4 00142 407 100K 442 R417 4 00034 401 10K 443 R418 4 00132 407 1 10K 444 R419 4 00179 407 30 1K 445 R420 4 00183 407 348K 446 R 421 4 00155 407 150K 447 R422 4 00184 407 37 4K 448 R423 4 00212 407 9 76 449 R424 4 00161 407 2 49K 450 R425 4 00021 401 1 0K 451 R426 4 00045 401 2 0K 452 R427 4 00131 407 1 00 453 R428 4 00131 407 1 00 454 R429 4 00146 407 110K 455 R430 4 00140 407 10 2K 456 R431 4 00032 401 100K 457 R432 4 00021 401 1 0K 59 DESCRIPTION Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resis
46. 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Comp 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Comp 1 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 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 Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 SR510 PARTS LIST REF SRS parti VALUE 356 R307 4 00040 401 13K 357 R308 4 00193 407 499 358 H 309 4 00073 401 330 359 R310 4 00021 401 1 0K 360 R311 4 00021 401 1 0K 361 R312 4 00021 401 1 0K 362 R313 4 00034 401 10K 363 R314 4 00069 401 300K 364 R315 4 00099 401 680K 365 R316 4 00099 401 680 366 R317 4 00093 401 6 2K 367 R318 4 00138 407 10 0K 368 R319 4 00034 401 10K 369 R320 4 00034 401 10K 370 R321 4 00032 401 100K 371 R322 4 00170 407 249K 372 R323 4 0
47. 6 610 2 00001 201 06 01 01 87 PB611 2 00001 201 06 01 01 88 612 2 00001 201 06 01 01 89 613 2 00001 201 06 01 01 90 614 2 00001 201 06 01 01 91 615 2 00001 201 06 01 01 92 616 2 00001 201 06 01 01 93 617 2 00001 201 06 01 01 94 618 2 00001 201 06 01 01 95 619 2 00001 201 06 01 01 96 620 2 00001 201 06 01 01 97 621 2 00001 201 06 01 01 98 PB622 2 00001 201 06 01 01 99 623 2 00001 201 06 01 01 100 624 2 00001 201 06 01 01 68 DESCRIPTION LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LCD Display LCD Display Analog Meter Switch Momentary Push Button Switch Momentary Push Button Switch Momentary Push Button Switch Momentary Push Button Switch Momentary Push Button Switch Momentary Push Button Switch Momentary Push Button Switch Momentary Push Button Switch Momentary Push Button Switch Momentary Push Button Switch Momentary Push Button Switch Momentary Push Button Switch Momentary Push Button Switch Momentary Push Button Switch Momentary Push Button Switch
48. 60 Hz iMHz 100 MHz Frequency 1 GHz Noise Spectrum Some of the non essential noise sources appear in this spectrum as spikes on the intrinsic background There are several ways which these noise sources work their way into an experiment Capacitive Coupling voltage on a nearby piece of apparatus or operator can couple to a detector via a stray capacitance Although Cstray may be very small the coupled in noise may still be larger than a weak experimental signal Siray Capacitance 60 Hz Power Circuit Detector Experiment Capacitive Noise Coupling To estimate the noise current through C into the detector we have stray Cstray dV jWOstrayVnoise dt where a reasonable approximation to Cstray can be made by treating it as parallel plate capacitor Here w is the radian frequency of the noise source perhaps 2 x 60Hz Vnoise is the noise voltage source amplitude perhaps 120 VAC For an area of A 01 m and a distance of d 0 1m the capacitor will have a value of 0 009 pF and the resulting noise current will be 400pA This meager current is about 4000 times larger than the most sensitive current scale that is available on the SR510 lock in Cures for capacitive coupling of noise signals include 1 removing or turning off the interfering noise source 2 measuring voltages with low impedance sources and measuring currents with high impedance sources to reduce the effect
49. 611 3 00012 306 GREEN 23 DS612 3 00012 306 GREEN 24 DS613 3 00012 306 GREEN 25 DS614 3 00012 306 GREEN 26 DS615 3 00012 306 GREEN 27 05616 3 00012 306 GREEN 28 05617 3 00012 306 GREEN 29 DS618 3 00012 306 GREEN 30 DS619 3 00012 306 GREEN 31 05620 3 00012 306 GREEN 32 05621 3 00012 306 GREEN 33 DS622 3 00012 306 GREEN 34 05623 3 00012 306 GREEN 35 05624 3 00012 306 GREEN 36 05625 3 00012 306 GREEN 37 DS626 3 00012 306 GREEN 38 05627 3 00012 306 GREEN 39 DS628 3 00012 306 GREEN 40 05629 3 00012 306 GREEN 41 05630 3 00012 306 GREEN 42 DS631 3 00012 306 GREEN 43 DS632 3 00012 306 GREEN 44 DS633 3 00012 306 GREEN 45 05634 3 00012 306 GREEN 46 DS635 3 00012 306 GREEN 47 DS636 3 00012 306 GREEN 48 DS637 3 00012 306 GREEN 49 05638 3 00013 306 RED 67 DESCRIPTION Capacitor Ceramic Disc 50V 1096 SL Capacitor Ceramic Disc 50V 1096 SL Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Monolythic Ceramic 50V 20 Z5U Diode Diode Diode Diode LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular LED Rectangular
50. 7 22 WHITE 706 Z0 0 00227 052 17 22 RED 707 ZO 0 00228 052 17 22 GREEN 708 ZO 0 00231 043 4 SHOULDER 709 ZO 0 00233 000 HANDLE1 710 ZO 0 00241 021 4 40 3 16 711 20 0 00249 021 6 32 1 1 2 712 20 0 00256 043 6 SHOULDER 64 DESCRIPTION Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Transistor TO 92 Package Transistor TO 92 Package Integrated Circuit Thru hole Pkg Voltage Regulator TO 3 Metal Can Voltage Regulator TO 3 Metal Can Voltage Reg TO 220 TAB Package Voltage Reg TO 220 TAB Package Voltage Reg TO 220 TAB Package Voltage Reg TO 220 TAB Package Voltage Reg TO 220 TAB Package Voltage Reg TO 220 TAB Package Integrated Circuit Thru hole Pkg Transistor TO 92 Package Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Heat Sinks Power Entry Hardware Hardware Misc Power Entry Hardware Insulators Lugs Nut Kep Nut Kep Screw Sheet Metal Standoff Termination Tie Washer Flat Washer Split Wire 18 UL1007 Stripped 3 8x3 8 No Tin Wire 24 UL1007 Strip 1 4x1 4 Tin Wire 18 UL1007 Stripped 3 8x3 8 No Tin Wire 24 UL1007 Strip 1 4x1 4 Tin Wire 18 UL1007 Stripped 3 8x3 8 No Tin Wire 24 UL1007 Strip 1 4x1 4 Tin Grommet Screw Panhead Phillips Screw Panhead Phillips Insulators Screw Panhead Phillips Wire 22 UL1007 Wire 22 UL1007 Wire 22 UL1007 Wire 22 UL1007 Washer nylon Hardware Misc Screw
51. 76 340 09211 586 U319 3 00066 340 CA3140E 587 0320 3 00076 340 09211 588 0321 3 00066 340 CA3140E 589 0322 3 00093 340 LM13600 590 0323 3 00093 340 LM13600 591 0324 3 00094 340 LM311 592 0325 3 00091 340 LF412 593 0326 3 00068 340 CD4018 594 0327 3 00076 340 09211 595 0328 3 00094 340 LM311 596 U 329 3 00094 340 LM311 597 U401 3 00076 340 09211 598 U 402 3 00091 340 LF412 599 U 403 3 00090 340 LF411 600 U404 3 00106 340 LT1007 601 0405 3 00074 340 CD4066 602 0406 3 00057 340 534 603 U 407 3 00090 340 LF411 604 0408 3 00106 340 LT1007 605 U 409 3 00090 340 LF411 606 U410 3 00084 340 7650 607 0411 3 00126 335 51A05 608 0412 3 00126 335 51A05 609 0413 3 00126 335 51A05 610 0414 3 00126 335 51A05 62 DESCRIPTION Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg Integrated Circuit Thru hole Pkg 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 Ci
52. BJ found on the SR565 disk These routines allow for simple interfacing to the SR510 at 19 2 kbaud from C programs include lt stdio h gt Compile with gt MSC program name AL link with RS232 0BJ SR565 disk RS232 0BJ defines init To use these routines the large model must be used Compile with the AL switch and link with RS232 OBJ Only two wires between the IBM PC s ASYNC port and the SR530 are needed pins 2 amp of the RS232 but pins 5 6 8 and 20 should be connected together on the connector at the IBM end Initializes 1 to 19 2 kbaud txstr str Ghar str str must terminate with char Sends string str to COMI rxstr str str must be declared with 15 characters or more length Fills str wit h string received from COMI If an error occurs your procedure nocom is called Nocom must be a C procedure i Output using Microsoft C v3 0 large Set all switches in SW2 to UP on SR51 22 char str1 20 str2 20 float vl x init 3 2 init COM1 txstr w0 set charac x 0 while 1 txstr q read chann rxstr strl into strl sscanf strl Sf amp vl s 45 n your program Example program to read the SR510 outputs and ramp the x6 analog model and the COMI port 0 for 19 2 kbaud port to 19 2 kbaud ter interval to 0 el 1 output can strl for a float variable x 0 0025 incre
53. BW is set using the keys below the ENBW indicator LED s same keys as used to set the POST filter The PRE filter keys do nothing in this case Pressing the upper key when the bandwidth is already 1 Hz will reset the rms noise average output to zero restarting the calculation Likewise with pressing the lower key when 10 Hz is already selected The noise is the rms deviation of the output within a 1 or 10 Hz equivalent noise bandwidth about the reference frequency A dc output does not contribute to the noise the noise is determined only by the ac wiggles at the output By measuring the noise at different frequencies the frequency dependence of the noise density be found This usually has the form of Vnoise 1 f The noise computation assumes that the noise has a Gaussian distribution such as Johnson noise Since the computation takes many time constants reciprocal bandwidth the noise output should be allowed to approach a steady value before a reading is taken For the 1 Hz ENBW this time is on the order of 15 to 30 seconds for the 10 Hz ENBW the output stabilizes much faster The noise output will vary slightly since there will always be noise variations that are slow compared to the bandwidth Any DC component in the output will not contribute to the noise However a large DC output will cause the noise computation to initially rise to a large value before approaching the final answer As a result the computati
54. E 488 GPIB interface built in The GPIB address is set using SW1 located to the right of the interface connectors Refer to page 7 for switch setting details RS232 Connector The SR530 has an RS232 interface The connector is configured as a DCE The baud rate parity stop bits and echo mode are selected using SW2 located to the right of the interface connectors Refer to Page 7 for switch setting qetails Signal Monitor Output This BNC provides the buffered output of the signal amplifiers and filters This is the signal just before the demodulator The output impedance is lt 10 When a full scale input is applied the to peak amplitude at this output is 20 mV 200 mV or 2 V for dynamic reserve settings of high norm and low respectively Preamp Connector This 9 pin D connector provides power and control signals to external peripherals such as pre amplifiers The available power is described below Pin Voltage Current Available 1 20 100 mA 2 5 10mA 6 20 100 mA A Signal ground Digital ground General Purpose A D and D A There are four analog input ports labeled X1 through X4 These inputs may be digitized and read via the computer interfaces The range is 10 24 V to 410 24 V and the resolution is 2 5 mV The input impedance is 1 MO A digitization can be performed in about 3 mS but the result may take longer to transmit over the interface being used There are two analog output ports labe
55. Full Scale Return Preamp Status 1 installed Return the Remote Local Status Select Local Front panel active Select Remote Front panel inactive Select Remote with full lock out Set RS232 End of Record to cr Set End of record to n m o p Simulates Key press of button 1 see un abridged command list Simulates Key press of button 32 Return Status of Line Notch Filter Remove Line Notch Filter Insert Line Notch Filter Return Status of 2XLine Filter Remove 2XLine Notch Filter Insert 2XLine Notch Filter Return the f 2f Status Set reference mode to f Set reference mode to 2f RO R2 S0 S2 T1 T1 1 T1 11 T2 T2 0 T2 1 2 2 Return the ENBW setting Select 1 Hz ENBW Select 10 Hz ENBW Return Offset Status Turn off Offset Turn on Offset v offset Return the Phase Setting Set the Phase to v Abs v lt 999 deg Return the value shown on the Output LCD Return the trigger mode Set the trigger for rising edge Set the trigger for zero crossing Set the trigger for falling edge Return the display status Display X Acos Display Offset setting Display Noise Return pre filter setting Set the pre filter TC to 1 mS Set the pre filter TC to 100 S Return the post filter setting Remove post filter Set the post filter TC to 0 1 S Set the post filter TC to 1 0 S Return the value of the SRQ mask Set the SRQ Mask to the value n See the Status Byte definition Return the RS232 wait interv
56. GPIB Interface For a brief introduction to the GPIB standard please read Appendix C at the back of this manual Before using the GPIB interface you must set the switches in SW1 per the instructions on page 7 GPIB Capabilities The GPIB capabilities of the SR510 consistent with IEEE standard 488 1978 are shown in the table below Also shown are the responses of the SR510 to some standard commands Code Function SH1 Source handshake capability AH1 Acceptor handshake capability T5 Basic Talker Serial Poll Unaddressed to talk if addressed to listen L4 Basic Listener Unaddressed to listen if addressed to talk SR1 Service request capability PPO parallel poll capability DC1 Device Clear capability RLO REN LLO GTL not implemented l command sets Remote Local SR510 Response to GPIB Commands Mnemonic Command Response DCL Device Clear Same as Z command SDC Selected Same as Z command Device Clear SPE Serial Poll Send Status Byte Enable amp clear status byte Because the SR510 can be controlled by an RS232 interface as well as the GPIB the remote local functions are not standard There is no local with lock out state When in the local state remote commands are processed even without the REN command being issued This is because the RS232 interface has no provision for bus commands and remote commands over the RS232 interface would never be enabled Serial Polls and Service Requests The
57. HE SR510 OUTPUT AND RAMP THE X6 ANALOG OUTPUT 20 USING IBM PC BASICA AND THE CAPITAL EQUIPMENT CORP GPIB INTERFACE CARD 30 40 50 ON THE SR510 REAR PANEL SET SWITCHES 4 AND 6 ON SW1 TO DOWN DEVICE 60 ADDRESS 23 RS232 ECHO ON AND SWITCH 1 ON SW2 TO DOWN RS232 BAUD 70 RATE 9600 ALL OTHER SWITCHES SHOULD BE UP 80 NOTE THAT THE RS232 ECHO IS FOR DEBUGGING AND DEMOSTRATION PURPOSES 90 UNDER NORMAL CONDITIONING SWITCH 6 OF SW1 SHOULD BE UP SINCE THE RS232 100 ECHO SLOWS DOWN THE GPIB INTERFACE TLO 120 DEF SEG amp HC000 BASE ADDRESS OF CEC CARD 130 0 TRANSMIT 3 RECV 6 ADDRESSES OF CEC FIRM WARE ROUTINES 140 ADDR 21 SYS 0 CONTROLLER ADDRESS 150 INZ IFC UNT UNL MTA LISTEN 23 DATA Z 13 160 170 QS IFC MTA LISTEN 23 DATA Q 13 180 X6 IFC MTA LISTEN 23 DATA X6 190 LISNS IFC UNT UNL MLA TALK 23 200 2102 220 CALL INIT ADDR SYS INIT X6 OUTPUT TO ZERO 230 CALL TRANSMIT INZS STATUS RESET SR510 240 GOSUB 540 CHECK TRANSMIT STATUS 250 260 X 0 X6 OUTPUT TO ZERO NAE 280 CALL TRANSMIT 05 5 05 READ OUTPUT 290 GOSUB 540 300 GOSUB 450 GET RESULT 310 V1 VAL ANSS INTO V1 320 330 340 PRINT OUTPUT V1 350 360 X X 0025 INCREMENT X6 OUTPUT BY 2 5 MV 370 IF X gt 10 THEN X 0 RESET RAMP 380 XS 65 STRS X 13 MAKE X6 COMMAND STRING 47 LH 390 CALL TRANSMIT X STATUS SET NEW X6
58. HOUT LOCK OUT the DISPLAY UP key will return the instrument to LOCAL front panel control If the instrument is the REMOTE WITH LOCK OUT state no front panel key will return the status to LOCAL In this case a RETURN TO LOCAL command must be sent over the computer interface or the power must be turned off and back on 12 Defaults If the REL key is held down when the POWER is turned on the instrument settings will be set to the defaults shown below instead of the settings in effect when the power was turned off Parameter Setting BANDPASS OUT LINE OUT LINE X 2 OUT SENSITIVITY 500 mV DYN RES LOW DISPLAY X EXPAND OFF REL OFF OFFSET OFF value 0 PRE TIME CONSTANT 100 mS POST TIME CONSTANT 0 1 S ENBW 1Hz REFERENCE MODE f TRIGGER MODE SYMMETRIC REFERENCE DISPLAY FREQUENCY PHASE 0 Whenever default values are used at power up the red ERR LED will turn on for about 3 seconds If the ERR LED is on when the instrument is powered on without the LOCAL key down then the instrument is ignoring the retained settings This can be due to a low battery SR510 Guide to Operation Rear Panel AC Power The ac line voltage selector card line fuse and line cord receptacle are located in the fuse holder at the left side of the rear panel See the section Preparation for Use at the front of this manual for instructions on setting the ac voltage selector and choosing the correct fuse GPIB Connector The SR530 has an IEE
59. I Terminal Before attempting any detailed programming with the SR510 it is best to try out the commands using a terminal Connect a terminal with an RS232 port to the RS232 connector on the rear panel of the SR510 Set the baud rate parity and stop bits to match the terminal by setting SW2 per the switch setting table given on page 7 The echo mode should be enabled switch 6 DOWN After setting SW2 and connecting the terminal hold down the REL key while turning the unit on This causes the SR510 to assume its default settings so that the following discussion will agree with the actual responses of the SR510 The ACT and ERR LED s on the front panel will flash for a second and the sign on message will appear on the terminal Following the message the prompt OK gt will be displayed This indicates that the SR510 is ready to accept commands Type the letter P followed by a carriage return P lt cr gt The SR510 responds by sending to the terminal the characters 0 00 indicating that the phase is set to 0 degrees In general a command with no arguments or parameters reads a setting of the unit To set the phase to 45 degrees type the command P45 cr To see that the phase did change use the SELECT key on the front panel to display the phase on the REFERENCE DIGITAL DISPLAY Typing the phase read command P lt cr gt will now return the string 45 00 16 to the terminal Now read the gain using the sensitivity read comma
60. MODEL SR510 LOCK IN AMPLIFIER RS Stanford Research Systems 1290 D Reamwood Avenue Sunnyvale CA 94089 U S A Phone 408 744 9040 Fax 408 744 9049 Email info thinkSRS com www thinkSRS com Copyright 1985 1987 1989 2003 2013 Stanford Research Systems Inc All Rights Reserved Revision 3 4 11 2013 TABLE OF CONTENTS Condensed Information SAFETY and Preparation for use Symbols Specifications Front Panel Summary Abridged Command List Status Byte Definition Configuration Switches Guide to Operation Front Panel Signal Inputs Signal Filters Sensitivity Dynamic Reserve Status Indicators Display Select Output Expand Function Rel Function Offset Time Constants Noise Measurements Reference Input and Trigger Levels Phase Controls Power Switch Local Remote Operation Default Settings Rear Panel AC Power GPIB IEEE 488 Connector RS232 Interface Signal Monitor Output Pre Amp Connector A D Inputs and D A Outputs Ratio Feature Internal Oscillator Guide to Programming Communications Command Syntax Status LED s RS232 Echo Feature Try out with an ASCII Terminal Command List Status Byte Errors Reset Command Trouble Shooting Interface Problems Common Hardware Problems Common Software Problems L L O 01 QO N O O OO CO RS232 Interface Introduction to the RS232 Data Communications Equipment Wait Command Termination Sequence GPIB 488 Interface
61. PARTS LIST REF SRS parti VALUE 152 C714 5 00014 501 390 158 C801 5 00012 501 330P 154 C802 5 00012 501 330P 155 C803 5 00012 501 330P 156 C804 5 00052 512 01U 157 C805 5 00052 512 01U 158 C806 5 00100 517 2 2U 159 C807 5 00100 517 2 2U 160 C808 5 00100 517 2 20 161 C 809 5 00100 517 2 2U 162 C810 5 00010 501 270P 163 C901 5 00100 517 2 20 164 C 902 5 00100 517 2 2U 165 C903 5 00100 517 2 20 166 C904 5 00100 517 2 2U 167 C905 5 00100 517 2 20 168 C 906 5 00100 517 2 2U 169 C907 5 00100 517 2 2U 170 C908 5 00100 517 2 20 171 QC 909 5 00100 517 2 20 172 910 5 00100 517 2 20 173 911 5 00100 517 2 20 174 912 5 00100 517 2 20 175 C913 5 00035 521 470 176 914 5 00035 521 470 177 915 5 00100 517 2 20 178 916 5 00100 517 2 20 179 917 5 00100 517 2 20 180 918 5 00100 517 2 20 181 919 5 00035 521 470 182 920 5 00035 521 470 183 923 5 00192 542 220 MIN 184 924 5 00100 517 2 20 185 925 5 00046 510 25000 186 926 5 00046 510 25000 187 C927 5 00192 542 220 MIN 188 928 5 00192 542 220 MIN 189 929 5 00034 526 1000 190 930 5 00034 526 1000 191 931 5 00034 526 1000 192 932 5 00034 526 1000 193 933 5 00103 524 1 00 194 934 5 00103 524 1 00 195 935 5 00036 522 68000 196 936 5 00056 512 10 197 C937 5 00056 512 1U 198 C 938 5 00100 517 2 20 199 C 939 5 00100 517 2 2U 200 801 1 00014 160 9 PIN D 201 802 1 00016 160 R
62. Panhead Phillips Screw Panhead Phillips Washer nylon IL I are wa SR510 PARTS LIST REF SRS part VALUE 713 ZO 0 00371 026 4 40 3 16 714 20 0 00500 000 554808 1 715 20 0 00521 048 3 18 716 20 0 00526 048 10 1 2 18 717 20 0 00893 026 8 32 3 8 718 20 1 00003 120 719 20 1 00010 130 20 PIN ELH 720 Z0 1 00029 150 TO 3 721 Z0 1 00053 172 USA 722 ZO 7 00197 720 SR510 20 723 ZO 7 00201 720 SR500 32 724 Z0 7 00202 720 SR500 33 725 Z0 7 00205 720 SR510 26 726 Z0 9 00188 917 SR510 530 SER 727 ZO 9 00215 907 1 16 BLACK 728 ZO 9 00216 907 1 8 BLACK 729 ZO 9 00217 907 3 16 BLACK Internal Oscillator PCB Parts List REF SRS part VALUE 1 C1 5 00023 529 1U 2 C2 5 00023 529 1U 3 C3 5 00102 517 4 70 4 C4 5 00054 512 0470 5 C5 5 00087 516 390P 6 C6 5 00102 517 4 70 7 C7 5 00014 501 390P 8 C8 5 00034 526 1000 9 C9 5 00100 517 2 2U 10 C10 5 00034 526 1000 11 C11 5 00100 517 2 2U 12 P1 4 00016 445 10K 13 P2 4 00003 440 100K 14 4 00016 445 10K 15 PC1 7 00037 701 SR501 16 R1 4 00079 401 4 7K 17 R2 4 00083 401 47K 18 R3 4 00202 407 698 19 R4 4 00189 407 41 2 20 R5 4 00186 407 4 22 21 R6 4 00190 407 42 2K 22 R7 4 00186 407 4 22 23 R8 4 00202 407 698 24 R9 4 00078 401 39K 25 R10 4 00186 407 4 22 26 R11 4 00022 401 1 0 27 12 4 00042 401 15K 28 R13 4 00070 401 30K 29 R14 4 00034 401 10K 65 DESCRIPTION Sc
63. S232 25 PIN D 202 803 1 00238 161 SHIELDED 54 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 Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Ceramic Disc 50V 10 SL Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Electrolytic 25V 20 Rad Capacitor Electrolytic 25V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Electrolytic 25V 20 Rad Capacitor Electrolytic 25V 20 Rad Cap Mini Electrolytic 50V 20 Radial Capacitor Tantalum 35V 2096 Rad Capacitor Electrolytic 50V 2096 Ax Capacitor Electrolytic 50V 20 Ax Cap Mini Electrolytic 50V 20 Radial Cap Mini Electrolytic 50V 20 Radial Capacitor Electrolyti
64. This signal can be either the lock in output or one of the four independent analog inputs buffered by U501 These general purpose inputs are located on the rear panel of the instrument The selected signal is sampled and held on capacitor C502 and buffered by 4 4 U508 The A D conversion is done by successive approximation using comparator U514 to compare the sampled and held signal with known outputs of U505 a 12 bit DAC with a precision reference Note that the output of U506 an 8 bit DAC is summed with the output of U505 This 8 bit DAC corrects for offset errors which can accumulate as analog voltages pass through buffers S H amps comparators These offsets are measured after each unit is manufactured and values to compensate for these offsets are placed in the unit s ROM The polarity of the offset corrected 12 bit DAC is set by 2 4 U511 and the SIGN bit yielding 13 bits of resolution from 10 24 to 410 24 volts D A s In addition to providing reference voltages for A D conversion the DAC output voltage may be multiplexed by U507 to one of eight sample and hold amplifiers which provide analog output and control voltages The microprocessor refreshes each S H amplifier every few milliseconds to prevent droop Two of these outputs are available as general programmable outputs on the rear panel Two are used to program the band pass filer and the reference oscillator phase shift One output is subtracted from the lock in ou
65. VOLTAG 400 GOSUB 540 410 420 GOTO 280 LOOP FOREVER 430 440 GET AN ANSWER STRING FROM THE SR510 450 CALL TRANSMIT LISN STATUS MAKE SR510 TALKER 460 GOSUB 540 470 ANSS SPACES 10 INIT ANSWER STRING 480 CALL RECV ANSS LENGTHSSTATUSS READ RESULT INTO ANS 490 GOSUB 540 500 RETURN 510 520 530 CHECK STATUS OF LAST TRANSMISSION FOR ERRORS 540 IF 5 05 0 THEN RETURN STATUS OKAY 550 PRINT STATUS CODE STATUS ON GPIB ERROR 560 STOP 48 Program Example 5 HP85 via GPIB This program provides an example of an HP85 program using the GPIB interface which could be used to control the lockin amplifier In this example the SR510 should be addressed as device 16 by setting the switch bank SW1 per the instructions Page 7 10 30 40 50 70 80 x 0 OUT ENT ER 716 DIS X IF OUT GOT P OUTP X pu gt 10 716 0 20 PUT 716 O 2 V1 E 02 5 EN 0 x6 X 49 Documentation This section contains the parts lists and schematics for the SR510 lock in amplifier The first digit of any part number can be used to locate the scematic diagram for the part For example R415 is located on sheet 4 of the schematic diagrams 50 SR510 PARTS LIST Main Assembly PCB Parts List REF SRS part VALUE 1 BR1 3 00062
66. X10 Set the Offset to null the output subsequent readings are relative readings Enables or Disables Offset and allows any offset up to full scale to be entered Pre filter has time constants from 1 mS to 100 S 6 dB Octave Post filter has time constants of 0 0 1 or 1 0 S 6 dB Octave Equivalent Noise Bandwidth Specifies the bandwidth when making Noise measurements 1Hz or 10 Hz ENBW 1 Input 0 5 Hz to 100 KHz 100 mV minimum Trigger on rising edge zero crossing or falling edge PLL can lock to either X1 or X2 of the reference input frequency Adjust phase in smoothly accelerating 0 025 steps or by 90 steps Press both 90 buttons to zero the phase Display reference phase setting or reference frequency Instrument settings from the last use are recalled on power up En En 0 1 Jn m 0 p K1 K32 L1 L1 0 L1 1 L2 L2 0 L2 1 MO M1 Abridged Command List Return the REL Status Turn the REL off Turn the REL on Return Bandpass Filter Status Take out the Bandpass Filter Put in the Bandpass Filter Return the Reference LCD Status Display the Reference Frequency Display the Reference Phase Shift Return Dynamic Reserve Setting Set DR to LOW range Set DR to NORM range Set DR to HIGH range Return Expand Status Turn Expand off Turn Expand on Return the Reference Frequency Return the Sensitivity Setting Select 10 nV Full Scale G1 G3 with SRS preamp only Select 500 mV
67. al Set RS232 wait interval to nX4mS Return the voltage at the rear panel analog port n n from 1 to 6 Set analog port 5 to voltage v Set analog port 6 to voltage v Return the Status Byte value Test bit n of the Status Byte Reset to default settings and cancel all pending command Status Byte Definition Bit Meaning 0 Magnitude too small to calculate phase Command Parameter is out of range No detectable reference input PLL is not locked to the reference Signal Overload Auto offset failed signal too large SRQ generated Unrecognized or illegal command 01 O N Configuration Switches There are two banks of 8 switches SW1 and SW2 located on the rear panel SW1 sets the GPIB address SW2 sets the RS232 parameters The configuration switches are read continuously and any changes will be effective immediately SW1 GPIB Mode Switches Bit Example Function 1 up GPIB Address Switches 2 up Address 0 to 30 allowed 3 up up for bit 1 4 down down for bit 0 5 up Most Significant Bit 6 down down to echo RS232 normally up 7 up Not Used 8 up Not Used If the GPIB mode switches are set as shown in the example column above then the lockin will be addressed as GPIB device 23 and all GPIB commands and data will be echoed over the RS232 for de bugging purposes SW2 RS232 Mode Switches Bit 1 Bit2 Bit3 Baud Rate up up up 19200 down up up 9600 up down up 4800 down down
68. al considerations in deciding how to operate the lock in amplifier Dynamic Reserve DR is the ratio of the largest noise signal that the lock in can tolerate before overload to the full scale input Dynamic reserve is usually expressed in dB Thus a DR of 60 dB means that noise source 1000 times larger than a full scale input can be present at the input without affecting the measurement of the signal A higher DR results in a degraded output stability since most of the gain is DC gain after the phase sensitive detector In general the lowest DR which does not cause an overload should be used The Current Input has 1 input impedance and a current gain of 106 Volts Amp Currents from 500 nA down to 100 fA full scale can be measured The impedance of the signal source is the most important factor to consider in deciding between voltage and current measurements For high source impedances gt 1 MQ or small currents use the current input Its relatively low impedance greatly reduces the amplitude and phase errors caused by the cable capacitance source impedance time constant The cable capacitance should still be kept small to minimize the high frequency noise gain of the current preamplifier For moderate source impedances or larger currents the voltage input is preferred A small value resistor may be used to shunt the source The lock in then measures the voltage across this resistor Select the resistor value to keep
69. ar all previous conditions especially after a power up or after settings have been changed The definitions for each bit of the status byte are given below Bit 0 Busy When this bit is set it indicates the SR510 has unprocessed commands pending on its command queue For RS232 communications this bit is always high since the Y command itself will be an unprocessed command This bit is not reset when read but only when there are no pending commands Since the SR510 buffers incoming commands it is not necessary to read this bit before sending each command Commands received while the SR510 is executing a previous command are stored until all previously received commands have been executed Bit 1 Command Parameter Out of Range This bit is set if a parameter associated with a command is not in the allowed range Bit 2 No Reference This bit is set when no reference input is detected either because the amplitude is too low or the frequency is out of range Bit 3 Unlock This bit is set when the reference oscillator is not locked to the reference input If there is no reference input bit 2 no reference will be set but bit 3 unlock may not be Bit 4 20 Overload This bit is set if there is a signal overload This can happen when the sensitivity is too high the dynamic reserve is too low the offset is on or the expand is on Overloads on the general purpose A D inputs or the ratio output are not detected Bit
70. c 35V 20 Rad Capacitor Electrolytic 35V 20 Rad Capacitor Electrolytic 35V 20 Rad Capacitor Electrolytic 35V 20 Rad Capacitor Tantalum 50V 20 Rad Capacitor Tantalum 50V 20 Rad Cap Electro 25V 10 Ax Mallory TCX Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Capacitor Tantalum 35V 20 Rad Capacitor Tantalum 35V 20 Rad Connector D Sub Right Angle PC Female Connector D Sub Right Angle PC Female Connector IEEE488 Reverse R A Female SR510 PARTS LIST REF SRS parti VALUE 203 CY1 6 00010 620 4 000 MHZ 204 D101 3 00004 301 1 4148 205 D 102 3 00004 301 1 4148 206 D 103 3 00004 301 1 4148 207 D 104 3 00004 301 1 4148 208 D 105 3 00004 301 1 4148 209 D 106 3 00004 301 1 4148 210 D201 3 00004 301 1 4148 211 D202 3 00004 301 1 4148 212 D203 3 00004 301 1 4148 213 D 204 3 00004 301 1 4148 214 D301 3 00004 301 1 4148 215 D 302 3 00004 301 1 4148 216 D303 3 00004 301 1 4148 217 D401 3 00004 301 1 4148 218 D 402 3 00004 301 1 4148 219 D 403 3 00004 301 1 4148 220 D 404 3 00004 301 1 4148 221 D 501 3 00004 301 1 4148 222 502 3 00004 301 134148 223 D 701 3 00007 301 1 747 224 D 702 3 00203 301 1N5711 225 D 703 3 00203 301 1N5711 226 D 704 3 00004 301 1 4148 227 D901 3 00003 301 1 4007 228 902 3 00003 301 1 4007 229 D 903 3 00003 301 1 4007 230 D 904 3 00003 301 1 4007 231 FU1 6 00004 611 1
71. cuit Thru hole Pkg Integrated Circuit Thru hole Pkg SR510 PARTS LIST REF SRS VALUE 662 U807 3 00110 340 1489 663 U 808 3 00078 340 DS75160A 664 0809 3 00117 325 78L12 665 0810 3 00123 325 79L12 666 081 3 00079 340 0575161 667 0901 3 00095 331 LMG317K 668 0902 3 00099 331 LM337K 669 0903 3 00114 329 7815 670 0904 3 00114 329 7815 671 U 905 3 00114 329 7815 672 0906 3 00120 329 7915 673 U907 3 00120 329 7915 674 0908 3 00120 329 7915 675 U 909 3 00113 340 7805 676 0910 3 00116 325 78105 677 U911 3 00096 340 LM317L 678 0912 3 00100 340 LM337L 679 70 0 00004 007 SR510 680 70 0 00014 002 644 681 70 0 00016 000 682 70 0 00017 002 5 683 70 0 00019 003 684 70 0 00025 005 3 8 685 70 0 00043 011 4 40 686 70 0 00048 011 6 32 687 70 0 00064 027 6 20 5 8 688 70 0 00079 031 4 40 3 16 M F 689 70 0 00084 032 36154 690 70 0 00089 033 4 691 70 0 00095 040 4 FLAT 692 70 0 00096 041 4 SPLIT 693 70 0 00114 050 10 1 8 18 694 70 0 00117 053 12 24 695 70 0 00130 050 5 5 8 18 696 70 0 00132 053 6 1 2 24 697 70 0 00135 050 7 5 8 18 698 70 0 00136 053 8 1 2 24 699 70 0 00153 057 GROMMET2 700 ZO 0 00185 021 6 32 3 8 701 ZO 0 00187 021 4 40X1 4PP 702 ZO 0 00207 003 5 703 70 0 00222 021 6 32 1 4 704 Z0 0 00225 052 17 22 BLACK 705 Z0 0 00226 052 1
72. cy 500 ppm C stability Front Panel Summary Signal Inputs Signal Filters Sensitivity Dynamic Reserve Status Indicators Display Select Analog Meters Output LCD s Output BNC s Expand REL Offset Time Constants ENBW Reference Input Reference Trigger f 2f Mode Phase Controls Reference LCD Power Switch Single Ended A True Differential A B or Current 1 Bandpass Q of 5 Auto tracking filter In or Out Line Notch Q of 10 Notch Filter at line frequency In or Out 2XLine Notch Q of 10 Notch Filter at twice line frequency In or Out Full scale sensitivity from 100 nV to 500 mV RMS for voltage inputs or from 100 fA to 500 nA RMS for current inputs Select Dynamic Reserve Stability Sensitivity Ranges LOW 20 dB 5 ppm 1 uV to 500 mV NORM 40 dB 50 ppm 100 nV to 50 mV HIGH 60 dB 500ppm 100nV to5mV OVLD Signal Overload UNLK PLL is not locked to the reference input ERR Illegal or Unrecognized command ACT RS232 GPIB interface Activity REM Remote mode front panel has been locked out X Signal Amplitude at the selected phase 50 OFST Display the offset which is being added to the signal output NOISE Compute and display the noise on the signal Displays Signal Offset or Noise as a fraction of full scale Displays Signal Offset or Noise in absolute units Output follows Analog Meter 10 V for full scale Multiplies the Analog Meter and Output voltage by a factor X1 or
73. d DYN RES to HIGH The PRE TIME CONSTANT should be set to 1mS and the POST TIME CONSTANT to NONE Connect the scope to the OUTPUT on the front panel Set the scope to 2V div and 5mS div Externally trigger the scope using the reference input signal After about 60 seconds the scope display should show a 500 Hz sine wave on a 30 Hz 500 16 Hz square wave Remove the 4 screws holding the top panel on Slide the top panel back about half way Using a small screwdriver adjust P402 at location D2 to minimize the 500 Hz output Adjust P403 at location C2 to minimize the 30 Hz output 34 Now set the both time constants to 1S Adjust P404 at location F4 to zero the output This adjustment has a range of 20 of full scale on the HIGH dynamic reserve setting 2 on NORM and 0 2 on LOW This zeroes the DC output of the unit on all dynamic reserve ranges Replace the top panel Amplifier and Filter Adjustments This section describes how to adjust the Common Mode Rejection and Line notch filter frequencies An oscilloscope and a signal generator which can provide an accurate line frequency and twice line frequency signal are required Allow the unit to warm up for about 1 hour Reset the unit by turning it off and back on while holding the REL key down Remove the 4 screws holding down the top panel Slide the panel back about halfway CMRR Set the reference frequency to 100 Hz lt is convenient to use the SYNC output of the si
74. d switch U401 select the polarity of the reference sine wave This allows phase shifts up to 360 degrees from the reference input The sine wave is ac coupled by U403 and inverted by 0404 U405 selects alternating polarities of the sine wave at the chopper frequency 1 2 or 1 16 This chopped sine wave is then multiplied by the output of the signal amplifiers by the analog multiplier U406 The synchronous output of the multiplier that corresponds to the in phase signal is a square wave at the chopper frequency The output is ac coupled by U407 to remove the dc offset of the multiplier U408 inverts the signal and U405 chops the square wave to recover a dc output U409 buffers the chopper output before the first low pass time constant Op amps U416 and 2 2 U402 make up the first low pass amplifier with relays U411 U415 and U417 selecting the time constant The second low pass amplifier is U419 Analog switch U418 selects the time constant and gain The full scale output of U418 is 5 volts Analog Output and Control The dc output of the demodulator low pass amplifiers is passed to the reference input of multiplying DAC U502 The DAC is programmed with the appropriate attenuation to calibrate the overall gain of the lock in Every gain setting in each dynamic reserve is calibrated independently and the proper attenuations are stored in the unit s ROM A D s Analog multiplexer U504 selects the signal to be digitized by the microprocessor
75. d up by the shield will also appear on the center conductor This is good because the lock in s 100 dB CMRR will reject most of this common mode noise However not all of the noise can be rejected especially the high frequency noise and so the lock in may overload on the high sensitivity ranges Experiment Lock In Amplifier Grounds may be at Different Potentials Quasi Differential Connection The second method of connecting the experiment to the lock in is called the true differential mode Here the lock in uses the difference between the center conductors of the A amp B inputs as the input signal Both of the signal sources are shielded from spurious pick up With either method it is important to minimize both the common mode noise and the common mode signal Notice that the signal source is held near ground potential in both cases A signal which appears on both the A amp B inputs will not be perfectly cancelled the common mode rejection ratio CMRR specifies the degree of cancellation For low frequencies the CMRR of 100 dB indicates that the common mode signal is canceled to 1 part in 109 but the CMRR decreases by about 6 dB octave 20 dB Decade starting at 1KHz Even with a CMRR of 105 a 10 mV common mode signal behaves like 100nV differential signal Experiment Lack In Amplifier Di Ana Grounds may ba at Potentials True Differential Connection 26 There are some addition
76. e is changed A signal which has been nulled by an offset will not be nulled when the sensitivity scale is changed The analog meter and the output BNC indicate the same value given by the equation 10 Vout 10 where Ae 1or 10 per the Expand setting Ay 1 Sensitivity Vi magnitude of the signal phase between signal amp reference Vos Offset fraction of FS lt 1 024 Time Constant There are two post demodulator low pass filters labeled PRE and POST The PRE filter precedes the POST filter in the output amplifier Each filter provides 6 dB oct attenuation The PRE filter time constant ranges from 1 mS to 100 S and is selected by the two keys below the PRE filter indicator LED s Holding down either key will advance the time constant twice a second in the desired direction The POST filter time constant can be set to 1 S or 0 1 S or can be removed altogether NONE using the two keys below the ENBW indicators When set to NONE the total attenuation is that of the PRE filter or 6 dB oct When the POST filter is 1 S or 0 15 the total attenuation is 12 dB oct for frequency components beyond the larger of the POST and PRE filter bandwidths reciprocal time constant Noise When the DISPLAY is set to NOISE none of the PRE and POST indicator LED s are on Instead one of the two ENBW indicators will be on showing the Equivalent Noise Bandwidth of the rms noise calculation The EN
77. e other half of U101 maintains a virtual null between the drains of the two transistors and thus an identical current flows through R110 Any input that would cause a differential between the two drains is amplified by 1 2 U101 and fed back via R112 in such a way as to reduce that differential Since the two transistors are at equal and constant currents their gate source potentials are constant Thus the fed back signal which appears at the source of the right hand transistor exactly matches the input Likewise this signal will match the input to the left hand transistor but with the opposite sign Resistors R112 and R110 attenuate the fed back signal from the output of U101 resulting in a differential input single ended output fixed gain of 10 amplifier P101 adjusts the current balance 30 between the two transistors and therefore their gain match and common mode rejection The output of the pre amp is scaled by resistors R119 R122 and analog switch U103 which make up a 1 2 5 10 attenuator The signal is then amplified by 2 2 U102 Input overload is sensed through diodes D101 D104 Current Amplifier When the input selector is set to current the input to the pre amp comes from the output of the current to voltage converter 1 2 U102 U102 is a low voltage noise bipolar op amp Q102 serves as an input buffer to provide low current noise to the input The op amp always maintains a null at the gates of Q102 thus providing an input
78. e standard defines the format for data transmission the electrical specifications for the signal levels and the mechanical dimensions of connectors Despite the definition of a standard there are so many permutations of control lines data formats and transmission speeds that getting two RS232 devices to communicate usually requires some work In this section we will provide some basic information to aid you in connecting your RS232 device to the SR510 Computer Interface CASE 1 The Simplest Configuration DEVICE DEVICE B In this case one wire is used to send data from device A to device B and another wire is used to send data from device B to device A Notice that pin 2 is an output on device A and an input on device B It is good practice to run the ground pin 7 between the devices as well The RS232 defines two types of devices DTE Data Terminal Equipment and DCE Data Communications Equipment An RS232 port on a computer may be either a DTE or DCE but nearly every terminal with an RS232 port is a DTE RS232 ports on a computer which are intended to connect to a modem such as the COM1 port on the IBM PC are DTE The SR530 is configured as DCE and so it may be directly connected to ASCII terminals and to the COM ports on IBM PC s and compatibles As an example consider connecting an RS232 ASCII computer terminal to the SR510 using a 2 wire link The terminal is a DTE and the SR510 is a DCE T
79. e the frequency or period of the reference oscillator U709 provides a gate pulse to counter 0 Multiplexer U708 selects whether the gate is a single period of the reference period measurement or a gate of known duration frequency measurement Counter 1 is a programmable divide by N counter whose output is either counted for one period of the reference or generates the gate pulse during which reference pulses are counted I O addresses are decoded by U705 U706 and U707 The microprocessor controls the lock in functions through I O ports U714 U721 U713 generates an interrupt to the CPU every 4 msec to keep the microprocessor executing in real time RS232 Interface The RS232 interface uses an 8251A UART U801 to send and receive bytes in a bit serial fashion Any standard baud rate from 300 to 19 2K baud may be selected with the configuration switches The X16 transmit and receive clock comes from counter 2 of U704 The RS232 interface is configured as DCE so that a terminal may be connected with a standard cable When a data byte is received by the UART the RxRDY output interrupts the CPU to prevent the data from being overwritten GPIB Interface The interface to the GPIB is provided by U802 an MC68488 General Purpose Interface Adapter GPIA The GPIB data and control lines are buffered by drivers U808 and U811 Because the GPIA uses a 1 MHz clock wait states are provided by U805 to synchronize I O transactions with the
80. e voltage that you would see across this 1MQ resistor we multiply 0 1340 V NHz by the square root of the detector bandwidth If for example we were looking at all frequencies between dc and 1 MHz we would expect to see an rms Johnson noise of V2 1 2 0 13 uV AHz 108 Hz 1 2 130 uV 1 f Noise Arising from resistance fluctuations in a current carrying resistor the mean squared noise voltage due to 1 f noise is given by V2 A R212 Af f where A is a dimensionless constant 10 11 for carbon R is the resistance the current Af the bandwidth of our detector and f is the frequency to which the detector is tuned For a carbon resistor carrying 10 mA with R 1k Af f 1Hz we have 36 And Others Other noise sources include flicker noise found in vacuum tubes and generation and recombination noise found in semiconductors All of these noise sources are incoherent Thus the total noise is the square root of the sum of the squares of all the incoherent noise sources Non Essential Noise Sources In addition to the intrinsic noise sources listed above there are a variety of non essential noise sources i e those noise sources which can be minimized with good laboratory practice It is worthwhile to look at what might be a typical noise spectrum encountered in the laboratory environment Power Lina and Harmonics Broadcast Stations T Fh Broadcasts Noise RADAR 14 Backy ou
81. ecification Value Error Full Scale Sensitivity 100 nV Dynamic Reserve 60 dB Reference Frequency 5 kHz Gain Accuracy 196 196 Output Stability 01 1 Front End Noise lt 7 nV Hz 1 296 Output Time Constant 10 S 0 796 Total RMS Error 296 Shielding and Ground Loops In order to achieve the 296 accuracy given in this measurement example we will have to be careful to minimize the various noise sources which can be found in the laboratory See Appendix A for a brief discussion on noise sources and shielding While intrinsic noise Johnson noise 1 f noise and alike is not a problem in this measurement other noise sources could be a problem These noise sources can be reduced by proper shielding There are two methods for connecting the lock in to the experiment the first method is more convenient but the second eliminates spurious pick up more effectively In the first method the lock in uses the A input in a quasi differential mode Here the lock in detects the signal as the voltage between the center and outer conductors of the A input The lock in does not force A s shield to ground rather it is connected to the lock in s ground via a 101 resistor Because the lock in must sense the shield voltage in order to avoid the large ground loop noise between the experiment and the lock in any noise pickup on the shield will appear as noise to the lock in For a low impedance source as is the case here the noise picke
82. ed to a setting for which the dynamic reserve is not allowed the dynamic reserve will change to the next setting which is allowed Sensitivity takes precedence over the dynamic reserve The sensitivity range of each dynamic reserve is shown below Dynamic Reserve Sensitivity Range LOW 1 uV through 500 mV NORM 100 nV through 50 mV HIGH 100 nV through 5 mV Dynamic Reserve The dynamic reserve DR is set using the keys in the DYNAMIC RESERVE section The reserve is displayed by the three indicator LED s HIGH NORM LOW Only those dynamic reserve settings available for the sensitivity are allowed see above table For example when the sensitivity is 500 mV the DR will always be LOW The dynamic reserve and output stability of each setting are shown below Setting Dynamic Reserve Output Stability ppm C LOW 20 dB 5 NORM 40 dB 50 HIGH 60 dB 500 Since a higher DR results in degraded output stability you should use the lowest DR setting for which there is no overload indication Note that using the Bandpass Filter provides about 20dB of additional DR and so allows you to operate with a lower DR setting Status There are five STATUS LED s OVLD indicates a signal overload This condition can occur when the signal is too large the sensitivity is too high the dynamic reserve is too low the offset is on the expand is on the time constant is not large enough or the ENBW is too large UNLK indicates that
83. ence The reference frequency is measured to 1 part in 256 resolution Phase Controls The phase shift between the reference oscillator and the reference input is set using the four keys in the PHASE section The two keys below the FINE label increment the phase setting in small amounts A single key press will change the phase by 0 025 degrees in the desired direction Holding the key down will continue to change the phase with larger and larger steps with the largest step being 10 degrees The two 90 keys are used to change the phase by 90 degree increments The upper key will add 90 degrees and the lower key will subtract 90 degrees Holding both keys down at once sets the phase shift back to zero The REFERENCE DIGITAL DISPLAY automatically displays the phase whenever any of the PHASE keys are pressed The phase ranges from 180 degrees to 180 degrees and is the phase delay from the reference input signal Power This is the instrument s POWER switch When the power is turned off the front panel settings are retained so that the instrument will return to the same settings when the power is next turned on When the power is turned on the OUTPUT DIGITAL DISPLAY will show the SERIAL NUMBER of the instrument and REFERENCE DISPLAY shows the model number of the instrument All displays return to normal after 2 seconds Local and Remote When the instrument is programmed via the computer interface to be in the REMOTE state WIT
84. ent combining state of the art analog design with advanced microprocessor based control and interfaces This discussion is intended to aid the advanced user in gaining a better understanding of the instrument The SR510 has 8 main circuit areas the signal amplifier the reference oscillator the demod ulator the analog output and controls the front panel the microprocessor the computer inter faces and the power supplies With the exception of the front panel and a few pieces of hardware the entire lock in is built on a single printed circuit board Each section is isolated from the others as much as possible to prevent spurious signal pickup To aid in the location of individual components the first digit of each part number generally refers to the schematic sheet number on which it occurs To help find the part on the circuit board the parts list includes a location on the circuit board for each component Signal Amplifier Assuming the input selector switch is set to a voltage input the signal is coupled in through capacitors C101 and C102 The input impedance is set by the 100 MO resistors R101 and R102 over the operating frequency range Note that R103 isolates the signal shields from the instrument ground forcing the return signal current back along the cable shields The signal is then applied differentially to the gates of Q101 Q101 is a low noise dual JFET The drain current through R109 is kept constant by 2 2 0101 Th
85. er Note that if the auto Offset is on an O 1 command will turn the auto Offset off and turn the manual offset on without changing the actual offset value v If v is absent the P command returns the phase setting from 180 to 180 degrees When v is included the phase is set to the value of v up to 999 degrees Q The Q command returns the output reading in units of volts For an input signal of 50 uV on a full scale sensitivity of 100 uV the Q command will return the string 50 00E 6 The parameter read is the same as that being shown on the output display and can be changed with the S command R If n is included the command sets the reference input trigger mode If n is absent the trigger mode is returned n Mode 0 Positive 1 Symmetric 2 Negative S n If n is included the S command selects the parameter shown on the analog meter and output digital display as well as the output BNC If n is absent the parameter being displayed is returned n Display 0 X 1 Offset 2 Noise T m n The T command sets and reads the status of the time constants If m is 1 the pre time constant is selected if m is 2 the post time constant is selected The parameter m is required If n is included the T command sets the selected time constant If n is absent the setting of the selected time constant is returned Pre Time Constant m 1 1 mS 3 mS 10 mS 30 mS 100 mS 300 mS 1 S 3 S 10 S 30 S 10
86. erminal General Power Mechanical Warranty SR510 Specification Summary 100 120 220 240 VAC 50 60 Hz 35 Watts Max 17 x 17 x 3 5 Rack Mount Included 12 Ibs Two years parts and labor Signal Channel Inputs Impedance Full Scale Sensitivity Maximum Inputs Noise Common Mode Gain Accuracy Gain Stability Signal Filters Dynamic Reserve Voltage Single ended or True Differential Current 10 Volts Amp Voltage 100 MQ 25 pF ac coupled Current 1 to virtual ground Voltage 100 nV 10 nV on expand to 500 mV Current 100 fA to 0 5 pA Voltage 100 VDC 10 VAC damage threshold 2 VAC peak to peak saturation Current 10 A damage threshold 1 pA ac peak to peak saturation Voltage 7 nV NHz at 1 kHz Current 0 13 pA VHz at 1 kHz Range 1 Volt peak Rejection 100 dB dc to 1KHz Above 1KHz the CMRR degrades by 6 dB Octave 196 2 Hz to 100KHz 200 ppm C 60 Hz notch 50 dB Q 10 adjustable from 45 to 65 Hz 120 Hz notch 50 dB Q 10 adjustable from 100 to 130 Hz Tracking bandpass set to within 1 of ref freq Q 5 20dB LOW 1 uV to 500 mV sensitivity 40dB NORM 100 nV to 50 mV sensitivity 60dB HIGH 100 nV to 5 mV sensitivity Bandpass filter adds 20 dB to dynamic reserve Line Notch filters increase dynamic reserve to 100 dB Reference Channel Frequency Input Impedance Trigger Mode 0 5 Hz to 100 kHz 1 MO ac coupled SINE 100 mV minimum 1Vrms nominal PULSE 1 Volt 1 usec m
87. erminated with transmits str to COMI rxstr str str must be declared with length of 15 or greater fills str with string received from COMI if and error occurs nocom is called Nocom should be a FORTRAN subroutine in your program program test character 20 strl str2 Example program to read the SR510 outputs and ramp the X6 analog output using Microsoft FORTRAN v3 3 and the COM1 port Set all switches SW2 to UP on SR510 for 19 2 kbaud initialize 1 port to 19 2 kbaud call init set character wait interval to zero call 05 reset X6 to zero 6 0 0 read output into string variable strl call txstr q call rxstr strl convert string variable into real variable vl read str1 1000 vl format bn f10 0 43 2000 3000 print results to screen write 2000 vl format Output 1 G10 3 ramp x6 by 2 5 mV x6 x6 0025 if x6 gt 10 x6 0 0 make x6 command string write str2 3000 x6 format x6 f7 3 call txstr str2 and loop forever goto 20 stop end ACKCkCk kkk k k k k k k k k k k k k k k k k k k k k k k kk kx KKK subroutine nocom in case of a timeout error this routine runs put your error handler here write char 7 write RS232 Tiemout Error stop end 44 Program Example 3 PC Microsoft C v3 0 via RS232 Machine language routines to interface to the COM 1 RS232 port are provided in the file RS232 O
88. gnal generator as the reference input if it is available Connect the sine output of the signal generator to the A input and set the input selector to A With the SENSITIVITY at 100mV adjust the amplitude of the input signal to 100mV full scale Now set the input selector to A B and connect the signal to both the A and B inputs Set the SENSITIVITY to 20uV the DYN RES to NORM and the BANDPASS fiter IN Connect the scope to the SIGNAL MONITOR output on the rear panel Set the scope to AC coupled 0 2V div and 10mS div Externally trigger the scope using the reference input signal The CMRR is adjusted by the single turn potentionmeter located at A1 under the single hole at the front of the signal shield The shield is the aluminum box on the left side of the main board Using a small screwdriver carefully adjust the pot to minimize the 100 Hz output on the scope After nulling the output set the sensitivity to 20V and null the output again Notch Filters Set the reference frequency to 60 0 Hz 50 0 Hz It is convenient to use the SYNC output of the signal generator as the reference input if it is available Connect the sine output of the signal generator to the A input and set the input selector to A With the SENSITIVITY at 100mV adjust the amplitude of the input signal to 100 mV full scale Set the LINE NOTCH to IN the SENSITIVITY to 10 and the DYN RES to LOW Connect the scope to the SIGNAL MONITOR output on the
89. hifted and shaped to provide a precision sine wave to the phase sensitive detector Phase Sensitive Detector The Phase Sensitive Detector is a linear multiplier which mixes the amplified and filtered signal with the reference sine wave The difference frequency component of the multiplier s output is a dc signal that is proportional to the amplitude of the signal The low pass filter which follows can reject any frequency components which are more than a fraction of a Hertz away from the signal frequency DC Amplifier and System Gain A dc amplifier amplifies the output of the low pass fillers The total system gain is the product of the ac and dc amplifier gains The partitioning of the System gain between these two amplifiers will affect the stability and dynamic reserve of the 29 instrument The output is most stable when most of the gain is in the ac amplifier however high ac gain reduces the dynamic reserve For the most demanding applications the user may specify how the system gain is partitioned However with prefilters that are able to provide up to 100 dB of dynamic reserve and with chopper stabilized dc amplifiers most users will not be concerned with just how the system gain is allocated A Microprocessor Based Design The instrument was designed to take full advantage of its microprocessor controller This approach provides several key advantages The instrument may be interfaced to a laboratory computer
90. ilm 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Capacitor Ceramic Disc 50V 10 SL Capacitor Polystyrene 50V 5 Ax Cap Polyester Film 50V 5 40 85c Rad Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c Cap Stacked Metal Film 50V 5 40 85c SR510 PARTS LIST REF SRS part VALUE 50 C214 5 00059 512 470 51 C215 5 00060 512 1 0U 52 C216 5 00056 512 1U 53 C217 5 00038 509 10U 54 C218 5 00038 509 10U 55 C230 5 00055 512 15U 56 C301 5 00060 512 1 0U 57 C302 5 00003 501 10 58 C303 5 00009 501 24 59 C304 5 00110 525 560 60 C305 5 00038 509 10U 61 C306 5 00060 512 1 0U 62 C307 5 00049 566 0010 63 C308 5 00058 512 33U 64 C310 5 00008 501 22P 65 C311 5 00008 501 22P 66 C312 5 00017 501 47 67 C313 5 00017 501 47 68 C314 5 00056 512 1U 69 C315 5 00038 509 10U 70 C317 5 00060 512 1 0U 71 C318 5 00049 566 0010 72 C319 5 00058 512 33U 73 C320 5 00049 566 0010 74 321 5 00003 501 10 75 C322 5 00003 501 10 76 C323 5 00035 521 47U 77 C324 5 00035 521 470 78 C325 5 00100 517 2 2U 79 C326 5 00100 517 2 20 80 C327 5 00100 517 2 20 81 C328 5 00100 517 2 20 82 C329 5 00033 520 47U 83 C330 5 00100 517 2 20 84 C331 5 00100 517 2 20 85 C332 5 00100 517 2 20 86 C333 5 00100 517 2 20 87 C334 5 00100 517 2 20 88 C335 5 00016 501 470P 89 C336 5 00016 501 470P 90 C337 5 00100 517 2 2U 91 C338 5 00100 517 2 2
91. ing resistors A voltage proportional to the reference frequency is converted into a current by 1 4 0208 0201 This current programs the effective resistance of the two transconductance amplifiers and thus tunes the center frequency of the filter to follow the reference The output of the filter is buffered by 4 4 U201 The two remaining op amps in U208 are used to detect signal overloads throughout the amplifier chain Reference Oscillator The reference input signal is ac coupled and buffered by 0301 R378 isolates the reference shield from the lock in ground to prevent ground loop currents 1 2 U303 switches the polarity of the reference reaching comparator U304 U305 is a retriggerable one shot whose output indicates a no reference condition if no comparator pulses are generated for 3 seconds U309 is a dual transconductance amplifier in a triangle VCO configuration U310 selects the integrating capacitor depending on the frequency range The VCO frequency is determined by the programming current through R318 and therefore by the output voltage of U308 C306 is the phase locked loop low pass filter which is buffered by 0308 0307 is a programmable current source used to charge and discharge C306 The amount of current available to U307 is determined by the VCO control voltage thus the tracking rate of the VCO is proportional to the VCO frequency The triangle output is compared to a constant voltage by U314 1 2 0313 and
92. inimum width Fundamental f or 2nd Harmonic 2f Acquisition Time Slew Rate Phase Control Phase Noise Phase Drift Phase Error Demodulator Stability Time Constants Offset Harmonic Rej 25 Sec at 1 Hz 6 Sec at 10 Hz 2 Sec at 10 kHz 1 decade per 10 S at 1 kHz 90 shifts Fine shifts in 0 025 steps 0 01 rms at 1 kHz 100 msec 12 dB TC 0 1 G Less than 1 above 10Hz 5 on LOW dynamic reserve 50 ppm C on NORM dynamic reserve 500 ppm C on HIGH dynamic reserve Pre 1msec to 100 sec 6 dB Octave Post 1sec 0 1 sec none 6 dB Octave or none Up to 1X full scale 10X on expand 55 dB bandpass filter in Outputs amp Interfaces Outputs Output Meter Output LCD Output BNC Reference LCD RS232 GPIB A D D A Ratio Internal Oscillator X 50 X Offset Noise 2 Precision mirrored analog meter Four digit auto ranging LCD display shows same values as the analog meters 10 V output corresponds to full scale input lt 1Q output impedance Four digit LCD display for reference phase shift or frequency Interface controls all functions Baud rates from 300 to 19 2 K Interface controls all functions IEEE 488 Std 4 BNC inputs with 13 bit resolution 10 24 V 2 BNC outputs with 13 bit resolution 410 24 V Ratio output equals 10X output divided by the Denominator input Range 1 Hz to 100 kHz 1 accuracy Stability 150 ppm C Distortion 2 THD Amplitude 196 accura
93. is always equal to 1 5th of the center frequency The center frequency is continually adjusted to be equal to the internal demodulator frequency When the reference mode is f the filter tracks the reference When the mode is 2f the filter frequency is twice the reference input frequency The center frequency tracks as fast as the reference oscillator can slew and may be used during frequency scans The bandpass filter adds up to 20 dB of dynamic reserve for noise signals outside the pass band and increases the harmonic rejection by at least 13dB 2nd harmonic attenuated by 13 dB higher harmonics attenuated 6dB octave more If not needed to improve the dynamic reserve or the harmonic rejection then the filter should be left OUT Sensitivity The sensitivity is displayed as a value 1 500 and a scale nV uV mV When using the current input which has a gain of 106 V A these scales read fA pA and nA The two keys in the SENSITIVITY section move the sensitivity up and down If either key is held down the sensitivity will continue to change in the desired direction four times a second The full scale sensitivity can range from 100 nV to 500 mV The sensitivity indication is not changed by the EXPAND function The EXPAND function increases the output sensitivity Volts out volts in as well as the resolution of the digital output display Not all dynamic reserves are available at all sensitivities If the sensitivity is chang
94. ithout a computer become simple when a computer is used to coordinate various parts of the experiment The Internal Oscillator provides a reference source for the lock in This allows the lock in s frequency to be set without an additional signal generator It also provides a sine wave to be used as the signal stimulus in an experiment The frequency may be set via the computer interface as well as manually LOCK IN AMPLIFIER DIAGRAM LOW NOISE LINE FREQUENCY ZxLINE FREQUENCY DIFFERENTIAL AMPLIFIER NOTCH FILTER NOTCH FILTER DIFFERENTIAL VOLTAGE INPUTS CURRENT INPUT 5 CURRENT VOLTAGE CONVERTER REFERENCE INPUT c INPUT DISCRIMINATOR PHASE LOCK LOOP PRECISON SINE CONVERTER LINEAR PHASE SENSITIVE DETECTOR QUADRATURE PHASELOCK REAR PANEL A D INPUTS 100 AND RATIO INPUT ANALOG MULTIPLEXER AND S H AMPLIFIER PRECISION SINE CONVERTER DIGITAL CONTROLS AC AND D C GAINS FILTERS BANDPASS FILTER LOW PASS FILTERS INPUT DISCRIMINATOR RANCE PHASE SHIFT CONTROL 1 2 SELECTION u PROCESSOR SYSTEM RS 232 IEEE 488 COMPUTER INTERFACE SR510 Block Diagram Several new concepts are used to simplify the design of SR510 lock in amplifier In addition to implementing recent advances in linear integrated circuit technology the instrument was designed to take full advantage of its microprocessor controller to improve performance and to reduce cost As
95. itive to harmonics This approach has eliminated the difficulty performance compromises and cost of the older techniques The Signal Channel The instrument has both current and voltage inputs The current input is a virtual ground and the 100 MQ voltage inputs can be used as single ended or true differential inputs There are three signal filters Each of these filters may be switched in or out by the user The first filter is a line notch filter Set to either 50 or 60 Hz this filter provides 50 dB of rejection at the line frequency The second filter provides 50 dB of rejection at the first harmonic of the line frequency The third filter is an auto tracking bandpass filter with a center frequency tuned by the micro processor to the frequency of the signal These three filters eliminate most of the noise from the signal input before the signal is amplified A high gain ac amplifier is used to amplify the signal before entering the phase sensitive detector The high gain which is available from this programmable amplifier allows the lock in to operate with a lower gain in its dc amplifier This arrangement allows high stability operation even when used on the most sensitive ranges Reference Channel The processor controlled reference input discriminator can lock the instrument s PLL to a variety of reference signals The PLL can lock to sine waves or to logic pulses with virtually no phase error The PLL output is phase s
96. kHz So as to be in a relatively quiet part of the noise spectrum This frequency is high enough to avoid low frequency 1 f noise as well as line noise The frequency is low enough to avoid phase shifts and amplitude errors due to the RC time constant of the source impedance and the cable capacitance The full scale sensitivity of 100 nV matches the expected signal from our sample The sensitivity is calibrated to 196 The instrument s output stability also affects the measurement accuracy For the required dynamic reserve the output stability is 0 1 C For a 10 C temperature change we can expect a 1 error A front end noise of 7 nV VHz will manifest itself as a 1 2 nVrms noise after a 10 second low pass filler since the equivalent noise bandwidth of a 25 single pole filter is 1 4RC The output will converge exponentially to the final value with a 10 second time constant If we wait 50 seconds the output will have come to within 0 7 of its final value The dynamic reserve of 60 dB is required by our expectation that the noise will be a thousand times larger than the signal Additional dynamic reserve is available by using the bandpass and notch filters A phase shift error of the PLL tracking circuits will cause a measurement error equal to the cosine of the phase shift error The SR510 s 1 phase accuracy will not make a significant contribution to the measurement error Specifications for the Example Measurement Sp
97. le using the RS232 non echo mode would be 5 lt cr gt 4 lt cr gt 45 10 lt cr gt Front Panel Status LED s The ACT LED flashes whenever the SR510 is sending or receiving characters over the computer interfaces The ERR LED flashes whenever an error has occurred such as an illegal command has been received a parameter is out of range or a communication buffer has exceeded 240 characters This LED flashes for about three seconds on power up if the battery voltage is insufficient to retain previous instrument settings The REM LED is on whenever the SR510 is programmed to be in the remote state RS232 Echo and No Echo Operation In order to allow the SR510 to be operated from a terminal an echo feature has been included which causes the unit to echo back commands received over the RS232 port This feature is enabled by setting switch 6 on SW2 to the DOWN position In this mode the SR510 will send line feeds in addition to carriage returns with each value returned and will also send the prompts OK gt and gt to indicate that the previous command line was either processed or contained an error Operating the SR510 from a terminal is an ideal way to learn the commands and responses before attempting to program a computer to control the SR510 When the unit is controlled by a computer the echo feature should be turned off to prevent the sending of spurious characters which the computer is not expecting Try Out with an ASCI
98. led X5 and X6 The voltages at these ports may be programmed via the computer interfaces The range is 10 24 V to 10 24 V and the resolution is 2 5 mV The output impedance is lt 10 and the output current is limited to 20 mA Ratio Output X5 is the ratio output when not programmed by the computer interface or set via the front panel X5 becomes the ratio output whenever the unit is turned on The voltage at X5 is the ratio of the detected signal output X to the analog voltage at port X1 An output of 10 V corresponds to a ratio of 1 The ratio is computed by digitizing the demodulator output and the voltage at port X1 and then taking the ratio The resolution is 0 0025 V For best accuracy the sensitivity should be set to provide at least a 50 full scale signal and the analog denominator X1 should be 5V or greater The ratio is updated approximately every 1 5 mS For the Ratio feature to work the voltage at the denominator input must exceed 40 mV Internal Oscillator The INTERNAL OSCILLATOR is a voltage controlled oscillator with a sine wave output To use the oscillator as the reference source connect the REF OUTPUT on the rear panel to the REF INPUT on the front panel The REF OUTPUT is a 1 Vrms sine wave The SINE OUTPUT may be used as the stimulus to the experiment The SINE OUTPUT can be set to three amplitudes 1 V 100 mV and 10 mV rms using the amplitude switch The output impedance is 6000 The CAL sc
99. ment x6 output by 2 5 mV if x gt 10 x 0 sprintf str2 X6 f x make command string txstr str2 send x6 command print results to screen printf Output 10 36 n v1 kk x x k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k k kx x x x nocom error handling routine goes here printf RS232 Timeout Error n putch 7 exit 46 Program Example 4 PC Microsoft Basic via GPIB This program requires the Capital Equipment Corporation GPIB card for the IBM PC or XT It has firmware in ROM to interface high level languages to the GPIB Subroutine calls in Microsoft BASIC are done to memory locations specified by the name of the subroutine The address is relative to the segment address specified by the DEF SEG statement preceding CALL In this program the CEC card s ROM starts at the system controller s address is 21 and the SR530 has been assigned as GPIB address 23 To monitor the GPIB activity with an RS232 terminal SW1 6 should be down and the ASCII terminal should be attached to the rear panel RS232 connector 10 EXAMPLE PROGRAM TO READ T
100. mmetry at low frequencies 4 4 U1 buffers the output of U2 P1 adjusts the amplitude of the output sine wave The output amplitude on the SIne Out is selected by the amplitude switch The output impedance is 6000 Calibration and Repair This section details calibration of the instrument Calibration should only be done by a qualified electronics technician k k k k k k k kkk WARNING k k k Kk Kk k k k kk The calibration procedure requires adjusting the instrument with power applied and so there is a risk of personal injury or death by electric shock Please be careful Most of the calibration parameters are determined by a computer aided calibration procedure after burn in at the factory These calibration parameters are quite stable and so will not need to be adjusted Calibration parameters which may need field adjustment are detailed below Multiplier Adjustments On the HIGH dynamic reserve setting there can be some reference frequency feedthrough This section describes how to null this unwanted output This adjustment requires an oscilloscope and a signal generator which can proved a 500Hz reference signal Allow the unit to warm up for about 1 hour Reset the unit by turning it off and back on while holding the REL key down Select voltage input and connect a 500 terminator or shorting plug to the A input BNC connector Connect the 500 Hz reference signal to the reference input Set the SENSITVITY to 1mV an
101. nce the characters from different sources can become interleaved on the command queue and result in unrecognized command errors The Lock in Technique The Lock in technique is used to detect and measure very small ac signals A Lock in amplifier can make accurate measurements of small signals even when the signals are obscured by noise sources which may be a thousand times larger Essentially a lock in is a filter with an arbitrarily narrow bandwidth which is tuned to the frequency of the signal Such a filter will reject most unwanted noise to allow the signal to be measured A typical lock in application may require a center frequency of 10 KHz and a bandwidth of 0 01 Hz This has a Q of 106 well beyond the capabilities of passive electronic filters In addition to filtering a lock in also provides gain For example a 10 nanovolt signal can be amplified to produce a 10 V output a gain of one billion All lock in measurements share a few basic principles The technique requires that the experiment be excited at a fixed frequency in a relatively quiet part of the noise spectrum The lock in then detects the response from the experiment in a very narrow bandwidth at the excitation frequency Applications include low level light detection Hall probe and strain gauge measurement micro ohm meters C V testing in semiconductor research electron spin and nuclear magnetic resonance studies as well as a host of other sit
102. nd G cr The response should be 24 meaning that the sensitivity is at the 24th setting or 500 mV Change the sensitivity by typing G19 cr The sensitivity should now be 10 mV Check the front panel to make sure this is so The output of the lock in is read by typing the command Q1 cr The response is a signed floating point number with up to 5 significant digits plus a signed exponent Change the gain to 10 uV using the G10 command The response to the Q1 command will now be similar to the previous one except that the exponent is different Attach a DC voltmeter to the X6 output on the rear panel The range should allow for 10V readings The voltage at the X6 output can be set using the X6 command Type 6 5 0 lt gt and the X6 output will change to 5 0V To read this back to the terminal just type X6 lt cr gt When setting the X6 voltage the voltage may be sent as an integer 5 real 5 000 or floating point 0 500E1 number Now connect the X6 output to the X1 input also on the rear panel X1 through X4 are analog input ports To read the voltage on X1 simply type X1 lt cr gt The response 5 000 should appear on the terminal The analog ports X1 through X6 can be used by your computer to read outputs of other instruments as well as to control other laboratory parameters At this point the user should experiment with a few of the commands A detailed command list follows SR510 Command List The first lette
103. nd then lift them out 4 The input transistors are located on the main board just behind the input selector switch Q101 is the voltage A A B front end and Q102 is the current 1 front end Desolder and replace the appropriate transistor 5 Replace the signal shields Be careful to check that the shields do not touch any circuit board traces around their edges 6 Replace the top and bottom panels 7 If Q101 the voltage front end has just been replaced the Common Mode Rejection needs to be readjusted using the procedure described in the Amplifier Adjustments section Appendix A Noise Sources and Cures Noise random and uncorrelated fluctuations of electronic signals finds its way into experiments in a variety of ways Good laboratory practice can reduce noise sources to a manageable level and the lock in technique can be used to recover signals which may still be buried in noise Intrinsic Noise Sources Johnson Noise Arising from fluctuations of electron density in a resistor at finite temperature these fluctuations give rise to a mean square noise voltage V2 4kT Re Z f df 4kTR Af where k Boltzman s constant 1 38x10 23J K is the absolute temperature in Kelvin the real part of the impedance Re z f is the resistance R and we are looking at the noise source with a detector or ac voltmeter with a bandwidth of Af in Hz For a 1MQ resistor 2 1 2 0 13 V Hz To obtain the rms nois
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105. o operate correctly the SR510 and the terminal must have the same settings for baud rate parity and number of stop bits The control lines in the RS232 Standard which are used to indicate that a device is ready to accept data must also be connected correctly at the terminal end If 39 the terminal responds to a control line it will believe that the SR510 is not ready to accept data because the line is not passed in this example and will therefore not send any data CASE 2 RS232 with Control Lines DEVICE A DEVICE B The data lines are the same as in Case 1 In addition to the data lines there are two control lines used CTS Pin 5 Clear to send is a signal asserted by the DCE to tell the DTE that the DCE is ready to receive data DTR Pin 20 Data Terminal Ready is a signal asserted by the DTE to tell the DCE that the DTE is ready to receive data The SR510 responds to the control lines as follows 1 Ifthe lines are not connected the SR510 assumes that you are ready to receive data 2 Data will not be transmitted from the SR510 if the DTR line pin 20 is low This is useful in the case when your program is not yet ready to receive data If data transmission is not suspended then data may be overwritten in your computer s UART as it is not being retrieved by the program and so will be lost When this happens the over run flag will be set in your computer s UART and it may be recognized b
106. on will take longer to settle To obtain a value for the noise density the noise reading should be divided by the square root of the ENBW Thus when the ENBW is 1 Hz the noise output is the noise density and when the ENBW is 10 Hz the noise density is the noise output divided by 410 For example if the input noise is measured to be 7 nV with the ENBW set to 1 Hz the noise density is 7 nV VHz Switching the ENBW to 10 Hz results in a faster measurement and a reading of 22 nV on the output The noise density is 22 nV 410 Hz or 7 nV VHz Atfrequencies gt 10 Hz the noise density should be independent of the ENBW Reference and Trigger Level The REFERENCE INPUT BNC is located in this section The input is ac coupled and the impedance is 1 MO The dc voltage at this input should not exceed 100 V and the largest ac signal should be less than 10 V peak The three indicators above the input BNC display the TRIGGER MODE The single key above the input BNC is used to select the TRIGGER MODE If the center TRIGGER MODE LED is on the mode is SYMMETRIC and the reference oscillator will lock to the positive zero crossings of the ac reference input The ac signal must be symmetric e g sine wave square wave etc have peak to peak amplitude greater than 100 mV A signal with 1 Vrms amplitude is recommended The phase accuracy of the reference channel is specified for a 1Vrms sinewave in the symmetric trigger mode If the up
107. ormal 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 and 120V use a 1 Amp fuse and for 220V and 240V use a 1 2 Amp fuse LINE CORD This instrument has a detachable three wire power cord with a three contact plug for connection to both the power source and protective ground The protective ground contact connects to the accessible metal parts of the instrument To prevent electrical shock always use a power source outlet that has a properly grounded protective ground contact OPERATE WITH COVERS IN PLACE To avoid personal injury do not remove the product covers or panels Do not operate the product without all covers and panels in place WARNING REGARDING USE WITH PHOTOMULTIPLIERS It is relatively easy to damage the signal inputs if a photomultiplier is used improperly with the lock in amplifier When left completely unterminated a PMT will charge a cable to a few hundred volts in a very short time If this cable is connected to the lockin the stored charge may damage the front end transistors To avoid this problem provide a leakage path of about 100 KO to ground inside the base of the PMT to prevent charge accumulation Symbols you may find on SRS products Alternating current Caution risk of electric shock Frame or chassis terminal Caution refer to accompanying documents Earth ground t
108. otch is selected The parameter m is required If n is 1 the L command sets the selected filter in If n is 0 the selected filter is taken out If n is absent the status of the selected filter is returned M n If nis 1 the M command sets the reference mode to 2f If n is 0 the reference mode is set tof If n is absent the reference mode is returned N m If m is 1 the N command sets the ENBW to 10 Hz If m is 0 the ENBW is set to 1 Hz If m is absent the ENBW setting is returned v If nis 1 the command turns the offset If n is 0 the offset is turned off If n is absent the offset status on or off is returned The value of the offset is read using the S and Q commands If n is included then v may also be sent v is the offset value up to plus or minus full scale in units of volts For example to offset half of full scale on the 100 uV sensitivity v should be 50 0E 6 or an equivalent value However if the sensitivity is then changed to 200 uV the offset is now half of the new full scale or 100 uV When the sensitivity is changed the offset is retained as a constant fraction of full scale rather than as a voltage referred to the input The expand function will on the other hand preserve the value of the offset as an input referred voltage Once a value of v is sent the offset may be turned off and on without losing the offset value by using the O command without the v paramet
109. p bits of the terminal must match those of the SR510 and the computer If your terminal has a mode which will display control characters such as carriage returns and line feeds it is helpful to operate in that mode A variant of the eavesdropping approach is diagrammed below With this cable arrangement the ASCII terminal can listen to the data passing in both directions The only drawback is that the terminal will display garbled data if both devices transmit data at the same time Appendix C Introduction to the GPIB The IEEE 488 Standard specifies the voltage levels handshake requirements timing hardware details pinout and connector dimensions for a 16 line bit parallel bus Many instruments may be connected in series to communicate over the same cable Because the bits are passed in parallel the GPIB is faster than the RS232 The controller generally your computer coordinates data transfer on the bus by designating all participating instruments including itself as either a talker or a listener Listeners can receive data placed on the bus by the Talker Devices can have the capacity to operate in either mode The address of each device is set by switches in the device and must be between 0 and 30 Bus Description Byte Transfer Control Group This consists of 3 negative logic lines that implement the GPIB handshaking The NRFD Not Ready For Data line is held low by any designated listener who is not ready
110. per TRIGGER MODE LED is on the mode is POSITIVE The trigger threshold is 1V and the reference oscillator will lock to the positive going transitions of the reference input This mode triggers on the rising edges of a TTL type pulse train The pulse width must be greater than 1 uS If the lower TRIGGER MODE LED is on the mode is NEGATIVE The trigger threshold is 1V and the reference oscillator will lock to the negative going transitions of the reference input This mode triggers on a negative pulse train or on the falling edges of a TTL type pulse train remembering that the input is ac coupled The pulse width must be greater than 1 uS Above the TRIGGER MODE indicators are the REFERENCE MODE LED s The key below the REFERENCE MODE indicators toggles between f and 2f When the MODE is f the lock in will detect signals at the reference input frequency When the MODE is 2f the lock in detects signals at twice the reference input frequency In either case the reference oscillator has a maximum frequency of 100 KHz thus when in the 2f mode the reference input frequency may not exceed 50 KHz The REFERENCE DIGITAL DISPLAY shows either the reference oscillator frequency or phaseshift The displayed parameter toggles between the two whenever the SELECT key is pressed The appropriate scale indicator below the display will be on It is useful to check the frequency display to verify that the lock in has correctly locked to your refer
111. ports There are also two programmable analog output ports available to provide general purpose control voltages Communicating with the SR510 Before using either the RS232 or GPIB interface the appropriate configuration switches need to be set There are two banks of 8 switches SW1 and SW2 located on the rear panel SW1 sets the GPIB address and SW2 sets the RS232 parameters The configuration switches are read continuously and any changes will be effective immediately For details on switch settings see page 7 at the front of this manual Command Syntax Communications with the SR510 use ASCII characters Commands to the SR510 may be in either UPPER or lower case A command to the SR510 consists of one or two command letters arguments or parameters if necessary and an ASCII carriage return cr or line feed lt or both The different parts of the command do not need to be separated by spaces If spaces are included they will be ignored If more than one parameter is required by a command the parameters must be separated by a comma Examples of commands are G 5 lt cr gt setthe sensitivity to 200 nV 1 4 lt cr gt set the pre filter to 30 mS F cr read the reference frequency 45 10 cr set phase shift to 45 10 X 5 1 23E 1 cr set port X5 to 0 123 V Multiple commands may be sent on a single line The commands must be separated by a semicolon character The commands will not be exec
112. processed and all responses have been received Trouble Shooting Interface Problems If you are having difficulty getting your computer to communicate with the SR510 look to the sections on the RS232 and GPIB interfaces for some tips specific to your particular interface An ASCII terminal is a valuable aid for debugging interface problems You can use it to 1 2 become familiar with the SR510 s command structure see GPIB bus transactions by using the GPIB echo mode eavesdrop on transactions when using the RS232 interface substitute a human for the SR510 by using a null modem cable to make the DTE a DCE and attaching the terminal to the port to which you would normally have connected the SR510 This allows you to test your program s responses to inputs which you provide from the terminal Common Hardware Problems include 1 2 The RS232 or GPIB cables are not properly attached The configuration switches for the RS232 characteristics or GPIB address are not set correctly Make sure the RS232 echo is off when using the RS232 interface with a computer The GPIB with RS232 echo mode should be off when not debugging the GPIB interface Your computer requires an RS232 control line to be asserted but your cable does not pass it between the SR510 and the computer or your computer is not asserting the DTR line on the RS232 Common Software Problems include 1 You have sent the wrong command
113. r 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 SR510 PARTS LIST REF SRS part VALUE 509 R703 4 00027 401 1 5K 510 R705 4 00021 401 1 0K 511 R706 4 00034 401 10K 512 R707 4 00034 401 10K 513 R708 4 00069 401 300K 514 R709 4 00034 401 10K 515 R710 4 00032 401 100K 516 R711 4 00034 401 10K 517 R712 4 00032 401 100K 518 R801 4 00034 401 10K 519 R802 4 00034 401 10K 520 R803 4 00065 401 3 3K 521 R901 4 00107 402 10 522 R902 4 00107 402 10 523 R903 4 00060 401 240 524 R904 4 00024 401 1 2K 525 R905 4 00024 401 1 2K 526 R906 4 00060 401 240 527 R907 4 00107 402 10 528 R908 4 00107 402 10 529 R909 4 00053 401 200 530 R910 4 00063 401 3 0K 531 R911 4 00063 401 3 0K 532 R912 4 00053 401 200 533 R913 4 00107 402 10 534 R914 4 00107 402 10 535 RN401 4 00220 420 10 8 536 RN801 4 00225 425 100 9 537 RN802 4 00225 425 100 9 538 50702 1 00026 150 28 PIN 600 MIL 539 SW1 2 00014 207 SPSTX8 540 SW 2 00014 207 SPSTX8 541 SW601 2 00017 216 4PDT 542 SW602 2 00004 213 DPDT 543 T1 6 00007 610 SR5
114. r in each command sequencoe is the command The rest of the sequence consists of parameters Multiple parameters are separated by a comma Those parameters shown in are optional while those without are required Variables m and n represent integer parameters while v represents a real number Parameters m and n must be expressed in integer format while v may be in integer real or floating point format A n If nis 1 the A command causes the auto offset routine to run Every time an A 1 command is received the auto offset function is executed If n is 0 then the auto offset is turned off If n is absent then the auto offset status is returned Note that if the manual offset is on an A 1 command will turn off the manual offset before executing the auto offset function B If nis 1 the B command sets the bandpass filter in If n is 0 the bandpass filter is taken out If n is absent then the bandpass filter status is returned C n If nis 1 the C command sets the reference LCD display to show the phase setting If n is 0 the LCD will display the reference frequency If n is absent the parameter being displayed frequency or phase is returned Note that the P and F commands are used to read the actual values of the phase and frequency D n If n is included the D command sets the dynamic reserve If n is absent the dynamic reserve setting is returned n Dyn Res 0 LOW 1 NORM 2 HIGH
115. rated by the no reference unlock overload and auto over range conditions will also reset the corresponding bit in the SRQ mask byte This is to prevent a constant error condition such as no reference applied to the input from continually interrupting the controller When such an SRQ occurs the controller should change some parameter so as to solve the problem and then re enable the SRQ mask bit again using the V command 23 GPIB with RS232 Echo Mode It is sometimes useful when debugging a GPIB system to have some way of monitoring exactly what is going back and forth over the bus The SR510 has the capability to echo all characters sent and received over the GPIB to its RS232 port This mode of operation is enabled by setting switch 6 of SW1 to the DOWN position The baud rate stop bits and parity of the RS232 port are still set by SW2 Of course the RS232 port operates at much lower speeds than the GPIB and will slow down the GPIB data rate in this mode Use the WO command to allow the RS232 interface to run at full speed otherwise the GPIB transactions may take so long that the controller can hang During actual use this mode should be disabled The SR510 with BOTH Interfaces If both interfaces are connected commands may be received from either interface Responses are always sent to the source of the request except in GPIB echo mode It is unwise to send commands from the two interfaces at the same time si
116. rcuit 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 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 Relay Relay Relay Relay SR510 PARTS LIST REF SRS part VALUE 611 U415 3 00126 335 51A05 612 0416 3 00084 340 7650 613 0417 3 00126 335 51A05 614 0418 3 00076 340 09211 615 U419 3 00090 340 LF411 616 U 420 3 00064 340 CA3081 617 0421 3 00035 340 74074 618 0501 3 00087 340 LF347 619 U502 3 00058 340 7524 620 0503 3 00046 340 74 374 621 U504 3 00077 340 DG528 622 U505 3 00059 340 AD7542JN 623 U506 3 00058 340 7524 624 U507 3 00077 34
117. rear panel Set the scope to AC coupled 0 2V div 10mS div Trigger the scope externally using the reference input signal The LINE NOTCH frequency and depth are adjusted by the pair of 20 turn potentiometers located under the middle two holes in the signal shield row 4 on the circuit board Using a small screwdriver carefully adjust one pot until the line output on the scope is minimized Then adjust the other pot until the output is minimized lterate between the two pots until there is no further improvement Set the SENSITIVITY to 5mV 2 and 1mV repeating the adjustments at each sensitivity Repeat this procedure using a reference frequency of 120 0 Hz 100 0 Hz and the LINEX2 NOTCH filter The LINEX2 NOTCH is adjusted by the pair of 20 turn potentiometers located under the back two holes in the signal shield row 5 on the circuit board Replace the top panel 35 Replacing the Front End Transistors Both the voltage and current front end transistors Q101 and Q102 are 2N6485 IMF6485 dual JFETS These transistors are selected at the factory to meet the noise specifications This section outlines their replacement procedure in the event that they become damaged during use 1 Remove the AC power cord from the unit 2 Remove top and bottom panels 3 Release the signal shields by removing the four screws which hold it onto the circuit board Be careful not to lose the nuts Carefully slide the shields back a
118. rent grounding points which are not at exactly the same potential Some cures for ground loop problems include 1 grounding everything to the same physical point 2 using a heavier ground bus to reduce the potential drop along the ground bus 3 removing sources of large currents from ground wires used for small signals 38 Microphonics provides a path for mechanical noise to appear as electrical noise in a circuit or experiment Consider the simple circuit below H Lock In Amplifier Coaxial Cable The capacitance of a coaxial cable is a function of its geometry so mechanical vibrations will cause the cable capacitance to vary with time Since C QN we have C dV V dC dQ dt dt dt so mechanical vibrations will cause a dC dt which in turn gives rise to a current i which will affect the detector Ways to eliminate microphonic signals include 1 eliminate mechanical vibrations 2 tie down experimental cables so they will not sway to and fro 3 use a low noise cable that is designed to reduce microphonic effects Thermocouple Effect The emf created by dissimilar metal junctions can give rise to many microvolts of dc potential and can be a source of ac noise if the temperature of the junction is not held constant This effect is large on the scale of many low level measurements Appendix B Introduction to the RS232 The RS232 is a standard for bit serial asynchronous data communication Th
119. response time of the SR510 preventing overwriting 6 Answers are coming back from the SR510 too slowly due to the W6 default setting for the character interval time Use the W command to speed up the transmission from the SR510 This can cause problems for the GPIB interface if the echo mode is on switch 6 of SW21 The SR510 with the RS232 Interface RS232 is a popular serial interface standard for bit serial communication Despite the existence of the standard there are many permutations of control lines baud rates and data formats If you do not have a lot of experience interfacing RS232 equipment you should read Appendix B for a description of the RS232 and interfacing tips Data Communications Equipment DCE The SR510 is configured as DCE so that it may be connected directly to a terminal If the SR510 is to be interfaced with another DCE device a special cable sometimes referred to as a modem cable is required To use the RS232 interface you must set the switches in SW2 to match your computer s baud rate parity and number of stop bits Refer to Page 7 for details Wait Command The SR510 normally waits until the RS232 Clear to Send control line CTS is asserted before sending characters However some computers do not set and reset the CTS line possibly causing the SR510 to send data when the computer is not ready to read it The SR510 may be slowed down using the W command Sending Wn causes the
120. rew Black All Types Hardware Misc Wire 18 UL1015 Strip 3 8 x 3 8 No Tin Wire 18 UL1015 Strip 3 8 x 3 8 No Tin Screw Black All Types Connector BNC Connector Male Socket THRU HOLE Line Cord Fabricated Part Fabricated Part Fabricated Part Fabricated Part Product Labels Shrink Tubing Shrink Tubing Shrink Tubing DESCRIPTION Cap Monolythic Ceramic 50V 20 Z5U Cap Monolythic Ceramic 50V 20 Z5U Capacitor Tantalum 35V 20 Rad Cap Stacked Metal Film 50V 5 40 85c Capacitor Silver Mica 500V 5 DM15 Capacitor Tantalum 35V 20 Rad Capacitor Ceramic Disc 50V 10 SL Capacitor Electrolytic 35V 20 Rad Capacitor Tantalum 35V 20 Rad Capacitor Electrolytic 35V 20 Rad Capacitor Tantalum 35V 20 Rad Pot Multi Turn Side Adjust Trim Pot Single Turn In Line Leads Pot Multi Turn Side Adjust Printed Circuit Board Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor 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 SR510 PARTS LIST NO REF SRS part VALUE 30 R15 4 00022 4
121. rew adjusts the amplitude The oscillator frequency is controlled by the VCO INPUT voltage A voltage from OV to 10V will adjust the frequency according to the VCO RANGE selected Three ranges are available 1 Hz V 100 Hz V and 10 KHz V The input impedance is 10 The FREQUENCY CAL screw adjusts the frequency There are four ways to set the frequency 1 Connect X5 or X6 D A outputs to the VCO INPUT The frequency is now controllable via the computer interfaces by programming X5 or X6 14 2 If the VCO INPUT is left open then the oscillator will run at the top of its range i e 10 Hz 1 KHz or 100 KHz 3 A 10 KO potentiometer may be connected from the VCO INPUT to ground This pot will then set the frequency 4 Connect the VCO INPUT to an external voltage source which can provide 0 to 10V In all four cases if the REF OUTPUT is connected to the REFERENCE INPUT on the front panel the frequency may be read on the front panel REFERENCE DIGITAL DISPLAY or via the computer interfaces SR510 Guide to Programming The SR510 Lock in Amplifier is remotely programmable via both RS232 and GPIB interfaces It may be used with laboratory computers or simply with a terminal All front panel features except signal input selection and power may be controlled and read via the computer interfaces The SR510 can also read the analog outputs of other laboratory instruments using its four general purpose analog input
122. rly the DTE can tell the DCE that it is not ready by placing 3 VDC on pin 20 DTR of the interface The data lines pins 2 and 3 use negative logic A zero bit is represented by a positive voltage and a one bit is represented by a negative voltage start bit is a positive voltage and a stop bit is a negative voltage Data is transmitted with the least significant bit first The letter which has the ASCII code 41H 0100 0001 would appear as follows e 1 14 ms 9600 Baud waus P man te L LSB 1 m ASC Code Two Stop 40 If a parity option was selected the parity bit would be sent after the 8th data bit but before the first stop bit Final Tip When you are trying to get the RS232 to work with your computer it is helpful to be able to eavesdrop on the RS232 data lines going between the SR510 and the computer This can be done with an ASCII RS232 terminal and the following connector pin 2 3 on RS232 to isten 10 Computer or 58510 To test the connector place the hook clip on pin 2 of the same connector shorting pin 2 to pin 3 Now when you type at the terminal keyboard data transmitted from pin 2 is received at pin 3 and displayed on the terminal screen To use as a debugging tool attach the hook clip to either pin 2 or pin 3 of the RS232 cable on the SR510 to show either data sent from the Computer or the SR510 The baud rate parity and sto
123. s the ratio output An X 5 command will read the ratio output An X 5 command with the parameter v will set port X5 to v volts overriding the ratio output Port X5 will return to the ratio output on power up or reset Y n The Y command reads the status byte See below for a definition of the Status Byte n designates one bit 0 7 of the status byte If n is included the designated bit of the status byte is returned The bit which is read is then reset If n is absent the value of the entire byte is returned and all status bits are then reset This status byte may also be read over the GPIB using the serial poll command 2 The Z command causes internal reset All settings return to their default values The ERR LED will be on for about 2 seconds to indicate that the stored instrument settings are being ignored Ifthe RS232 echo mode is on the sign on message is sent over the RS232 interface Status Byte The SR510 maintains an 8 bit status register which the user may read to obtain information on the unit s status The status byte may be read in two ways by sending the Y command which returns the value of the byte in ASCII coded decimal or when using the GPIB by performing a serial poll The returned status byte reflects all of the status conditions which have occurred since the last time the byte was read After the status byte has been read it is cleared Thus the status byte should be read initially to cle
124. sistor TO 92 Package Transistor TO 92 Package Transistor TO 92 Package Transistor TO 92 Package Transistor TO 92 Package Resistor Carbon Comp 1 4W 596 SR510 PARTS LIST REF SRS part VALUE 254 R102 4 00033 404 100M 255 R103 4 00030 401 10 256 R104 4 00031 401 100 257 R105 4 00031 401 100 258 R108 4 00130 407 1 00 259 R109 4 00199 407 6 81 260 R110 4 00199 407 6 81 261 R111 4 00130 407 1 00K 262 R112 4 00130 407 1 00 263 R113 4 00145 407 110 264 R114 4 00145 407 110 265 R115 4 00047 401 2 2 266 R116 4 00196 407 6 04 267 R117 4 00210 407 9 09 268 R118 4 00130 407 1 00 269 R119 4 00193 407 499 270 R120 4 00180 407 301 271 R121 4 00141 407 100 272 R122 4 00141 407 100 273 R126 4 00210 407 9 09 274 R127 4 00130 407 1 00K 275 R 128 4 00021 401 1 0K 276 R130 4 00082 401 470K 277 R132 4 00082 401 470K 278 R133 4 00179 407 30 1K 279 R134 4 00179 407 30 1K 280 R135 4 00131 407 1 00 281 R138 4 00052 401 20 282 R139 4 00052 401 20 283 R140 4 00150 407 13 0K 284 R141 4 00174 407 280 285 R142 4 00168 407 22 6K 286 R143 4 00150 407 13 0K 287 R144 4 00157 407 16 9K 288 R145 4 00157 407 16 9K 289 R146 4 00193 407 499 290 R147 4 00180 407 301 291 R148 4 00141 407 100 292 R149 4 00141 407 100 293 R150 4 00179 407 30 1K 294 R151 4 00201 407 634 295 R152 4 00195 407 54 9 296 R153 4 00176 407 3 01 297 R154 4 00178 407 3 83 298 R155 4 00211 407 9 53
125. t the output of the PSD is given by Lock In Amplifier DC Amplifier Ouipul Low Pass Filter Vpsd cos wr cos wst 1 2 cos Wr ws t 1 2 cos wr ws t O The sum frequency component is attenuated by the low pass filter and only those difference frequency components within the low pass filter s narrow bandwidth will pass through to the dc amplifier Since the low pass filter can have time constants up to 100 seconds the lock in can reject noise which is more than 0025 Hz away from the reference frequency input For signals which are in phase with the reference the phase control is usually adjusted for zero phase difference between the signal and the reference This can be done by maximizing the output signal A more sensitive technique would be to adjust the phase to null the signal This places the reference oscillator at 90 degrees with respect to the signal The phase control can now be shifted by 90 degrees to maximize the signal Alternatively since the phase control is well calibrated the phase of the signal can be measured by adding 90 degrees to the phase setting which nulls the signal Understanding the Specifications The table below lists some specifications for the SR510 lock in amplifier Also listed are the error contributions due to each of these items The specifications will allow a measurement with a 296 accuracy to be made in one minute We have chosen a reference frequency of 5
126. the reference oscillator is not phase locked to the external reference input This can occur if the reference amplitude is too low the frequency is out of range or the trigger mode is incorrect for the reference signal waveform ERR flashes when an error occurs on one of the computer interfaces such as an incorrect command invalid parameter etc ACT indicates activity on the computer interfaces This LED blinks every time a character is received by the SR510 or transmitted by the SR510 REM indicates that the unit is in the remote state and that the front panel controls are not operative There are two remote states The Remote With Lockout will not allow any inputs from the front panel The Remote Without Lockout command allows you to return the front panel to operation by pressing the DISPLAY UP key Diplay Select The keys in the DISPLAY section select the parameter to be displayed on the output meters and the output on the OUTPUT BNC connector The displayed parameter is indicated by one of the three LED s and can be either the demodulator output X the offset OFST or the rms noise NOISE When displaying NOISE the equivalent noise bandwidth ENBW is selected in the TIME CONSTANT section Output The analog output is available at the OUTPUT BNC The input signal equal to the selected full scale sensitivity will generate a 10V output when the EXPAND function is off With the EXPAND on the output is multiplied by
127. to 100KHz No additional cards are required for the instrument to cover its full frequency range The SR510 can be used to detect a signal at the reference frequency or at twice the reference frequency to allow for convenient measurement of the harmonic of the signal Noise measurement is a feature which allows direct measurement of the noise density of the signal at the reference frequency This is a useful feature to assess at what frequency you should run your experiment Output Filters can have one pole 6 dB per octave or two poles 12 dB octave A two pole filter provides a signal to noise improvement over a single pole filter due to its steeper roll off and reduced noise bandwidth Single pole filters are preferred when the lock in is used in a servo system to avoid oscillation 27 In many servo applications no output filtering is needed In this case the SR510 may be modified to reduce the output time constant to about 20 uS Contact the factory for details Ratio Capability allows the lock in s output to be divided by an external voltage input This feature is important in servo applications to maintain a constant loop gain and in experiments to normalize a signal to the excitation level Computer Interface allows a computer to control and to record data from the instrument This is the single most important feature for extending the lock in s capabilities and it s useful lifetime Measurements which are impractical w
128. to ask for data from the SR510 Your program will wait forever for a response which is not going to come This may not be your fault we have 21 seen Microsoft s Interpreted Basic on the IBM PC occasionally send a curly bracket ASCII 253 when it was supposed to have sent a carriage return ASCII 13 2 Your computer s baud rate has been changed and no longer matches the SR510 s baud rate 3 The initial command sent to the SR510 was invalid due to a garbage character left in the command queue from power up or the first character in you computer s UART is garbage also due to power up It is good practice to send a few carriage returns to the SR510 when your program begins and have your program clear out its UART at the start of your program 4 The SR510 is not sending the correct end of record marker for your computer For example it appears that Microsoft s Rev 3 2 FORTRAN on the IBM PC under DOS 2 1 requires two carriage returns for an end of record marker The J command can be used to set the SR510 end of record marker to 2 carriage returns The end of record marker is that sequence which indicates that the response is complete From the keyboard a single carriage return is the end of record marker 5 Answers are coming back from the SR510 too fast overwriting the end of record markers and causing the computer to hang waiting for a complete response In this case the W command can be used to slow down the
129. tor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Carbon Film 1 4W 5 Resistor Carbon Comp 1 4W 5 Resistor Carbon Comp 1 4W 5 Resistor Carbon Comp 1 4W 5 Resistor Carbon Comp 1 4W 5 Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 0 1 25ppm Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 1 50PPM Resistor Carbon Film 1 4W 5 Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 1 50PPM Resistor Metal Film 1 8W 0 1 25ppm Resistor Metal Film 1 8W 1 50PPM Resistor 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 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
130. tput in 0508 to provide a variable offset and another is the rms noise output Two outputs are not used Expand Amplifier 3 4 U511 is the X10 expand amplifier U516 selects the display and output either the output of U511 or one of the DAC outputs Overload is detected by 1 4 and 2 4 U515 and the signal monitor is driven by 3 4 U515 Front Panel There are 62 led s on the front panel controlled by 8 serial in parallel out shift registers All 8 shift registers are written to simultaneously and 8 consecutive write operations are required to set the LED s The liquid crystal displays are managed by the display controllers U601 and U602 Exclusive or gates U605 and U606 drive the left over segments Octal latch U604 provides the logic bits for these extra segments as well as the keyboard row strobes U603 reads the switch closures as the rows are scanned 32 Microprocessor Control The microprocessor U701 is a Za0A CPU clocked at 4 Mhz 16K bytes of firmware are stored the ROM 0702 0703 is a 2K byte static RAM backed up by a lithium battery A power down standby circuit Q701 preserves the RAM contents when the power is turned off The battery has a life of 5 10 years The CPU has power up and power down resets to prevent erroneous execution during turn on or short sags in the line voltage U704 is a 3 channel counter One channel generates the baud rate for the RS232 interface while the other two are used to measur
131. uations which require the detection of small ac signals Expariment Differential AC Amplifier 1 VRMS A Measurement Example Suppose we wish to measure the resistance of a material and we have the restriction that we must not dissipate very much power in the sample If the resistance is about 0 10 and the current is restricted to 1 uA then we would expect a 100 nV signal from the resistor There are many noise signals which would obscure this small signal 60Hz noise could easily be 1000 times larger and dc potentials from dissimilar metal junctions could be larger still In the block diagram shown below we use a 1Vrms sine wave generator at a frequency wr as our reference source This source is current limited by the 1 MO resistor to provide a 1 uA ac excitation to our 0 10 sample Two signals are provided to the lock in The 1VAC reference is used to tell the lock in the exact frequency of the signal of interest The lock in s Phase Lock Loop PLL circuits will track this input signal frequency without any adjustment by the user The PLL output may be phase shifted to provide an output of cos w t The signal from the sample under test is amplified by a high gain ac coupled differential amplifier The output of this amplifier is multiplied by the PLL output in the Phase Sensitive Detector PSD This multiplication shifts each frequency component of the input signal ws by the reference frequency wr so tha
132. uted until the terminating carriage return is sent An example of a multiple command is G 5 T 1 4 P 45 10 cr It is not necessary to wait between commands The SR510 has a command input buffer of 256 characters and processes the commands in the order received Likewise the SR510 has an output buffer for each interface of 256 characters In general if a command is sent without parameters it is interpreted as a request to read the status of the associated function or setting Values returned by the SR510 are sent as a string of ASCII characters terminated usually by carriage return line feed For example after the above command is sent the following read commands would generate the responses shown below Command Response from the SR510 G cr 5 lt cr gt lt lf gt T 1 lt cr gt 4 lt cr gt lt lf gt P lt cr gt 45 10 lt cr gt lt lf gt The choice of terminating characters sent by the SR510 is determined by which interface is being used and whether the echo feature is in use The terminating sequence for the GPIB interface is always lt cr gt lt lf gt with EOI The default sequence for RS232 is cr when the echo mode is off and lt cr gt lt lf gt when the echo mode is on The terminating sequence for the RS232 interface may be changed using the J command Note that the terminating characters are sent with each value returned by the SR510 Thus the response to the command string G T1 P lt cr gt whi
133. y the operating system generating an error message such as I O Device Error See the W command in the SR510 Command List for another way to slow data transmission Baud Rate The RS232 baud rate of the SR510 is switch selectable from 300 to 19 2K baud see configuration switch setting in the front of this manual 19 2K baud means that data is transmitted at 19 200 bits second With one start bit 2 stop bits 8 data bits and no parity bits each ASCII character requires 573 usec to be 15V sv transmitted 11bits 19 2K baud The typical data string 5 1270 lt cr gt has 7 characters requiring 4 msec to be sent Stop Bits Generally selection of 2 stop bits will result in fewer data transmission errors Parity Parity The Parity bit provides a check against faulty data transfer It is not commonly used in local data transmission environments If the parity option is selected the SR510 will transmit 8 data bits and a parity bit however no parity check of incoming data is done Voltage Levels The RS232 uses bipolar voltage levels 15V Space Binary 0 or Start if Data Line Asserted or On State if Contro Line 49V 0V DC Mark Binary 11 or Stop Bit if Data Line Inhibit or if Control Line 15V The control lines use positive logic For example the DCE tells the DTE that it is clear to send CTS by placing gt 3 VDC on pin 5 of the interface Simila

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