SRS Labs SR850 4-17

4-17

allowed), press the [HELP] key. LOC is on when-

ever local front panel control is allowed (usually

on).

SRQ

This indicator is on whenever a GPIB Service

Request is generated by the SR850. SRQ stays

on until a serial poll is completed.

ALT

Indicates that the ALTERNATE keypad is in use.

The ALTERNATE keypad uses the alphabetic leg-

ends printed below each key. To enter the ALT

mode, press the [ALT] key once. Pressing the

keys will now enter letters into the active entry

field. The [0]...[9], [.], [-], [←] and [ALT] have the

same function in the ALTERNATE keypad. To

return to the normal keypad, press the [ALT] key

again.

Screen Display

Contents

Main MODEL SR850 DSP Lock-In Amplifier Stanford Research Systems Page TABLE OF CONTENTS 1-1 GENERAL INFORMATION GETTING STARTED Table of Contents 1-2 TESTING SERVICE CIRCUITRY SAFETY AND PREPARATION FOR USE WARNING 1-3 Page SR850 DSP LOCK-IN AMPLIFIER 1-5 SPECIFICATIONS SR850 DSP Lock-In Amplifier 1-6 1-7 COMMAND LIST 1-8 1-9 1-10 STATUS BYTE DEFINITIONS GETTING STARTED YOUR FIRST MEASUREMENTS Key Types Hardkeys Softkeys Page 2-3 THE BASIC LOCK-IN 2-4 2-5 2-6 2-7 DISPLAYS and TRACES 2-8 2-9 2-10 Page Page 2-13 OUTPUTS, OFFSETS and EXPANDS 2-14 2-15 2-16 2-17 SCANS and SWEEPS 2-18 2-19 2-20 2-21 2-22 2-23 USING THE DISK DRIVE STORING AND RECALLING DATA 2-24 2-25 2-26 2-27 2-28 2-29 STORING AND RECALLING SETTINGS 2-30 2-31 AUX OUTPUTS and INPUTS 2-32 2-33 Page 2-35 TRACE MATH 2-36 2-37 2-38 2-39 2-40 2-41 Page SR850 BASICS Why use a lock-in? What is phase-sensitive detection? WHAT IS A LOCK-IN AMPLIFIER? 3-1 3-2 Narrow band detection Where does the lock-in reference come from? All lock-in measurements require a reference signal. Magnitude and phase WHAT DOES A LOCK-IN MEASURE? RMS or Peak? Degrees or Radians? Page 3-5 THE FUNCTIONAL SR850 SR850 FUNCTIONAL BLOCK DIAGRAM Page 3-7 Reference Input Internal Oscillator REFERENCE CHANNEL Reference Oscillators and Phase Phase Jitter 3-8 Harmonic Detection THE PHASE SENSITIVE DETECTORS (PSD's) 3-9 Digital PSD vs Analog PSD Page 3-11 Time Constants Digital Filters vs Analog Filters TIME CONSTANTS and DC GAIN Synchronous Filters 3-12 Long Time Constants DC Output Gain What about resolution? DC OUTPUTS and SCALING 3-13 X and Y CH1 and CH2 X, Y, R and Output scales 3-14 Trace displays Trace output scaling 3-15 Page 3-17 What is dynamic reserve really? DYNAMIC RESERVE 3-18 Dynamic reserve in the SR850 Minimum dynamic reserve 3-19 Input noise SIGNAL INPUT AMPLIFIER and FILTERS Notch filters 3-20 Anti-aliasing filter Input Impedance 3-21 Single-Ended Voltage Connection (A) INPUT CONNECTIONS 3-22 Current Input (I) AC vs DC Coupling 3-23 Johnson noise INTRINSIC (RANDOM) NOISE SOURCES ( ) Page 3-25 Capacitive coupling Inductive coupling EXTERNAL NOISE SOURCES 3-26 Resistive coupling or ground loops Microphonics Thermocouple effects 3-27 NOISE MEASUREMENTS 3-28 R noise POWER BUTTON FRONT PANEL 4-1 4-2 Front Panel SOFT KEYS KEYPAD SPIN KNOB 4-3 Front Panel Page 4-5 X = 9.7284 mV Y =-1.2050 mV SCREEN DISPLAY 4-6 DATA TRACES 4-7 X = 9.7284 mV SINGLE and DUAL TRACE DISPLAYS Page 4-9 X = 9.7284 mV BAR GRAPHS 4-10 POLAR GRAPHS 4-11 STRIP CHARTS 4-12 4-13 TRACE SCANS, SWEEPS & ALIASING 4-14 4-15 SETTINGS & INPUT/OUTPUT MONITOR MENU DISPLAY 4-16 STATUS INDICATORS 4-17 Page KEYPAD 4-19 8 AUTO SRS 4-20 ADDITIONAL MENUS ENTRY KEYS [START/CONT] and [PAUSE/RESET] 4-21 [CURSOR] [ACTIVE DISPLAY] [MARK] 4-22 [CURSOR MAX/MIN] [AUTO RESERVE] [AUTO GAIN] [AUTO PHASE] 4-23 [PRINT] TO A PRINTER [PRINT] TO A DISK FILE [HELP] [LOCAL] Page 4-25 POWER ENTRY MODULE REAR PANEL 4-26 Rear Panel REAR PANEL BNC CONNECTORS AUX IN 1-4 (A/D Inputs) AUX OUT 1-4 (D/A Outputs) 4-27 Rear Panel TRIG IN TTL OUT PREAMP CONNECTOR Page SR850 MENUS 5-1 5-2 SR850 Menus DEFAULT SETTINGS REFERENCE AND PHASE MENU Reference and Phase 5-3 Reference Phase Auto Phase 5-4 Reference Source 5-5 5-6 Harmonic Sine Output INPUT AND FILTERS MENU Input and Filters 5-7 Source Current Gain 5-8 Input and Filters Menu Grounding Coupling Line Notches GAIN AND TIME CONSTANT MENU Gain and Time Cons 5-9 Sensitivity 5-10 Reserve 5-11 Man Reserve Auto Reserve Time Constant 5-12 Analog Outputs with Short Time Constants 5-13 Filter dB/oct Synchronous Note Page OUTPUT AND OFFSET MENU Output and Offset 5-15 Front Panel CH1 and CH2 5-16 Output and Offset Menu Output Offset and Expand TRACE AND SCAN MENU Trace and Scan 5-17 Trace 5-18 Trace and Scan Menu Sample Rate 5-19 Trace and Scan Menu Scan Length Page DISPLAY AND SCALE MENU Display and Scale 5-21 Format Monitor 5-22 Display and Scale Menu Page Page AUX OUTPUTS MENU Aux Outputs 5-25 Aux Outputs 5-26 Aux Outputs Menu Voltage Sweep Limits 5-27 Aux Outputs Menu Trigger Starts? Page Cursor Seek Cursor Setup CURSOR SETUP MENU 5-29 5-30 Cursor Setup Menu Cursor Width Vert Grid Divs Cursor Control EDIT MARK MENU 5-31 5-32 Edit Mark Menu Edit Mark Delete Mark Cursor to Next MATH MENU Math 5-33 Math Keys 5-34 Smooth 25 point 21 point 17 point 11 point 5 point 5-35 Fit Do Fit Type of Fit View Parameters 5-36 5-37 Left and Right Limit Return 5-38 Calc Do Calc Operation 5-39 Argument Type 5-40 Stats Do Stats Left and Right Limit Disk Keys DISK MENU Disk 5-41 5-42 Save Data 5-43 5-44 Recall Data 5-45 5-46 Save Settings 5-47 Recall Settings 5-48 Disk Utilities SYSTEM SETUP MENU 5-49 System Setup Setup Keys 5-50 Settings Keys Settings 5-51 Setup Communications Output to RS232/GPIB 5-52 Setup GPIB Setup RS232 5-53 View Queues 5-54 Setup Sound Key Click Alarms 5-55 Setup Plotter Plot Mode 5-56 Plot Speed Define Pens 5-57 Setup Printer Printer Type 5-58 Setup Screen Move Right Move Left Move Up Move Down 5-59 Setup Time Time Date Page 5-61 Plot All 5-61 Plot Trace Plot Cursor Plot Abort Return Plot Page 5-63 About the SR850 About SRS Operating Hints Command List Status Bytes Return Info Page 5-65 Keypad Test Keyboard Test Knob Test Test Hardware 5-66 Disk Drive Test RS-232 Test Memory Test Screen Test Printer Test REMOTE PROGRAMMING 6-1 6-2 INTERFACE READY AND STATUS GET (GROUP EXECUTE TRIGGER) 6-3 DETAILED COMMAND LIST correct interface at the beginning of every program. Remember! 6-4 REFERENCE and PHASE COMMANDS Page 6-6 INPUT and FILTER COMMANDS 6-7 GAIN and TIME CONSTANT COMMANDS Page 6-9 OUTPUT and OFFSET COMMANDS 6-10 TRACE and SCAN COMMANDS 6-11 DISPLAY and SCALE COMMANDS 6-12 6-13 CURSOR COMMANDS 6-14 MARK COMMANDS 6-15 AUX INPUT and OUTPUT COMMANDS 6-16 MATH COMMANDS 6-17 6-18 STORE AND RECALL FILE COMMANDS 6-19 SETUP COMMANDS Page Page 6-22 FRONT PANEL CONTROLS and AUTO FUNCTIONS 6-23 DATA TRANSFER COMMANDS 6-24 6-25 6-26 Page 6-28 INTERFACE COMMANDS 6-29 STATUS REPORTING COMMANDS 6-30 STATUS BYTE DEFINITIONS 6-31 6-32 6-33 EXAMPLE PROGRAM 1 Using Microsoft C (v5.1) with the National Instruments GPIB card on the IBM PC. 6-34 6-35 6-36 Page Page 6-39 6-40 6-41 6-42 PERFORMANCE TESTS Introduction [HARDKEYS] <Softkeys> 7-1 7-2 General Installation 7-3 Necessary Equipment Warm Up The Test Record If A Test Fails Page 7-5 1. Self Tests Page 7-7 2. DC Offset Page 7-9 3. Common Mode Rejection Page 7-11 4. Amplitude Accuracy and Flatness 7-12 7-13 5. Amplitude Linearity 7-14 6. Frequency Accuracy Page 7-17 7. Phase Accuracy Page 7-19 8. Sine Output Amplitude Accuracy and Flatness Page 7-21 9. DC Outputs and Inputs 7-22 10. Input Noise Page SR850 Performance Test Record 1. Self Tests 2. DC Offset Page SR850 Performance Test Record 9. DC Outputs and Inputs (continued) 7-27 SR850 Performance Test Record 9. DC Outputs and Inputs (continued) 10. Input Noise 7-28 SR850 SERVICE 8-1 CAUTION CIRCUIT BOARDS Page 8-3 Adjusting the DC Offset and Common Mode Rejection 8-4 8-5 8-6 Adjusting the Notch Filters 8-7 Page CIRCUIT DESCRIPTION CAUTION VIDEO DRIVER AND CRT CIRCUIT BOARDS 9-1 Page CPU BOARD 9-3 9-4 POWER SUPPLY BOARD 9-5 Page DSP LOGIC BOARD 9-7 9-8 ANALOG INPUT BOARD 9-9 9-10 9-11 9-12 9-13 DSP Logic Board Parts List 9-14 9-15 9-16 9-17 9-18 9-19 9-20 Analog Input Board Parts List 9-21 9-22 9-23 9-24 9-25 9-26 9-27 CPU Board Parts List 9-28 9-29 9-30 9-31 9-32 Chassis Assembly Parts List 9-33 9-34 9-35 Miscellaneous Parts List