SRS Labs SR850 SR850 DSP LOCK-IN AMPLIFIER, SPECIFICATIONS

SR850 DSP LOCK-IN AMPLIFIER

1-5

SPECIFICATIONS

SIGNAL CHANNEL

Voltage Inputs Single-ended (A) or differential (A-B).

Current Input 106 or 108 Volts/Amp.

Full Scale Sensitivity 2 nV to 1 V in a 1-2-5-10 sequence (expand off).

Input Impedance Voltage: 10 MΩ+25 pF, AC or DC coupled.

Current: 1 kΩ to virtual ground.

Gain Accuracy ±1% from 20°C to 30°C (notch filters off), ±0.2% typical.

Input Noise 6 nV/√Hz at 1 kHz (typical).

Signal Filters 60 (50) Hz and 120(100) Hz notch filters (Q=4).

CMRR 100 dB at 10 kHz (DC Coupled), decreasing by 6 db/octave above 10 kHz

Dynamic Reserve Greater than 100 dB (with no signal filters).

Harmonic Distortion <-90 dB to 10 kHz, <-80 dB to 100 kHz.

REFERENCE CHANNEL

Frequency Range 1 mHz to 102 kHz

Reference Input TTL (rising or falling edge) or Sine.

Sine input is1 MΩ, AC coupled (>1 Hz). 400 mV pk-pk minimum signal.

Phase Resolution 0.001°

Absolute Phase Error <1°

Relative Phase Error <0.001°

Orthogonality 90° ± 0.001°

Phase Noise External synthesized reference: 0.005° rms at 1 kHz, 100 ms, 12 dB/oct.

Internal reference: crystal synthesized, <0.0001° rms at 1 kHz.

Phase Drift <0.01°/°C below 10 kHz

<0.1°/°C to 100 kHz

Harmonic Detect Detect at Nxf where N<32767 and Nxf<102 kHz.

Acquisition Time (2 cycles + 5 ms) or 40 ms, whichever is greater.

DEMODULATOR

Zero Stability Digital displays have no zero drift on all dynamic reserves.

Analog outputs: <5 ppm/°C for all dynamic reserves.

Time Constants 10 µs to 30 s (reference > 200 Hz). 6, 12, 18, 24 dB/oct rolloff.

up to 30000 s (reference < 200 Hz). 6, 12, 18, 24 dB/oct rolloff.

Synchronous filtering available below 200 Hz.

Harmonic Rejection -90 dB

INTERNAL OSCILLATOR

Frequency 1 mHz to 102 kHz.

Frequency Accuracy 25 ppm + 30 µHz

Frequency Resolution 5 digits or 0.1 mHz, whichever is greater.

Frequency Sweeps Linear and Log.

Distortion f<10 kHz, below -80 dBc. f>10 kHz, below -70 dBc.1 Vrms amplitude.

Output Impedance 50 Ω

Amplitude 4 mVrms to 5 Vrms (into a high impedance load) with 2 mV resolution.

(2 mVrms to 2.5 Vrms into 50Ω load).

Amplitude Accuracy 1%

Amplitude Stability 50 ppm/°C

Outputs Sine output on front panel. TTL sync output on rear panel.

When using an external reference, both outputs are phase locked to the

external reference.

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