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RF Lock-In Amplifier PDF

255 Pages·2001·1.24 MB·English
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User’s Manual Model SR844 RF Lock-In Amplifier 1290-D Reamwood Avenue Sunnyvale, California 94089 Phone: (408) 744-9040 • Fax: (408) 744-9049 email: [email protected] • www.thinkSRS.com Copyright © 1997 by SRS, Inc. All Rights Reserved. Revision 2.6 (10/2003) Certification Stanford Research Systems certifies that this product met its published specifications at the time of shipment. Stanford Research Systems further certifies that its calibration measurements are traceable to the United States National Institute of Standards and Technology (NIST). Warranty This Stanford Research Systems product is warranted against defects in materials and workmanship for a period of one (1) year from the date of shipment. Service For warranty service or repair, this product must be returned to a Stanford Research Systems authorized service facility. Contact Stanford Research Systems or an authorized representative before returning this product for repair. Information in this document is subject to change without notice. Copyright © Stanford Research Systems, Inc., 1997. All rights reserved. Stanford Research Systems, Inc. 1290-D Reamwood Avenue Sunnyvale, California 94089 Printed in U.S.A. SR844 RF Lock-In Amplifier i Safety and Preparation For Use WARNING! Dangerous voltages, capable of causing injury or death, are present in this instrument. Use extreme caution whenever the instrument cover is removed. Do not remove the cover while the unit is plugged into a live outlet. Caution This instrument may be damaged if operated with the LINE VOLTAGE SELECTOR set for the wrong AC line voltage or if the wrong fuse is installed. Line Voltage The SR844 operates from a 100V, 120V, 220V, or 240V nominal AC power source Selection 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 pull 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 so that the desired voltage is visible when the circuit board is pushed firmly into its slot. Push the fuse-pull lever back into its normal position and insert the correct fuse into the fuse holder. Line Fuse Verify that the correct line fuse is installed before connecting the line cord. For 100V/120V, use a 1 Amp fuse and for 220V/240V, use a 1/2 Amp fuse. Line Cord The SR844 has a detachable, three-wire power cord for connection to the power source and to a protective ground. The exposed metal parts of the instrument are connected to the outlet ground to protect against electrical shock. Always use an outlet which has a properly connected protective ground. Service Do not attempt to service or adjust this instrument unless another person, capable of providing first aid or resuscitation, is present. Do not install substitute parts or perform any unauthorized modifications to this instrument. Contact the factory for instructions on how to return the instrument for authorized service and adjustment. Fan The fans in the SR844 are required to maintain proper operation. Do not block the vents in the chassis or the unit may not operate properly. Warning! Regarding Use With Photomultipliers and Other Detectors The front end amplifier of this instrument is easily damaged if a photomultiplier is used improperly with the amplifier. When left completely unterminated, a cable connected to a PMT can charge to several hundred volts in a relatively short time. If this cable is connected to the inputs of the SR844 the stored charge may damage the front-end op ampls. To avoid this problem, always connect the PMT output to the SR844 input before turning the PMT on. SR844 RF Lock-In Amplifier ii Symbols that may be found on SRS products Symbol Description Alternating current Caution - risk of electric shock Frame or chassis terminal Caution - refer to accompanying documents Earth (ground) terminal Battery Fuse On (supply) Off (supply) SR844 RF Lock-In Amplifier iii Contents General Information Safety and Preparation For Use i Contents iii Specifications v Chapter 1 Getting Started Quick Start 1-3 The Basic Lock-In 1-5 X, Y, R, θ and dBm 1-9 Outputs, Offsets and Expands 1-12 Storing and Recalling Setups 1-18 Aux Outputs and Inputs 1-19 Chapter 2 SR844 Basics What is a Lock-In Amplifier? 2-3 The Functional SR844 2-8 RF Signal Input Path 2-9 Reference Channel 2-10 I.F. Section 2-11 Inside the DSP 2-12 Analog Outputs and Scaling 2-15 What is Dynamic Reserve ? 2-17 Sources of Error 2-19 Using the SR844 as a Double Lock-In 2-22 Noise Measurements 2-23 Intrinsic (Random) Noise Sources 2-24 External Noise Sources 2-25 Chapter 3 Operation Overview 3-3 Signal Input 3-8 Time Constants 3-11 Sensitivity 3-13 CH1 Display and Output 3-15 CH2 Display and Output 3-20 Reference Section 3-26 Save and Recall 3-30 Interface 3-31 Scan and Rel 3-33 Auto Functions 3-40 Shift Functions 3-41 SR844 RF Lock-In Amplifier iv Contents Chapter 4 Programming Index of Commands 4-2 Introduction 4-7 Command Syntax 4-10 Status Register Definitions 4-31 Example Program 4-34 Chapter 5 Testing Getting Ready 5-3 Self Test 5-5 Amplitude Response 5-7 Phase Response 5-9 Frequency Accuracy 5-11 Ref Out Amplitude 5-13 DC Outputs and Inputs 5-15 Input Noise 5-17 SR844 Performance Test Record 5-19 Chapter 6 Circuitry Service 6-3 Circuit Board Locations 6-4 Circuit Descriptions 6-6 Parts Lists 6-25 Schematic Diagrams 6-73 SR844 RF Lock-In Amplifier v Specifications Specifications apply after 30 minutes of warm-up. All specifications are with output filtering enabled (6, 12, 18 or 24 dB/oct) and 2F detection OFF, unless stated otherwise. Signal Input Voltage Input single-ended BNC. Input Impedance 50 Ω or 1 MΩ || 30 pF. Damage Threshold ±5 V (DC+AC) Bandwidth 25 kHz to 200 MHz. Full Scale Sensitivity 100 nV to 1V rms in a 1-3-10 sequence. Gain Accuracy < 50 MHz ±0.25 dB < 200 MHz ±0.50 dB Gain Stability 0.2%/°C Coherent Pickup Low Noise Wide Reserve, Sensitivity < 30 mV. f < 10 MHz < 100 nV (typical) f < 50 MHz < 2.5 µV (typical) f < 200 MHz < 25 µV (typical) Input Noise: 50 Ω Input 100 kHz < f < 100 MHz 2 nV/√Hz (typical), < 4 nV/√Hz (max). 25 kHz < f < 200 MHz < 5 nV/√Hz (typical), < 8 nV/√Hz (max). Input Noise: 1 MΩ Input 25 kHz < f < 200 MHz 5 nV/√Hz (typical), < 8 nV/√Hz (max). Dynamic Reserve > 60 dB (expand off) Reference External Reference Input 25 kHz to 200 MHz. Impedance 50 Ω or 10 kΩ || 40 pF. Level 0.7 Vpp digital or 0 dBm sinusoidal signal. Pulse Width > 2 ns at any frequency. Threshold Setting Automatic, set to midpoint of waveform extrema. Acquisition Time < 10 s (auto-ranging, any frequency). < 1 s (within same octave). Internal Reference Oscillator 25 kHz to 200 MHz. Frequency Resolution 3 digits. Frequency Accuracy ±0.1 in the 3rd digit. Phase Noise -90 dBc/Hz at f=100 MHz, ∆f=100 Hz. Reference Outputs Phase locked to either Internal or External reference. Front Panel Ref Out 25 kHz to 200 MHz square wave, 1.0 Vpp nominal into 50 Ω. Rear Panel TTL Out 25 kHz to 1.5 MHz, 0 to +5 V nominal, ≥ 3 V into 50 Ω. Harmonic Detect Detect at 50 kHz ≤ 2×Reference ≤ 200 MHz. Phase Resolution 0.02° Absolute Phase Error < 50 MHz < 2.5° < 100 MHz < 5.0° < 200 MHz < 10.0° SR844 RF Lock-In Amplifier vi Specifications Reference Relative Phase Error, < 2.5° Orthogonality Phase Noise 0.005° rms at 100 MHz, 100 ms time constant. Phase Drift < 10 MHz < 0.1°/°C < 100 MHz < 0.25°/°C < 200 MHz < 0.5°/°C Demodulator Zero Stability Digital displays have no zero drift. Analog outputs have < 5ppm/°C drift for all dynamic reserve settings. Filtering Time Constants 100 µs to 30 ks with 6, 12, 18 or 24 dB/octave roll-off. None 10 to 20 µs update rate (X and Y outputs), 60 µs (R and θ outputs). Harmonic Rejection Odd Harmonics -10 dBc @ 3×Ref, -14 dBc @ 5×Ref, etc. Other Harmonics and < -40 dBc Sub-harmonics Spurious Responses -10 dBc @ Ref ± 2×IF -23 dBc @ Ref ± 4×IF < -30 dBc otherwise. Displays Channel 1 Channel 2 Reference Type 4½ digit LED 4½ digit LED 4½ digit LED Displayed X Y Reference Frequency Quantities R [Volts] θ [degrees] Reference Phase R [dBm] Y-noise [Volts] Aux Output Voltages X-noise Y-noise [dBm] Offsets in % of Full Scale AUX IN 1 AUX IN 2 IF Frequency Elapsed Settling Time Ratio The signal may be ratioed with respect to AUX IN 1 or 2. The ratio is applied to both X and Y before computation of R, R[dBm], X-noise, Y-noise [V, dBm] and so affects all of these quantities. The ratio input is normalized to 1 V and has a dynamic range > 100. Expand The CH1 and CH2 displays and outputs may be expanded by ×10 or ×100. SR844 RF Lock-In Amplifier Specifications vii CH1 and CH2 Outputs Connectors Front Panel BNC. Voltage Range ±10V full scale proportional to X, Y or CH1, CH2 displayed quantity. ±11V full scale for phase Update Rate X, Y 48 to 96 kHz R, θ, Aux Inputs 12 to 24 kHz X Noise, Y Noise 512 Hz Aux Inputs and Outputs Connectors Rear Panel BNC. Inputs 2 Type Differential with 1 MΩ input impedance on both signal and shield. Range ±10V Resolution 1/3 mV Bandwidth 3 kHz Outputs 2 Range ±10V Resolution 1 mV Environmental Conditions Operating Temperature: +10°C to +40°C (Specifications apply over +18°C to +28°C) Relative Humidity: <90% Non-condensing Non-Operating Temperature: –25°C to +65°C Relative Humidity: <95% Non-condensing General Furnished Accessories Power Cord Operating Manual Interfaces IEEE-488.2 and RS232 interfaces standard. All instrument functions can be controlled and read through either interface. Power 70 Watts, 100/120/220/240 VAC, 50/60 Hz. Dimensions 17" W x 5.25" H x 19.5" D Weight 23 lb. Warranty One year parts and labor on materials and workmanship. SR844 RF Lock-In Amplifier viii SR844 RF Lock-In Amplifier

Description:
Storing and Recalling Setups. 1-18. Aux Outputs and Inputs. 1-19. Chapter 2 SR844 Basics. What is a Lock-In Amplifier? 2-3. The Functional SR844.
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