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Summary of Contents for SRS Labs SR542
- Page 1 Operation and Service Manual Precision Optical Chopper SR542 Stanford Research Systems Revision 1.0 April 7, 2022 •...
- Page 2 Copyright © Stanford Research Systems, Inc., 2022. All rights reserved. Stanford Research Systems, Inc. 1290–D Reamwood Avenue Sunnyvale, CA 94089 USA Phone: (408) 744‑9040 Fax: (408) 744‑9049 • www.thinkSRS.com e‑mail: info@thinkSRS.com • Printed in the U.S.A. Document Number 9‑01764‑903 SR542 Precision Optical Chopper...
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Page 3: Table Of Contents
Service ......2 Symbols on the SR542 ......3 Notation . - Page 4 4.3 Detection at Sum and Difference Frequencies ..68 5 Troubleshooting 5.1 Chopper Head Cable Shield Grounding ... 69 Index SR542 Precision Optical Chopper...
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Page 5: General Information
Service ......Symbols on the SR542 ..... . -
Page 6: Safety And Preparation For Use
AC Line Voltage The SR542 Precision Optical Chopper operates from a 90 V–250 V nom‑ inal AC power source having a line frequency of 50 Hz or 60 Hz. Line Cord The SR542 Precision Optical Chopper has a detachable, three‑wire... -
Page 7: Symbols On The Sr542
Symbols on the SR542 Symbols on the SR542 Warning Risk of electric shock. Injury or death is possible if the instructions are not obeyed. Caution Refer to user manual. Damage to the instrument or other equipment is possible. Caution Injury is possible due to rotating parts. -
Page 8: Specifications
Power < 40 W, 90–250 V ac , 50/60 Hz Dimensions 8.3” × 4.1” × 9.2” (WHL) Controller Head with Shroud 4.31” × 4.65” × 3.75” (WHL) Weight Controller 4.6 lbs Head with Shroud 1.2 lbs SR542 Precision Optical Chopper... -
Page 9: Blade Specifications
Specifications Blade Specifications The chopper blades designed for the SR542 are chemically etched for precision tolerancing of the beam apertures. The blade outer diameter is 4” and thickness is 0.010”. For detailed dimensioning, see Figure 4. For dual‑frequency blades with two tracks of slots (apertures), the tracks are referred to throughout this manual as “inner”... - Page 10 O542DF Variable Duty (10%–90%) Figure 1: Available chopper blades for the SR542. Max beam size for outer (red) and inner (blue) tracks are listed in Table 1. The variable duty factor blade permits selection of duty factor from 10% to 90% in 10% increments depending on the radial placement of the beam spot.
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Page 11: Mechanical Dimensions
Mechanical Dimensions Mechanical Dimensions Controller (a) LEFT (b) FRONT Figure 2: Dimensions (in inches) of the SR542 controller. PROJECT PROJECT SR540 Redesign SR540 Redesign TITLE TITLE asm_top_level_sr542_asm asm_top_level_sr542_asm SIZE SIZE CODE CODE DWG NO DWG NO APPROVED APPROVED CHECKED CHECKED... -
Page 12: Chopper Head
DWG NO APPROVED DRAWN DRAWN Andy Berger Andy Berger 3/16/2022 SCALE 3/16/2022 SCALE WEIGHT WEIGHT SHEET SHEET CHECKED DRAWN Andy Berger 3/16/2022 SCALE WEIGHT SHEET (c) TOP Figure 3: Dimensions (in inches) of the SR542 chopper head. SR542 Precision Optical Chopper... -
Page 13: Chopper Blade
Mechanical Dimensions Chopper Blade The SR542 is compatible with custom custom designs. Figure 4 presents the critical dimensions for compatibility with the chopper hub and opto‑interrupters. Single‑track designs are also supported, for which the outermost aperture track is not needed. The chopper blade thick‑... - Page 14 General Information SR542 Precision Optical Chopper...
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Page 15: Getting Started
1 Getting Started This chapter provides step‑by‑step instructions to get started quickly with the SR542 Precision Optical Chopper. Refer to Chapter 2 for more detailed explanations of the features of the SR542. 1.1 Using This Manual ..... -
Page 16: Using This Manual
A series of step‑by‑step procedures are given for basic operation of the instrument in Section 1.2. Those who prefer to learn the features of the SR542 with greater depth should turn to Chapter 2: Operation. -
Page 17: Lock To Internal Frequency
A long ( ∼ 1 s) press is required to start the motor. On startup, the SR542 first searches for the rotor shaft index, then spins the motor shaft several times to survey the installed blade before pro‑... -
Page 18: Lock To External Frequency
Beginning with the setup described in Section 1.2.1: 1. Press to turn on the SR542. 2. Connect the external reference signal to the Ext Sync Input connec‑ tor on the rear panel using a standard BNC cable (not included). -
Page 19: Use With A Lock-In Amplifier
1.2 Quick Start Guide 1.2.4 Use with a Lock-In Amplifier The SR542 can be used with a lock‑in as a follower or a reference. To follow the lock‑in, simply connect the reference output from the lock‑in to the Ext Sync Input of the SR542 as described above in Section 1.2.3: Lock to External Frequency. - Page 20 SR542 does advance the phase of the photodetector signal, but it advances the phase of the opto‑interrupter signal—used by the lock‑in as its reference—by an identical amount. of the SR542 to 15 ° and notice that the signal on the 10. Set the Phase lock‑in does not change.
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Page 21: Operation
2 Operation This chapter provides an in‑depth look at operation of the SR542. 2.1 Functional Overview ....2.1.1 Chopper Control Loop .... -
Page 22: Functional Overview
(e.g. with a lock‑in amplifier) to identify weak signals in the pres‑ ence of noise and large background. The SR542 provides optical modulation from 0.4 Hz to 20 kHz. By em‑ ploying a brushless, slotless DC motor, mechanical vibrations and phase jitter are dramatically reduced. - Page 23 ) . This is the source �� target control frequency for the selected track (see MFRQ? ). Control Finally, when used with a dual‑frequency chopper blade, the SR542 syn‑ thesizes square wave reference outputs at (�� + �� ) (sum) and OUTER INNER (��...
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Page 24: Chop Mode
(leading by +54 ° mech in this example). 2.1.2.1 Shaft Control First consider the instrument configuration and timing diagram of Fig‑ ure 2.3, in which the SR542 is configured to control the , with a Shaft . The Rotor Shaft Ref Out (one‑pulse‑per‑... -
Page 25: Blade Control: Inner Slots
54 ° mech. Furthermore, due to lateral offsets of the opto‑interrupters which produce Inner Slots Ref Out and Outer Slots Ref Out , the phases of the Inner and Outer signals will be shifted slightly in comparison to the simplified timing diagrams shown here. SR542 Precision Optical Chopper... - Page 26 Figure 2.6 shows that by adjust‑ ing the phase setpoint to +90 ° , the Inner Slots Ref Out can be be brought into phase alignment with Source Out . This amounts to a mechanical phase advanced of +18 ° mech. SR542 Precision Optical Chopper...
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Page 27: Shutter Mode
Phase 2.1.3 Shutter Mode In addition to the traditional chop mode, the SR542 can be used as an optical shutter. While not to be used for precisely timed signals (see the SR475 Laser Shutter for such applications), shutter mode can be use‑... - Page 28 Int Freq Phase VCO FS Source Figure 2.7: With = 0 Hz, the SR542 enters shutter mode, which keeps the Internal Freq Int Freq chopper blade in a fixed position as determined by the setting. The display in this mode presents...
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Page 29: Front Panel Control
2.2 Front Panel Control 2.2 Front Panel Control The SR542 front panel is organized into seven functional blocks which are described in this chapter: Numeric Display, Configuration, Dis‑ play/Adjust, Phase, Numeric Entry, Motor, and Setup. The front panel is shown in Figure 2.8. -
Page 30: Frequency Monitor
For example, with the 10/100 slot blade installed, and the Frequency Monitor set to , holding the down will display: Outer Slots ±8. 8 . 8 . 8 . 8 . 8 . S. C . 100 Releasing will return the display to frequency monitoring. SR542 Precision Optical Chopper... -
Page 31: Settings
(as slot number + angle remainder) can be directly edited via the rotary encoder knob (either the slot number or the angle remainder digits can be selected for direct editing). SR542 Precision Optical Chopper... -
Page 32: Configuration
The Jump to Int feature could be useful to diagnose a noisy Ext Sync signal which the SR542 has difficulty tracking with its Source PLL. With the exception of the Jump to Int function, it is not possible to modify Source while the motor is on. -
Page 33: Edge
FrqErr will be temporarily displayed. 2.2.3.4 Control Control target indicates which periodic feature will be frequency‑ and phase‑locked to the selected Source . The user can select from: Shaft Inner Outer SR542 Precision Optical Chopper... -
Page 34: Display/Adjust
. Any numeric entry button will also cancel the knob functionality and begin numeric entry instead. The knob can only be activated to adjust Settings and will not respond when showing Frequency Monitor selections. SR542 Precision Optical Chopper... -
Page 35: Numeric Entry
2.2 Front Panel Control 2.2.5 Numeric Entry NUMERIC ENTRY keypad is used to directly enter numeric values for the various settings of the SR542. Values are implicitly positive un‑ ± less the button is pressed, which will toggle the sign between pos‑... -
Page 36: Phase
The will only shut off after the chopper head has been de‑energized, so there will be some delay between the “Stop” button press and the LED indicator update. Stop SR542 Precision Optical Chopper... -
Page 37: Setup
When is pressed, the control unit will briefly display the following, indicating that it is saving to the selected non‑volatile memory location: SAVE. . . ±8. 8 . 8 . 8 . 8 . 8 . SR542 Precision Optical Chopper... -
Page 38: Recall
Recall. LOAd. . . will be briefly displayed. Back does not revert changes to the display mode. If the Back operation involves changes to the Source Control , the changes will be rejected if the motor is running. SR542 Precision Optical Chopper... -
Page 39: Rear Panel Connections And Signals
0 to +10 Vdc TTL or Sine Figure 2.9: The SR542 rear panel, with signal inputs and outputs organized into three blocks: Source Inputs and Output, Reference Outputs, and Synthesized Outputs. Also available are a Type‑B USB connector for remote communication and RJ50 connector for the 10P10C chopper head cable. -
Page 40: Source Inputs And Output
2 V amplitude. When the sine input is selected via the Sine trigger edge, the input is AC‑coupled and is unreliable for frequencies <1 Hz. 2.3.1.3 Source Output The BNC connection for Source Output provides a +5 V square wave signal at the frequency of the selected Source SR542 Precision Optical Chopper... -
Page 41: Reference Outputs
− �� OUTER INNER This output provides a +5 V logic signal at the difference of the outer and inner track frequencies. For single‑frequency blades, this output will be identical to Outer Slots Ref Out . SR542 Precision Optical Chopper... - Page 42 2 Operation SR542 Precision Optical Chopper...
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Page 43: Remote Operation
3 Remote Operation This chapter describes operation of the SR542 Precision Optical Chopper via the remote interface. 3.1 List of Commands by Subject ....3.2 List of Commands by Name .... -
Page 44: List Of Commands By Subject
KCLK(?) {z} ..Audible Key Clicks ......51 SR542 Precision Optical Chopper... - Page 45 CHEN(?) [i,] {j} ..Chopper Event Enable ......56 SR542 Precision Optical Chopper...
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Page 46: List Of Commands By Name
EDGE(?) {z} ..External Sync Edge ......46 SR542 Precision Optical Chopper... - Page 47 TOKN(?) {z} ..Token Response Mode ......52 VCOS(?) {f} ..VCO Full‑Scale Frequency ..... . . 48 SR542 Precision Optical Chopper...
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Page 48: Introduction
3.3.2 Remote Interface Buffers The SR542 stores incoming bytes received via the USB interface in a 256‑ byte input buffer. Characters accumulate in the input buffer until a com‑ mand terminator ( ⟨ CR ⟩ or ⟨ LF ⟩ ) is received, at which point the message is parsed and the corresponding command(s) is (are) executed. -
Page 49: Notation
Optional parameter for both set and query forms 3.4.3 Examples Each command is provided with a simple example illustrating its usage. In these examples, all data sent by the host computer to the SR542 are straight teletype font set as... -
Page 50: Configuration Commands
Set (query) the Internal Frequency {to f}, in Hz. »IFRQ 255.17 Example: PHAS(?) {f} Phase Set (query) the phase of the selected Control target, measured in optical degrees. For discussion of valid Phase settings, see Section 2.2.2.2. »PHAS 90.0 Example: SR542 Precision Optical Chopper... -
Page 51: Relp(?) {Z
Set (query) the integer multiplier n of the frequency source {to i = (1, 2, 3,…200)}. »MULT 2 Example: DIVR(?) {i} Frequency Divisor Set (query) the integer divisor m of the frequency source {to i = (1, 2, 3,…200)}. »DIVR? Example: SR542 Precision Optical Chopper... -
Page 52: Vcos(?) {F
+10 V. See Section 2.3.1.1 for further discussion the VCO Input. »VCOS 5000.0 Example: *RST Reset Reset the SR542 to its default configuration. Sending the *RST command is equivalent to sending the following: »MOTR OFF »SRCE INT »EDGE RISE »CTRL OUTER »DISP OUTER... -
Page 53: Chopper Operation Commands
For single‑track blades, i = 0. If SLOT? is queried before running the chopper motor, the returned slot count may be inaccurate. »SLOT? Example: 10, 100 »SLOT? INNER SR542 Precision Optical Chopper... -
Page 54: Setup Commands
0. »*SAV 1 Example: *RCL i Recall Configuration Recall the saved configuration from memory location i =(0, 1,…9). Recall‑ ing from memory location 0 restores the factory default configuration. »*RCL 4 Example: SR542 Precision Optical Chopper... -
Page 55: Back
ON 1 OFF 0 Set (query) the audible alarms {to z = ( »ALRM 1 Example: KCLK(?) {z} Audible Key Clicks ON 1 OFF 0 Set (query) the audible key clicks {to z = ( »KCLK? Example: SR542 Precision Optical Chopper... -
Page 56: Interface Commands
Set (query) the token response mode {to z = ( Token response mode controls the formatting of response messages gen‑ erated by the SR542 to remote queries of token‑type values. When token TOKN OFF response mode is turned off by... -
Page 57: Opc
The set form, *OPC , will set the OPC bit in the Standard Event Status register; the query form, *OPC? , will return the value The *OPC? query response will not be sent by the SR542 until all pre‑ ceding commands have been executed and completed. Equivalently, the *OPC command will not set the OPC bit until all preceding commands have been executed and completed. -
Page 58: Status Commands
Bits in the Status Byte are updated in real time and bits are not cleared when read. Power cycling or *CLS will clear the Status Byte. See also Section 3.5 on the Status Model. »*STB? Example: SR542 Precision Optical Chopper... -
Page 59: Sre(?) [I,] {J
Upon executing *ESR? , the returned bit(s) of the ESR register are cleared. »*ESR? Example: *ESE(?) [i,] {j} Event Status Enable Set (query) the Standard Event Status Enable Register [bit i] {to j}. »*ESE 6, 1 Example: »*ESE? SR542 Precision Optical Chopper... -
Page 60: Chcr? [I]
Upon executing a CHEV? query, the returned bit(s) of the CHEV register are cleared. »CHEV? Example: »CHEV? CHEN(?) [i,] {j} Chopper Event Enable Set (query) the Chopper Event Status Enable Register [bit i] {to j}. »CHEN 3, 1 Example: SR542 Precision Optical Chopper... -
Page 61: Status Model
OPC: Operation Complete Figure 3.1: Status Model for the SR542 Precision Optical Chopper. There are five categories of registers in the status model of the SR542: Condition Registers : These read‑only registers correspond to the real‑time condition of some underlying physical property being monitored. Queries re‑... -
Page 62: Status Byte (Sb) Register
Byte register. 3.5.1 Status Byte (SB) Register The Status Byte is the top‑level summary of the SR542 status model. When enabled by the Service Request Enable register, a bit set in the Status Byte causes the MSS (Master Summary Status) bit to be set. -
Page 63: Standard Event Status Register (Esr)
QYE : Query Error. Indicates data in the output buffer has been lost. DDE : Device‑Dependent Error. Indicates an issue with SR542 configu‑ ration or control signals. EXE : Execution Error. Indicates an error in a command that was suc‑... -
Page 64: Chopper Status (Chcr/Chev) Registers
(CHCR), a pair of transition selection registers (CHPT and CHNT), and the latching event register (CHEV). 3.5.5.1 Chopper Condition Register (CHCR) The Chopper Condition Register consists of 5 condition flags that reflect the real‑time condition of the SR542. Reading the CHCR has no effect on any values. Weight Flag CMAX MON : Motor On. -
Page 65: Chopper Status Enable (Chen) Register
3.5.5.4 Chopper Status Enable (CHEN) Register This is an 8‑bit wide register that masks the CHEV register. The log‑ ical OR of the bitwise AND of CHEV and CHEN produces the CHSB message in the Status Byte register (SB). SR542 Precision Optical Chopper... -
Page 66: Error Codes
3 Remote Operation 3.6 Error Codes The SR542 contains an error buffer that can store up to 32 error codes as‑ sociated with errors encountered during command parsing, command execution, or motor operation. The error LED will illuminate ( when an error occurs for any reason. The errors in the buffer may be read one‑by‑one by executing successive LERR? queries, after which they are... -
Page 67: Command Parsing Errors
41 : Input Buffer Overrun. The input buffer of the remote interface overflowed. All data in the input buffer will be flushed. 42 : Output Buffer Overrun. The output buffer of the remote interface overflowed. All data in the output buffer will be flushed. SR542 Precision Optical Chopper... -
Page 68: Motor Errors
3 Remote Operation 3.6.4 Motor Errors 51 : Chopper head memory fail. On each motor startup, the SR542 attempts to read calibration and identification information from the chopper head. Error 51 indicates that this read operation has failed. Motor startup cannot proceed. Please contact SRS to ar‑... -
Page 69: Applications
4 Applications This chapter discusses common experimental applications of the SR542 Precision Optical Chopper. 4.1 Single Beam Experiment ....4.2 Dual Beam Experiment .... -
Page 70: Single Beam Experiment
Inner/Outer Slots Ref Out BNC connection is used as the Ref In to a lock‑in amplifier. Experiment Source Detector Lock-in Ampli er SR542 Controller Ref In Outer Slots Ref Out Figure 4.1: Single Beam Experiment SR542 Precision Optical Chopper... -
Page 71: Dual Beam Experiment
The use of two modulated optical beams, derived from the same source, enables a ratiometric measurement that can be used to control for fluctu‑ ations in the light source output. The SR542 dual‑frequency blades are made for just this purpose. One of the beams passes through the exper‑... -
Page 72: Detection At Sum And Difference Frequencies
) and (�� − �� OUTER INNER OUTER INNER The SR542 provides synthesized reference outputs at the sum and dif‑ ference frequencies, which can be provided to the reference input of a lock‑in amplifier. Nonlinear Optical Media OUTER Source #1... -
Page 73: Troubleshooting
Do not remove the covers while the unit is plugged into a live outlet. The procedure for adjusting J503 inside the SR542 controller is as fol‑ lows. First, turn off and unplug the unit. Wait one minute after remov‑... - Page 74 5 Troubleshooting SR542 Precision Optical Chopper...
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Page 75: Index
Run/Stop ....32 line ....2, 12, 35 SR542 Precision Optical Chopper... - Page 76 IFRQ ......46 lock‑in ... . 15, 35, 66–68 SR542 Precision Optical Chopper...
- Page 77 *RST ......48 Phase Lock ... 60 SR542 Precision Optical Chopper...
- Page 78 Source ....18, 28 VCOS ..... . . 48 SR542 Precision Optical Chopper...
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