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Hinds Instruments PEM200 User Manual

Photoelastic modulator
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PEM200
PHOTOELASTIC MODULATOR
USER MANUAL
Hinds Instruments, Inc.
P/N: 010-0000-095 UM Rev B

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Summary of Contents for Hinds Instruments PEM200

  • Page 1 PEM200 PHOTOELASTIC MODULATOR USER MANUAL Hinds Instruments, Inc. P/N: 010-0000-095 UM Rev B...
  • Page 2 Information furnished by Hinds Instruments, Inc. is believed to be accurate and reliable; however, no responsibility is assumed by Hinds Instruments, Inc. for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent rights of Hinds Instruments, Inc.

  • Page 3: Table Of Contents

    Controller..............Error! Bookmark not defined. 4 Initial Set-Up ......................19 Connecting the PEM Optical Head and Controller ........... 19 Functional Check ......................20 5 PEM200 Software Setup ..................21 Installation ......................21 Setup Running ........................22 Setup Complete ........................ 23 6 PEM200 Control Software ..................
  • Page 4 Exclusions ......................... 64 Overview of the PEM 200 Help System ............. 65 Return For Repair Procedure ................65 Packaging ......................... 66 Items To Include ........................ 66 Shipping Arrangements..................... 66 Return Shipping Address ....................66 Shipping Costs ........................66 PEM200 User Manual...

  • Page 5: Table Of Contents

    Operators’ Safety Summary The general safety information in this summary is for operators of the PEM200 Photoelastic Modulator System. Specific warnings and cautions may be found throughout the manual where they apply, but may not appear in this summary. If the user sees the exclamation point symbol, they need to consult this section of the user manual.
  • Page 6 ON/OFF: The ON/OFF engraving is above the power switch. Ensure the power is off before connecting or disconnecting SMA cables from HV outputs to optical head. More details below. ON/OFF CE Label 24V DC WARNING: HARZARDOUS VOLTAGE: PEM200 User Manual...

  • Page 7: Dc Power Supply

    The appliance inlet or plug on cord should always be positioned to be accessible by the operator. To disconnect all power from the instrument, pull the power cord from the wall outlet or from the appliance inlet. See Operating Space below for detail. PEM200 User Manual...

  • Page 8: Covers

    Section 3 may also lead to these shifts. Any use of the PEM200 outside of the manufacturer intended use, as specified in this manual, could result in safety impairment. PEM200 User Manual...

  • Page 9: Not Required

    Not Required To operate the PEM200, there no requirements for: • Safety Equipment Accessories • Pollution Degree • Ventilation • Flow of air or cooling liquid • Permanently connected equipment • Sound level PEM200 User Manual...

  • Page 10: Unpacking The Pem200

    (503) 690-2000 or email to support@hindsinstruments.com. A return authorization number (RMA) will be assigned to you. See Overview of the PEM200 Help System on page 65 for further contact information. 7. Return approved items to Hinds Instruments Inc. at the following address: Hinds Instruments, Inc.

  • Page 11: Packaging Overview

    Packaging Overview The PEM200 packaging is separated into four sections: • Power Supply Unit • Optical Head • SMA Cable Assembly, Power Cable • PEM-200 Controller Figure S.1 PEM200 Photoelastic Modulator in Shipping Case Unpacking the PEM Optical Head PEM200 User Manual...

  • Page 12: Special Instructions For I/Fs50 Optical Head

    This can be easily removed by hand. Figure S.3 Removal of White Cover on Optical Enclosure • Please save the shipping disk, screws and white cover in the event the PEM needs to be transported. PEM200 User Manual...

  • Page 13: Special Instructions For Series Ii Optical Heads

    Take care when removing a clip near transducer wires. Save clips for future return or transportation of unit. NOTE: DO NOT TURN OPTICAL HEAD OVER WHILE LID IS OFF – OPTICS WILL FALL OUT 3. Replace lid. Extra screws are provided. PEM200 User Manual...

  • Page 14: Series Ii Zs50 & Zs42 Optical Heads

    Take care when removing a clip near transducer wires. Save clips for future return or transportation of unit. NOTE: DO NOT TURN OPTICAL HEAD OVER WHILE LID IS OFF – OPTICS WILL FALL OUT 3. Replace lid. Extra screws are provided. PEM200 User Manual...

  • Page 15: Series Ii Zs37 Optical Heads

    Take care when removing the clip near transducer wires. Save clips for future return or transportation of unit. NOTE: DO NOT TURN OPTICAL HEAD OVER WHILE LID IS OFF – OPTICS WILL FALL OUT 3. Replace lid. Extra screws are provided. PEM200 User Manual...

  • Page 16: Introduction

    FTIR double modulation. The PEM200 principle of operation is based on the photoelastic effect, in which a mechanically stressed sample exhibits birefringence proportional to the resulting strain. Photoelastic modulators are resonant devices, each producing oscillating birefringence at a fixed frequency in the low frequency ultrasound range (20 kHz to 82 kHz).

  • Page 17: Pem-200 Controller

    These connections are necessary to drive the PEM optical head. These are the high voltage SMA connections. Please ensure that the PEM200 controller is off or disconnected from power when making any connection with these SMA ports.

  • Page 18: Pem-200 Controller Rear Panel

    • USB Type B Connection: The USB 2.0 Type B connector interface allows communication to a PC. PEM200 software runs on Windows 7 or 10. • 24V Barrel Input: The barrel connection is the input for a 24VDC power brick.

  • Page 19: Pem-200 Controller Rear Panel Leds

    PEM-200 Controller Rear Panel LEDs • Power: Power will illuminate green whenever the PEM200 controller has power and is on. • Data: The yellow data LED will flash anytime there is communication between the PC and PEM-200 controller. It will illuminate if the controller is attempting to detect connection with the PEM optical head, or if the optical head connected is inappropriate match for the controller hardware.

  • Page 20: Modulator Head Assembly

    Modulator Head Assembly The transducer-optical element assembly (called the “optical assembly”) is the heart of a PEM200 photoelastic modulator. It consists of a rectangular or octagonal “window” of optical material bonded to a quartz piezoelectric transducer. Both optical element and transducer are tuned to the same frequency.
  • Page 21 Figure 3.2 Model II/FS42, II/FS47, II/FS50 Optical Head Figure 3.3 Model II/FS55, II/FS60 Optical Head PEM200 User Manual...
  • Page 22 Figure 3.4 Model II/FS74, II/FS84 Optical Head Figure 3.5 Model II/ZS37, II/ZS42, II/ZS50 Optical Head PEM200 User Manual...

  • Page 23: Controller

    The light source, if unpolarized, is followed by a polarizer at 45 degrees with respect to the horizontal, the modulator with its axis horizontal (0 degrees), a second polarizer (often called the analyzer) at -45 degrees, and a detector. PEM200 User Manual...

  • Page 24: Functional Check

    The detector circuitry deserves some special comment. Care must be taken to ensure adequate frequency response, typically several times the PEM operating frequency. Pre-amplified photo detectors are available from Hinds Instruments that fit this need. page 65 for contacting Hinds Instruments, Inc.

  • Page 25: Pem200 Software Setup

    Installation To begin installation, first download the software installer from https://www.hindsinstruments.com/products/photoelastic-modulators/pem-200/. Download the software package (.zip) on the computer that will control the PEM200. After the download has completed, be sure to unzip the software package before installing. The Graphical User Interface (GUI) is downloaded with a provided Windows Installer (.msi) file.

  • Page 26: Setup Running

    Setup Running After selecting ‘Next’, the setup installs the necessary files onto the computer. The progress is shown through a green status bar. Figure 5.2 PEM-200 Software Installer, Loading PEM200 User Manual...

  • Page 27: Setup Complete

    Once complete, the set up will prompt you to select ‘Finish’, indicating the software has been successfully installed on the computer. Figure 5.3 PEM-200 Software Installer, Finish The PEM Control Software is now installed. There will be a shortcut placed on your desktop with the following icon: PEM200 User Manual...

  • Page 28: Pem200 Control Software

    PEM200 Control Software TheVPEM Control Software allows the user to remotely operate the PEM-200 controller from a PC. This section provides an overview of PEM Control Software installation and the remote operation of the PEM-200 Controller. Setup of the PEM-200 Controller for Use with PEM Control...

  • Page 29: Launching The Pem Control Software And Verifying Communication With The Pem-200 Controller

    Upon opening, the following COM port dialog box will appear: Figure 6.2 COM port dialog box 2. Use the dropdown to select the computer COM port number used by the PEM200 Controller, then press ‘OK’ to open the main window. PEM200 User Manual...

  • Page 30: Main Interface

    This screen allows for adjustments to wavelength and retardation settings as well as provides an update for the resonant frequency. Figure 6.3 PEM200 Control Software Main Interface Wavelength: The wavelength field displays the wavelength setting. Entering a different wavelength can be accomplished two ways: 1.

  • Page 31: Scan Panel

    The retardation and beginning wavelength is set in the main window as described above. Select the View tab and select Show Scan Panel to open the scan panel on the window. Figure 6.4 Accessing Scan Panel PEM200 User Manual...
  • Page 32 Figure 6.5 PEM200 Control and Scan Panel Step Increment: Step increment describes the step size of a wavelength sweep. Entering a different step increment can be accomplished two ways: 1. Double click the step increment displayed to highlight the setting and then enter a new step increment using the keyboard.

  • Page 33: Debug Panel

    Select the View tab and select Show Debug Panel to open the debug panel on the window. Figure 6.6 Accessing PEM200 Control Debug Panel Figure 6.7 PEM200 Control Debug Panel PEM200 User Manual...

  • Page 34: Themes

    Themes The PEM Control Software offers both a light and dark theme. Figure 6.8 PEM200 Control Light Theme Figure 6.9 PEM200 Control Dark Theme Select the View tab and select Use Light/Dark Theme to switch themes. PEM200 User Manual...

  • Page 35: Change Com Port

    Change COM port Select the Settings tab and select Serial Port to change the COM port number to the PEM200 Controller. The serial port dialog box will appear. Use the dropdown to select the appropriate COM port. Figure 6.10 PEM200 Control Serial COM Port Access Figure 6.11 PEM200 Control COM...

  • Page 36: Communication Protocol

    Communication Protocol The Hinds PEM200 controller drives a single PEM at a user selectable amplitude of modulation. The PEM200 communicates over USB as a simple SerialCOM device. The communication protocol is a derivative of the SCPI protocol common to many instruments.
  • Page 37 Trigger are only available with the Synchronous Detector (SD) option. Command Type Note *IDN? Identify the unit :MODulator Root Modulator related command root :DRiVe Set modulator drive voltage as range 0 to 1 :DRiVe? Get modulator drive voltage as range o to 1 PEM200 User Manual...
  • Page 38 Take a measurement of the AUX input voltage :HARMTrig Set Harmonic Trigger :DETActive Set Detector Active :DDeBuG Get Detector Readings :SYStem Root Internal device controls :PEMOutput Set PEM Active or Inactive :IDLE Set PEM to Idle :CPError? Get Current/Phase Error PEM200 User Manual...
  • Page 39 Type Get/Set Purpose Sets the voltage to the modulator on an arbitrary range of 0.0 (lowest modulation amplitude) to 1.0 (highest modulation amplitude) Input example :MOD:DRV 0.1325 Output [DRIVE](1.325000E-1) example Command :MODulator:AMPlitude # Short :MOD:AMP # command PEM200 User Manual...
  • Page 40 :MOD:AMPR? command Type Purpose Reports the modulation amplitude range in nanometers Input example :MOD:AMPR? Output [AMPR](1.000000E+1,5.50000E+2) example Command :MODulator:FREQuency? Short :MOD:FREQ? command Type Purpose Reports the frequency of modulation in Hz Input example :MOD:FREQ? Output [FREQUENCY](5.01930899E+4) example PEM200 User Manual...
  • Page 41 Get/Set Purpose Sets the sampling frequency of the synchronous detector in Hz. The valid range is 1MHz (1e6) to 10MHz (1e7). Suggested and default sample frequency is the suggested 10MHz. Input example :DET:SFREQ 1e6 Output [SCLOCK](1.000000E+6) example PEM200 User Manual...
  • Page 42 Get/Set Purpose Select the channel and harmonic of interest to measure when the synchronous detector is activated. The range of the harmonic is 1 to 5. Input example :DET:HARM 1, 2 (Channel 1, 2f) Output [HARMONIC](1,2) example PEM200 User Manual...
  • Page 43 :DET:FORM Input example :DET:M Output [MXY](1.314652E0, 3.623624E-1,2.1465E-1,1.02436E-4,-9.21565E-5) example Command :DETector:MeasureDC? Short :DET:MDC? command Type Purpose Quickly measure the DC amplitude of the input optical signal. Returns mean and standard deviation. Input example :DET:MDC? Output [DC](1.314652E2, 0.244652E0) example PEM200 User Manual...
  • Page 44 Set the trigger out signal to different harmonics 1f (enter 0) to 4f (enter 3) Input example :DET:HARMT 1 Output [HARMT](1) example Command :DETector:DETActive Short :DET:DETA #, # command Type Purpose Set channel, detector active: 0 off, 1 on Input example :DET:DETA 1, 0 (Channel 1, off) Output [DETACT](1, 0) example PEM200 User Manual...
  • Page 45 Sets modulator active/inactive (on/off) Input example :SYS:PEMO 1 Output [PEMOUT](1) example Command :SYStem:IDLE # Short :SYS:IDLE # command Type Purpose Set the PEM to an idle mode, where PEM will stop dynamically stabilizing. Input example :SYS:IDLE 0 Output [PIDLE](0) example PEM200 User Manual...
  • Page 46 Command :SYStem:CPError? Short :SYS:CPE? command Type Purpose Get current error and phase error as a percentage (0-1 scale) Input example :SYS:CPE Output [CPE](2.500000E-4,1.670000E-3) example PEM200 User Manual...

  • Page 47: Troubleshooting

    Troubleshooting Should you run into any issues with the PEM200 controller, first check that all necessary connections are made: SMA’s between optical head and PEM, 24V power input. Cycle the power and try to communicate with the PEM200. Should power cycling with all connections in place still result in no communication, please contact or call +1-503-690-2000 for assistance.

  • Page 48: Maintenance

    Maintenance Calibration PEM200 modulators are calibrated at the factory before shipment. For most applications, recalibration is neither necessary nor appropriate. For a few applications, however, an on-site calibration procedure will be necessary if optimum performance is to be achieved. Hinds’ engineers will be glad to advise users on whether on site calibration is appropriate in a particular case.

  • Page 49: Cleaning

    These “wet drag” techniques of cleaning are effective methods for removing dust and light residue from most hard-coated optical surfaces. Warning To guard against electrical shock or instrument damage, never allow water to get inside the case. Unplug the unit before cleaning the optics. PEM200 User Manual...
  • Page 50 3. Grasp two free corners of the lens tissue and drag the tissue across the surface away from the junction in a smooth, even manner so the alcohol dries immediately as the rear edge of the tissue moves over the optical surface. PEM200 User Manual...
  • Page 51 This technique may be used regularly to keep residue from building up, preventing damage and degradation to the optical surface. When replacing the cover to the optics, tighten screws (Qty 4) until snug. PEM200 User Manual...

  • Page 52: A Calibration

    3. Where extreme angles of incidence (>15 to 20º) are involved. For user-performed calibration, direct control of the modulator drive commands should be considered (:MOD:DRV #). Calibration Theory The optical setup for most calibration procedures is shown in figure A.1. PEM200 User Manual...
  • Page 53 If there is no birefringence present, the above equations reduce to the following. Note that there is no fundamental (first harmonic) component in the intensity signal. PEM200 User Manual...

  • Page 54: Light Sources For Modulator Calibration

    A brief discussion of light sources suitable for this purpose is in order. Lasers are excellent sources of monochromatic light. At Hinds Instruments, we use HeNe lasers to calibrate most PEMs which we manufacture. Laser beams are intense and well collimated, and do not normally require any focusing optics in the calibration optical setup.

  • Page 55: Calibration Using An Oscilloscope

    Calibration Using an Oscilloscope The most straightforward procedure, and the one used at Hinds Instruments for the factory calibration of modulators, utilizes a monochromatic light source (e.g. HeNe laser), a solid state detector (e.g. silicon photodiode), and an oscilloscope. A block diagram for the setup is given in figure A.2.
  • Page 56 1% can be achieved. Figures A.4 and A.5 show waveforms for retardations slightly less and slightly more than half-wave. Figure A.4 Retardation 90% of Half-wave PEM200 User Manual...

  • Page 57: Multiple Reflection Techniques

    Precise setting of the modulator peak retardation at levels less than half wave may be done by several different methods. For integral fractions of a half-wave, the oscilloscope technique described above may be used by arranging the optical system PEM200 User Manual...

  • Page 58: Static Waveplate Techniques

    Note, for example, the “DC” term in equation 2. For certain values of A (e.g. 2.405 radians), , and therefore the DC term becomes a constant, independent of the birefringence B. The DC intensity also becomes independent of many other changes PEM200 User Manual...
  • Page 59 Addition of a birefringent element as shown in figure A.1, so that a significant 1f signal at the modulator frequency is obtained, will enable determining the controller setting for which . (This occurs for radians.) Detection of the null point is made with a lock-in amplifier at the modulator frequency. PEM200 User Manual...

  • Page 60: Bessel Function Ratio Methods

    3. Adjust the controller until this lock-in output is obtained. The modulator will then be correctly set for quarter-wave operation. A sample calculation is given below for quarter-wave retardation. The required Bessel functions are: π For half-wave: π For quarter wave: PEM200 User Manual...

  • Page 61: Parallel Polarizer Calibration At A Single Wavelength

    From theoretical analysis of the resulting waveforms we learn that: α α − (10) If one plots the ratio V the graph shown in Figure A.9 is obtained. Figure A.9 Ratio V2f/VDC vs retardation, radians PEM200 User Manual...
  • Page 62 A, since the functional relationship is an inverse one. The method, however, requires considerable attention to detail. First, care must be taken to ensure that V is proportional to the average intensity of the modulated light signal. Other contributions to the experimentally measured DC PEM200 User Manual...
  • Page 63 (13) measured The term on the right has a maximum value of 1.481. Using the maximum experimental value of V , equation 13 may be solved for the experimental constant and a PEM200 User Manual...
  • Page 64 A Reference: 1. Kemp, James C., Polarized Light and its Interaction with Modulating Devices, Hinds International, Inc., 1987 2. Oakberg, Theodore C., “Modulated Interference Effects in Photoelastic Modulators”, PEM Newsletter #8, Summer, 1998 PEM200 User Manual...

  • Page 65: B Specifications

    Wavelength (λ ), radian (rad) or degree ( Input / Output Specifications ‘Head’ Connection Connector Style SMA Female – RP-SMA Female Reference Outputs Connector Style SMA Female - Female Output Waveform 5 VDC square wave Output Frequency See ‘Optical Head Specifications’ PEM200 User Manual...

  • Page 66: Environmental

    95% RH non-condensing Operating Altitude 3000 meters Overvoltage Category 40V overvoltage limit Wet Location Pollution Degree Approvals Approved for connection cables not exceeding 3 meters in length. EMC & Safety Standards EN 61326; FCC Class A EN 61010-1 PEM200 User Manual...

  • Page 67: C Optical Head Specifications

    Specifications for models purchased after February 1, 2020 For a full discussion, consult the Useful Aperture Technical Note Please contact Hinds Instruments with your wavelength range for optical calibration Models only available with PEM-100 controller, electronics, and enclosures PEM200 User Manual...

  • Page 68: D User Support Information

    User Support Information Hinds Instruments makes every attempt to ensure that the instruments we provide are products of superior quality and workmanship. We also aim to provide superior technical user support. If you have any questions, or if you encounter problems in the operation of your PEM instrument or system, please contact us.

  • Page 69: Overview Of The Pem 200 Help System

    Overview of the PEM 200 Help System As shown in Table D.1, you can contact Hinds Instruments, Inc. Technical Support in several ways. Method Information Monday - Friday 8:00 AM to 4:00 PM PST Telephone (503) 690-2000 (503) 690-3000 Email sales@hindsinstruments.com...

  • Page 70: Packaging

    If the unit is not under warranty, we will contact you with an estimate of the charges. If you approve of the indicated repairs and cost, Hinds Instruments, Inc. will return your repaired unit after all charges (including parts, labor and return shipping and handling)
  • Page 71 If you do not approve of our proceeding with the repair, then your unit will be returned as is via UPS COD for the amount of the UPS COD freight charges. PEM200 User Manual...
  • Page 72 PEM200 User Manual...

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