Geometrics G-822A Operation Manual
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Geometrics G-822A Operation Manual

Cesium magnetometer
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G-822A and G-823A & B
CESIUM MAGNETOMETER
27597-OM REV. B5
Operation Manual
COPYRIGHT © 2004
GEOMETRICS, INC.
2190 Fortune Drive, San Jose, CA 95131 USA
Phone: (408) 954-0522
Fax: (408) 954-0902
EMAIL:
sales@mail.geometrics.com

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  • Page 1 G-822A and G-823A & B CESIUM MAGNETOMETER 27597-OM REV. B5 Operation Manual COPYRIGHT © 2004 GEOMETRICS, INC. 2190 Fortune Drive, San Jose, CA 95131 USA Phone: (408) 954-0522 Fax: (408) 954-0902 EMAIL: sales@mail.geometrics.com...

  • Page 3: Table Of Contents

    Julian Time Enable ................................27 Julian Output format ..............................28 Find Counters .................................28 Set Preamble character ..............................29 Echo Error command ..............................29 Interrogate Setup command ............................29 Analog channels ................................29 Reset command ................................30 Jump to debug ................................30 7.4 Power-up Initialization...............................31 Geometrics, Inc. G-822/G-823 Magnetometer Manual...
  • Page 4 APPENDIX A3. SENSOR INSTALLATIONS .................45 APPENDIX A4. CESIUM-VAPOR SENSOR THEORY ............50 APPENDIX A5. G-822A GENERAL BLOCK DIAGRAM OF SYSTEM COMPONENTS ..54 APPENDIX A6. G-823A GENERAL BLOCK DIAGRAM OF SYSTEM COMPONENTS ..55 APPENDIX A7. G-823B GENERAL BLOCK DIAGRAM OF SYSTEM COMPONENTS ..56 LIST OF FIGURES AND TABLES 1.
  • Page 5 IGURE CHEMATIC DIAGRAM OF DAISY CHAINED COUNTER MODULES 14. G-823B I ............32 IGURE NSTALLED AS BASE STATION MAGNETOMETER 1. G-822A ............. 2 ABLE STANDARD COMPONENT WEIGHTS AND DIMENSIONS 2. T ......................... 13 ABLE ROUBLE SHOOTING 3. G-823A ........... 15...
  • Page 6 Geometrics, Inc. G-822/G-823 Magnetometer Manual...

  • Page 7: Introduction

    The G-823A is simply a G-822A containing additional counter circuitry that internally converts the magnetometer’s analog signal into a digital RS−232 output. Because the G-822A is identical to the G-823A in all other respects, the installation instructions are provided referencing the G-822A only. However they apply to the G-823A as well.

  • Page 8: System Components

    Appendix of this manual. 2.0 SYSTEM COMPONENTS The basic system components of the G-822A consist of the sensor module, a sensor driver module, and an interconnect cable that is permanently attached to the sensor module and detachable from the sensor driver module.

  • Page 9: Performance

    So, at the earth’s surface, in a nominal 50,000nT 1nT equals one gamma or 10 field, the Larmor frequency is about 175 kHz. The output of the G-822A is a continuous sine wave at the Larmor frequency. The typical signal amplitude is from 1 to 2 volts peak-to-peak with the sensor in its optimal orientation.

  • Page 10: Installation

    Like all magnetometers, performance of the G-822A is primarily dependent upon the counting circuitry employed and the quality of the installation procedures. Compensation and/or noise reduction techniques must normally be used to minimize the magnetic effect of the platform and its motion. Navigational and positional errors, radiated electromagnetic noise and heading errors from the aircraft's induced and remnant magnetic fields are typically the major contributors to noise in the survey results.

  • Page 11: Sensor Orientation

    Magnetic fields are vector fields. At any point they are defined by their magnitude and direction. If the G-822A sensor is going to accurately measure the local magnetic field magnitude, it must be properly oriented relative to the local magnetic field direction.
  • Page 12 Earth’s magnetic field is greater or equal to 20º and less than or equal to 75º. There are no restrictions on the direction of travel when using this sensor orientation. Geometrics, Inc. G-822/G-823 Magnetometer Manual...
  • Page 13 Earth’s magnetic field is greater or equal to 65º. There are no restrictions on the direction of travel when using this sensor orientation. Geometrics, Inc. G-822/G-823 Magnetometer Manual...
  • Page 14 The bottom diagram to the left shows the flight directions where the sensor will produce good signal strength. These flight directions are 60º wide and are centered on 45º, 135º, 225º, and 315º. Geometrics, Inc. G-822/G-823 Magnetometer Manual...
  • Page 15 These flight directions are 60 wide and are centered on the cardinal magnetic field directions 0 , 90 , 180 , and Geometrics, Inc. G-822/G-823 Magnetometer Manual...

  • Page 16: Sensor Attachment

    4.2 Sensor attachment An acceptable mount for the G-822A sensor will provide a stable, nonmagnetic attachment to the vehicle, provide vibration dampening and allow the sensor’s orientation to be adjusted with minimal effort. One example of such a mounting solution is the sensor mount available from Geometrics (P/N 27530-01).

  • Page 17: Environmental Considerations

    Special care should be taken in securing or routing the cable so that it does not encounter hard or sharp objects that could damage the cable. Those components used to mount the G-822A sensor or any or any objects near this sensor should be non-magnetic in order to minimize the system heading error.

  • Page 18: Temperature

    Temperature The G-822A is designed to operate over an ambient temperature range of -35 to +50°C. In an enclosed region it may be necessary to providing adequate cooling by free flowing air. If the sensor and electronics are in an unconfined region, convection cooling is generally adequate.

  • Page 19: Trouble Shooting

    6.0 TROUBLE SHOOTING Operation of the G-822A is relatively simple and when trouble arises it is usually easy to recognize and correct. Table 2. is a trouble shooting guide provided to help in quickly locating the probable cause of the most common system problems.

  • Page 20: G-823A Magnetometer

    7. Heater check and adjustment (Authorized Repair Facility only) 7.0 G-823A MAGNETOMETER The addition of Geometrics CM-201 counter assembly board to the G-822A’s sensor driver module transforms the instrument’s analog output signal into RS-232 digital data. With the addition of the CM-201, the instrument is designated as the G-823A. The CM-201 counter...
  • Page 21 Magnetometer power; 24 – 32VDC 30V power Power ground From logging computer, connects to RxD of G-823B To logging computer, connects to TxD of G-823B COMM RS-232 RESET Contact closure to GND EVENT External Trigger Input Geometrics, Inc. G-822/G-823 Magnetometer Manual...

  • Page 22: Cm-201 Output Format

    Figure 12 shows the standard single counter configuration. Commands from the PC are sent out the computer RS-232 transmit pin (TxD) to the counter. Magnetometer and other data are read on the computer receive pin (RxD). Geometrics, Inc. G-822/G-823 Magnetometer Manual Figure 12. Schematic of CM-201, magnetometer, and computer connections...
  • Page 23 If the data were captured to a file and then copied to a line printer the printout would look something like this: $ 99778.131,3749 $ 99890.376,3687 $ 99955.517,3545 $ 99998.293,3472 $100078.835,3329 $100032.071,3381 $ 99979.159,3498 $ 86778.508,3514 $ 78778.216,3645 Geometrics, Inc. G-822/G-823 Magnetometer Manual...

  • Page 24: Commands

    Then the command will be echoed to the next counter (or back to the logging computer if it is the last/only counter in the chain). Subsequent counter modules in multiple counter arrays differentiate between output data and commands by assuming that all characters between the data preamble character ('$' is Geometrics, Inc. G-822/G-823 Magnetometer Manual...
  • Page 25 MS digit of counter # ('0' or '1') 5: x LS digit of counter # ('0' - '9') 6: CR carriage return [Note: characters 4 and 5 can be omitted. If this is done the command will default to counter 0.] Geometrics, Inc. G-822/G-823 Magnetometer Manual...
  • Page 26 2: x format select: 'A'= ASCII (default) 'E'= excess 3 'P'= packed BCD 'S'= Sandia G-822A fmt x: x '0' = Sandia single Mag '1' = Sandia dual Mag 3: CR carriage return [Note: the '0' and '1' 3rd characters are valid only when selecting the Sandia format.
  • Page 27 Syntax err - echo 'ERR' + counter # 2: 'R' 2'cnd char 3: 'R' 3'rd char 4: x MS digit of counter number ('0'-'1') 5: x LS digit of counter number ('0'-'9) 6: ':' colon delimits error message cmd Geometrics, Inc. G-822/G-823 Magnetometer Manual...

  • Page 28: Detailed Command Descriptions

    5 ms resolution. To maintain compatibility with older versions this character is optional. For an example on using this extra precision, the command "C00125" would set the cycle time to 8 hertz (125 ms). A/D channel select/enable Geometrics, Inc. G-822/G-823 Magnetometer Manual...

  • Page 29: Baud Rate Change

    Packed BCD format. An ASCII counter output of: '$ 54369.127,1234,5678,0000' (plus carriage return line feed) converted to hexadecimal numbers would be: 24 20 35 34 33 36 39 2E 31 32 37 2C 31 32 33 34 Geometrics, Inc. G-822/G-823 Magnetometer Manual...
  • Page 30 Note that MagLog and MagLogLite Logging software from Geometrics is designed to receive and decode the Excess 3 data transmission. This is typically used for multiple sensor array systems such as MTADS employed for UXO or archaeological surveys.
  • Page 31 The purpose of this format is to allow customer with existing G-823A Sandia logging software to be able to use the CM-201 without upgrading to new logging software. Note that Geometrics no longer supports the Sandia logging software. The single channel Sandia format is selected with the command string "OS" or "OS0". The dual channel output is selected by the command string "OS1".
  • Page 32 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - A9977813100B3749000000 A9989037600B3687000000 A9995551700B3545000000 A9999829300B3472000000 A0007883500B3329000000 (Note how the most significant '1' A0003207100B3381000000 is truncated for readings greater Geometrics, Inc. G-822/G-823 Magnetometer Manual...

  • Page 33: Julian Time Set

    This command starts/stops the Julian clock. To start the clock on counter 0 the command would be "J100". "1" turns on the clock, while the "00" selects counter 0. To turn off the clock update on counter 2 the command would be "J002". Geometrics, Inc. G-822/G-823 Magnetometer Manual...

  • Page 34: Julian Output Format

    Continuous data output can be inhibited by sending the command 'F01' to the first counter. In this mode there is no first counter (#00) which normally starts data transmission. Data output can be resumed by sending a new 'F00' command. Geometrics, Inc. G-822/G-823 Magnetometer Manual...

  • Page 35: Set Preamble Character

    Counter 1 will modify the command string to "IA01:abcdef" where the letters a-f are either an ASCII '0' (channel off) or '1' (channel on) corresponding to channels 0-5 respectively. If analog channel 0,3, and 4 Geometrics, Inc. G-822/G-823 Magnetometer Manual...

  • Page 36: Reset Command

    If the command string 'XBUG' is received the counter will do a one way jump to factory debug mode where a rudimentary operating system allows probing of registers, ports and memory for debugging purposes. It will only function properly with a single counter module (no daisy chained counters). Geometrics, Inc. G-822/G-823 Magnetometer Manual...

  • Page 37: Power-Up Initialization

    It is also important to provide a ridged support structure so as to keep wind induced motion to a minimum. Figure 14 shows a base station installation that uses a kit supplied by Geometrics for this purpose. Geometrics, Inc.

  • Page 38: Accessory Software

    If, after installing CM-201, further commands are required (such as CLOCK) to configure CM-201 operation to your application, they may be added to the cm201go.cnf file by editing this file with any suitable text editor. Geometrics, Inc. G-822/G-823 Magnetometer Manual...

  • Page 39: Install.bat

    The port number /p:1 would mean use COM1. This parameter is optional. If it not specified COM1 will be used. The interrupt number to use. This parameter is optional. If it is not specified the normal interrupt for the COM port is used. Geometrics, Inc. G-822/G-823 Magnetometer Manual...

  • Page 40: Commflip.exe

    These programs are utility programs that allow the batch files to interact with the user. 9.2 Cesium Sensor Azimuth Program - CsAz CsAz is a DOS program written by Geometrics for users of Cesium magnetometers. The purpose of the program is to determine the proper orientation of the Cesium sensor at various field dip angles of the Earth’s field.
  • Page 41 Try a dip angle of 0 degrees with a tilt of 90 degrees. Try rotating 45 degrees. Even in a horizontal field, one can survey in both north-south and east-west directions. Geometrics sensors are fully automatic hemispheric switching allowing this versatility.

  • Page 42: View201

    00: Each character is sent as it is typed and stored by the counter. When a carriage return is received by the counter the command is executed and then echoed down the daisy chain of counters until it is received back by the View201 program and Geometrics, Inc. G-822/G-823 Magnetometer Manual...

  • Page 43: Function Keys

    This key has effect in graphics mode only. <Alt F1> = Toggle graphics display of Grad1 on/off. Gradient channel 1 is the difference between Mag1 and Mag2. This key has effect in graphics mode only. Geometrics, Inc. G-822/G-823 Magnetometer Manual...
  • Page 44 <F5> = Toggle between graphics and text display mode. <F6> = Lower the magnetometer full scale coefficient in the graphics display window. This key only affects the Mag channels (not gradient). Geometrics, Inc. G-822/G-823 Magnetometer Manual...

  • Page 45: Displaying Analog Channels

    Display channel ON/OFF [0/1]: Type '0' to turn a channel off. No further menu parameters will follow and the channel will stop plotting. Type '1' to turn the display channel on or just <ENTER>, which defaults to on. Geometrics, Inc. G-822/G-823 Magnetometer Manual...

  • Page 46: Counter Number [0-2]

    Set the full-scale value of the display using the "+" and "-" keys. Note that a value of 10000 nT full-scale display as "0000" full scale. All other values display correctly in the allocated 4 digits. Geometrics, Inc. G-822/G-823 Magnetometer Manual...

  • Page 47: Label

    : Bipolar mode, would have been set to "-" for unipolar "1000" : Full scale value. If "0000" is displayed it mean "10000" full scale. "C" : Clipped display, would be a "W" for wrap mode. Geometrics, Inc. G-822/G-823 Magnetometer Manual...
  • Page 48 Geometrics, Inc. G-822/G-823 Magnetometer Manual...

  • Page 49: Appendix A1. Model G-822A Specifications

    APPENDIX A1. MODEL G-822A SPECIFICATIONS Self-oscillating split-beam Cesium Vapor (non- PERATING RINCIPLE radioactive) 20,000 to 100,000 nT PERATING ANGE The earth’s field vector should be at an angle greater PERATING ONES than 6º from the sensor’s equator and greater than 6º...

  • Page 50: Appendix A2. Model G-823A Specifications

    9 pin RS-232 connector and power lugs), lengths to be specified, spare O rings, operation manual and carrying case Optional: Birds, Stingers, Wingtips, Avionics, GPS receivers SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE Geometrics, Inc. G-822/G-823 Magnetometer Manual...

  • Page 51: Appendix A3. Sensor Installations

    APPENDIX A3. SENSOR INSTALLATIONS Figure A1. G-822A sensor and G-822A Bird components Figure A2. Airborne Stinger showing sensor mount. Geometrics, Inc. G-822/G-823 Magnetometer Manual...
  • Page 52 Figure A3. Aircraft fitted with stinger assembly Figure A4. Aircraft fitted with horizontal transverse and longitudinal gradiometer using faired wingtips and stinger. Geometrics, Inc. G-822/G-823 Magnetometer Manual...
  • Page 53 Figure A5. G-822A Boom installation on Ultra-lite autogyro. Figure A6. Single sensor boom installation on Helicopter. Geometrics, Inc. G-822/G-823 Magnetometer Manual...
  • Page 54 Figure A7. Multi-sensor (7) MTADS Helicopter installation for UXO survey. Figure A8. Rack mount for airborne geophysical survey system Geometrics, Inc. G-822/G-823 Magnetometer Manual...
  • Page 55 Figure A9. MTADS multi-sensor array for UXO survey applications. Figure A10. Multi-sensor array on cart for archaeological surveying. Geometrics, Inc. G-822/G-823 Magnetometer Manual...

  • Page 56: Appendix A4. Cesium-Vapor Sensor Theory

    . A separate magnetic field generated by an AC signal applied to a coil inside the sensor is called H1. This coil is shown cross-section along with the other sensor components in Figure A11. Photocell Lamp Lens Lens H1 Coil Filter Absorption Cell Polarizer Figure A11. G-822A cesium-vapor Geometrics, Inc. G-822/G-823 Magnetometer Manual...
  • Page 57 9 levels for the F=4 state and 7 levels for the F=3 state. It is this variation in electron energy level state that is measured to compute the ambient magnetic field strength. Geometrics, Inc. G-822/G-823 Magnetometer Manual...
  • Page 58 In Cesium this Larmor frequency is exactly 3.498572 times the ambient field measured in nano-teslas (gammas). In the G-822A this radio frequency field is generated by a coil, called the H1 coil that is wound around the tube holding the optical components. When the R.F.
  • Page 59 Reversing the direction of the earth field vector (H ) through the sensor requires the drive to the H1 coil to be inverted to obtain oscillation. (See Automatic Hemisphere Switching, section 2.4.3). Geometrics, Inc. G-822/G-823 Magnetometer Manual...

  • Page 60: Appendix A5. G-822A General Block Diagram Of System Components

    APPENDIX A5. G-822A GENERAL BLOCK DIAGRAM OF SYSTEM COMPONENTS G-822 CESIUM MAGNETOMETER 27500-01 CARRYING CASE SHIP KIT APPLICATION G-822 SENSOR OPERATION AND SIG/PWR SPECIFIC MOUNTING & ELECTRONICS TECHNICAL MANUAL CABLE ASSY 27559-01 AND INTERFACE 27502-xx 27597-OM 27565-xx 27615-01 HARDWARE SENSOR DRIVER...

  • Page 61: Appendix A6. G-823A General Block Diagram Of System Components

    APPENDIX A6. G-823A GENERAL BLOCK DIAGRAM OF SYSTEM COMPONENTS G-823A CESIUM MAGNETOMETER 27600-01 SHIP KIT APPLICATION G-822 SENSOR OPERATION AND SIG/PWR SPECIFIC MOUNTING & ELECTRONICS TECHNICAL MANUAL CABLE ASSY 27559-01 AND INTERFACE 27502-xx 27597-OM 27565-xx HARDWARE SENSOR DRIVER SENSOR PACKAGE SENSOR PHYSICS CARRYING CASE ELECTRONICS...

  • Page 62: Appendix A7. G-823B General Block Diagram Of System Components

    APPENDIX A7. G-823B GENERAL BLOCK DIAGRAM OF SYSTEM COMPONENTS G-823B CESIUM MAGNETOMETER 27600-10 SHIP KIT APPLICATION G-822 SENSOR OPERATION AND SIG/PWR SPECIFIC MOUNTING & ELECTRONICS TECHNICAL MANUAL CABLE ASSY 27559-01 AND INTERFACE HARDWARE 27502-xx 27597-OM 27565-xx SENSOR DRIVER SENSOR PACKAGE SENSOR PHYSICS CARRYING CASE ELECTRONICS...

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