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Instruction Manual
Model GK-401
Vibrating Wire Readout
No part of this instruction manual may be reproduced, by any means, without the written consent of
Geokon, Inc.
The information contained herein is believed to be accurate and reliable. However, Geokon, Inc. assumes
no responsibility for errors, omissions or misinterpretation. The information herein is subject to change
without notification.
Copyright © 1987, 1995, 2000, 2003 by Geokon, Inc.
(Doc Rev D, 11/03)
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Table of Contents
Summary of Contents for Geokon GK-401
- Page 1 No part of this instruction manual may be reproduced, by any means, without the written consent of Geokon, Inc. The information contained herein is believed to be accurate and reliable. However, Geokon, Inc. assumes no responsibility for errors, omissions or misinterpretation. The information herein is subject to change without notification.
- Page 3 Upon examination by Geokon, if the unit is found to be defective, it will be repaired or replaced at no charge. However, the WARRANTY is VOID if the unit shows evidence of having been tampered with or...
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Page 5: Table Of Contents
..........................4 EADOUT YSTEM 4.3 C ............................4 ALIBRATION APPENDIX A - GK-401 SPECIFICATIONS ....................5 APPENDIX B - CONNECTOR PINOUTS ....................6 APPENDIX C - BATTERY PACK REPLACEMENT INSTRUCTIONS ..........7 APPENDIX D - THERMISTOR LINEARIZATION................8 APPENDIX E - READING OTHER MANUFACTURERS’ SENSORS..........9 TABLES 1 - GK-401 D .............2... -
Page 7: Theory Of Operation
1. THEORY OF OPERATION The GK-401 Vibrating Wire Readout is used to excite and read out vibrating wire gages which include: strain gages, crackmeters, piezometers, total pressure cells, etc. The basic principle is that a wire that is held under tension has a specific natural or resonant frequency of vibration which is dependent on the strain and the length of the wire. -
Page 8: Taking Readings
Generally, positions B, C, D and E are used for all Geokon gages. Position A is used to obtain period of vibration readings for gages in the range of approximately 500 to 5000 Hz. -
Page 9: Data Reduction
3. DATA REDUCTION Individual gage instruction manuals discuss how data is taken, recorded and reduced, but a few important procedures for taking data are noted here. Always take zero or no load readings and record pertinent data which may include but not be limited to: temperature, barometric pressure, weather conditions, water levels, fill levels, nearby construction activity, etc. -
Page 10: Maintenance And Trouble Shooting
(see Appendix A for battery specifications) and installed by the user (see Appendix D for battery replacement instructions). In cases where the battery will no longer operate in the field Geokon should be contacted for remedial measures. 4.2 Readout System If the readout system fails to operate properly, and the cause is not the battery, Geokon should be contacted. -
Page 11: Appendix A - Gk-401 Specifications
APPENDIX A - GK-401 SPECIFICATIONS 450 to 6000 Hz, 170 to 2250 µseconds Excitation Range: 400 to 9500 Hz, 105 to 2500 µseconds Measurement Range: Period: 0.1 µsecond Measurement Resolution: Strain¹: 1 µstrain Accuracy: 0.1% of reading Excitation: 5 volt square wave −20°... -
Page 12: Appendix B - Connector Pinouts
APPENDIX B - CONNECTOR PINOUTS Gage Connector Description Ground Green Clip Lead Gage Positive Red Clip Lead Gage Negative Black Clip Lead Old Style Gage Connector (6 pin, Lemo ERA-1E-306-CNL) Description Ground Green Clip Lead No Connection Gage Positive Red Clip Lead No Connection Gage Negative Black Clip Lead... -
Page 13: Appendix C - Battery Pack Replacement Instructions
(RTV holds it in place very nicely). NOTE: The only screws that should be removed from the outside of the GK-401 are the 8 screws on the face panel and the four screws on the bottom of the box. All... -
Page 14: Appendix D - Thermistor Linearization
APPENDIX D - THERMISTOR LINEARIZATION A thermistor (temperature sensing device) is normally encapsulated with all Geokon vibrating wire sensors. Use an ohmmeter to measure the resistance (usually the green and white leads from the gage cable). The following equation or Table 2 can be used to determine the temperature in degrees centigrade. -
Page 15: Appendix E - Reading Other Manufacturers' Sensors
Most vibrating wire gages available today have frequency characteristics that are within the range of operation of the GK-401 Readout Box, and if they have the type of electromagnetic coil that is used in the pluck and read system of the GK-401, it can be used to read them.