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Geokon 1900 Instruction Manual

Magnetic extensometer
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Instruction Manual
Model 1900
Magnetic Extensometer
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 © 1994-2018 by Geokon, Inc.
(Doc Rev H, 04/25/18)

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Summary of Contents for Geokon 1900

  • Page 1 Model 1900 Magnetic Extensometer 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.
  • 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...

  • Page 4: Table Of Contents

    3 - T ....................5 IGURE UIDE OUNTED TO CCESS 4 - U ........................8 IGURE NDERSIDE OF LANGE 5 - C ...................... 8 IGURE LOSE UP OF THE ATTERY TABLES 1 - M 1900 S ........................7 ABLE ODEL PECIFICATIONS...

  • Page 5: Introduction

    1. INTRODUCTION The Model 1900 Magnetic Extensometer is designed to measure movement between magnetic targets anchored in the ground. It is normally installed in a borehole or directly in fill as it is placed. The primary use of the Magnetic Extensometer is the measurement of vertical compression in embankments, foundations, and fills and the movement of settlements in soft ground due to the placement of fills and embankments.
  • Page 6 Anchor points with permanent magnets are anchored in the ground with a continuous access tube passing through their center. A reed switch probe is lowered inside the access tube on the end of a graduated measurement tape, which also contains two electrical conductors. As the probe passes each anchor, the magnets in the anchor cause the reed switch to close, this sounds a buzzer on the tape reel at the surface.

  • Page 7: Installation

    1) Begin by cementing the end cap onto the bottom section of the access tubing using PVC cement (not supplied by Geokon). 2) Using three set screws, tighten the datum magnet onto the bottom section of the access tube about one meter above the bottom end cap.

  • Page 8: Installing The Access Tube Anchor String

    3) Select further sections of access tube and/or telescoping couplings. Position the spider anchors along the sections of access tubing in their desired locations. The spider anchors are attached to the access tube as shown in Figure 2. Figure 2 - Anchor Assembly / Securing the Leaf Springs 4) Use the chains supplied to restrain the ends of the leaf springs).

  • Page 9: Installation In Fills

    This is best done by means of a long push rod (not supplied by Geokon) made from any easily available water pipe with threaded connectors. The push rod assembly when joined should be sufficient length to reach the bottom of the access tube.

  • Page 10: Taking Readings

    3. TAKING READINGS Before taking readings, check the battery voltage by depressing the “TEST” button on the side of the tape storage reel; if no beep is heard the nine-volt alkaline battery needs to be replaced. (See Appendix B for battery replacement instructions.) Access to the battery holder is made by removing the three small screws around the periphery of the tape reel on the side that holds the test button and buzzer.

  • Page 11: Appendix A. Specifications

    ⨉ Datum Magnet Material: PVC Datum Magnet Dimensions: 54 34 mm (2.13" 2.36" 1.34") Borehole Size:² 102-152 mm (4-6") Power: 9V Alkaline Battery Table 1 - Model 1900 Specifications Notes: ¹ Other ranges available on request ² Other sizes available...

  • Page 12: Appendix B. Battery Replacement

    APPENDIX B. BATTERY REPLACEMENT To replace the battery, remove the three screws on the buzzer side flange of the reel. Remove the flange, being careful not to not allow the tape to fall off the reel while doing so. Replace the nine-volt battery Figure 4 Figure 5 with a new one.

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