Geokon 4427 User manual

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Instruction Manual
Model 4427
VW Long Range
Displacement Meter
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 © 2003-2016 by Geokon, Inc.
(Doc Rev J, 11/10/16)

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Warranty Statement
Geokon, Inc. warrants its products to be free of defects in materials and workmanship, under normal use and service
for a period of 13 months from date of purchase. If the unit should malfunction, it must be returned to the factory for
evaluation, freight prepaid. 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 shows evidence of being damaged as a result of excessive corrosion or current, heat, moisture or vibration,
improper specification, misapplication, misuse or other operating conditions outside of Geokon's control.
Components which wear or which are damaged by misuse are not warranted. This includes fuses and batteries.
Geokon manufactures scientific instruments whose misuse is potentially dangerous. The instruments are intended to
be installed and used only by qualified personnel. There are no warranties except as stated herein. There are no other
warranties, expressed or implied, including but not limited to the implied warranties of merchantability and of
fitness for a particular purpose. Geokon, Inc. is not responsible for any damages or losses caused to other equipment,
whether direct, indirect, incidental, special or consequential which the purchaser may experience as a result of the
installation or use of the product. The buyer's sole remedy for any breach of this agreement by Geokon, Inc. or any
breach of any warranty by Geokon, Inc. shall not exceed the purchase price paid by the purchaser to Geokon, Inc.
for the unit or units, or equipment directly affected by such breach. Under no circumstances will Geokon reimburse
the claimant for loss incurred in removing and/or reinstalling equipment.
Every precaution for accuracy has been taken in the preparation of manuals and/or software, however, Geokon, Inc.
neither assumes responsibility for any omissions or errors that may appear nor assumes liability for any damages or
losses that result from the use of the products in accordance with the information contained in the manual or
software.

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TABLE of CONTENTS
1. INTRODUCTION...................................................................................................................................................6
2. SYSTEM COMPONENTS.....................................................................................................................................6
3. INSTALLATION.....................................................................................................................................................7
3.1 PIPE MOUNTED ...................................................................................................................................................7
3.2 PEDESTAL MOUNTED..........................................................................................................................................8
3.3 INSTALLING THE WEAK LINK AND EXTENSION CABLE.......................................................................................9
3.4 CABLE INSTALLATION .......................................................................................................................................9
3.5 ELECTRICAL NOISE..........................................................................................................................................10
3.6. LIGHTNING PROTECTION ................................................................................................................................10
4. TAKING READINGS...........................................................................................................................................11
4.1. OPERATION OF THE GK-403 READOUT BOX .................................................................................................11
4.2. OPERATION OF THE GK404READOUT BOX...................................................................................................11
4.3. OPERATION OF THE GK-405 READOUT BOX .................................................................................................12
4.4 MEASURING TEMPERATURES .........................................................................................................................13
5. DATA REDUCTION ............................................................................................................................................14
5.1. TEMPERATURE CORRECTION.........................................................................................................................14
5.1.1 The transducer alone.................................................................................................................................14
5.1.2 The Extension Cable..................................................................................................................................15
5.2. ENVIRONMENTAL FACTORS............................................................................................................................15
6. TROUBLESHOOTING.......................................................................................................................................18
APPENDIX A - SPECIFICATIONS.......................................................................................................................19
APPENDIX B - THERMISTOR TEMPERATURE DERIVATION....................................................................20

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LIST of FIGURES, TABLES and EQUATIONS
FIGURE 1: SHOWING THE INTERNAL MECHANISM.........................................................................................................6
FIGURE 2: THE WEAK LINK ............................................................................................................................................7
FIGURE 3: MODEL 4427 LONG RANGE DISPLACEMENT METER PIPE MOUNTED.........................................................7
FIGURE 4: MODEL 4427 LONG RANGE DISPLACEMENT METER PEDESTAL MOUNTED ...............................................8
FIGURE 5: ATYPICAL INSTALLATION ON AN UNSTABLE SLOPE.....................................................................................9
FIGURE 6: LIGHTNING PROTECTION SCHEME ............................................................................................................10
FIGURE 7:GK405 READOUT UNIT..............................................................................................................................12
EQUATION 1–DISPLACEMENT CALCULATION............................................................................................................14
EQUATION 3-THERMAL COEFFICIENT CALCULATION................................................................................................15
EQUATION 4–ELONGATION CORRECTION.................................................................................................................15
FIGURE 8: ATYPICAL CALIBRATION SHEET FOR THE 4427 LONG RANGE DISPLACEMENT SYSTEM......................16
FIGURE 9: ATYPICAL CALIBRATION SHEET FOR THE MODEL 4400 TRANSDUCER USED IN THE 4427 SYSTEM....17

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1. INTRODUCTION
The Geokon Model 4427 Long Range Displacement Meter, (LRDM), is designed to measure
displacements of up to 2 meters magnitude between two points. Typical applications include the
monitoring of crack openings due to mining, and the monitoring of unstable slopes.
Figure 1: Showing the internal mechanism
2. SYSTEM COMPONENTS
The Device consists of a drum on which is wound a length of 1/16 inch, nylon-jacketed,
stainless steel aircraft cable. As movement occurs, the cable reels off the drum, and the drum
turns. (The tension on the cable is maintained by a constant force spring inside the drum). The
drum is connected to a lead-screw in such a way that the rotation of the drum is converted into a
linear motion of the lead screw. The lead-screw is connected to a Model 4450 Vibrating Wire
Displacement Transducer, which measures the linear motion. In this way a one-meter
movement of the aircraft cable is converted into roughly 25mm movement of the Transducer.
The whole mechanism is enclosed within a rainproof enclosure as shown in Figures 3 and 4.
A thermistor is included with the Transducer so that temperature changes may be monitored.
The enclosure has a gasketted, hinged cover and is mounted on a 3 inch threaded PVC
pipe flange, which will mate with a 3 inch pipe designed to be installed and grouted inside a
borehole drilled perpendicular to the slope. This standpipe can be provided by the installer or is
available at Geokon.
Also included with the enclosure is a “weak link” for attachment between the tensioned
aircraft cable inside the sensor enclosure and the extension cable, which stretches between the
two points being monitored.

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Figure 2: The weak link
Experience has shown that unless this extension cable is fenced off there is a danger of
large animals or pieces of equipment blundering into it; this can seriously damage the internal
sensor mechanism. Should this happen, the weak link is designed to break at a relatively low
cable tension, thus preventing damage to the mechanism from over-ranging. Also supplied is a
compression spring which absorbs the shock of the recoil of the cable in the event that the weak
link is broken.
3. INSTALLATION
Two styles of installation are available: - pedestal mounted and pipe mounted.
3.1 Pipe Mounted
The Transducer enclosure can be mounted on a 3 inch steel pipe threaded at its upper end
to mate with the flange on the underside of the sensor enclosure. In the case of an unstable
slope the enclosure will probably be at the up-hill point and the 3 inch pipe will be grouted or
firmly wedged into a borehole drilled perpendicular to the slope. The second moving point
should consist of a similar 3 inch pipe grouted or wedged in place at the desired distance from
the first mounting point. Figure 3 shows a typical set-up
Figure 3: Model 4427 Long Range Displacement Meter pipe mounted

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3.2 Pedestal Mounted
At locations where drilling a hole is not possible the readout enclosure can be mounted on a
pedestal. Here the Transducer Enclosure is bolted to a steel Mounting Plate which is then
bolted to a flat surface measuring about 9 inch square. Ideally, the plane of this surface should
be inclined to be parallel to the plane of the extension wire; (in the case of measurements down
a slope this would mean parallel to the slope). Once this surface has been created, in wood or
concrete then four bolt holes need to be drilled in it with the same bolt pattern as the four 3/8
inch holes drilled in the Mounting Plate, these holes are then used to install ¼ inch Rawl drop in
anchors for concrete, (available through Geokon), or ¼ inch lag screws in wood. A typical set up
is shown in figure 4 on the next page. Instructions for the Rawl drop-in anchors are as follows:
1. Using a masonry drill or other suitable equipment, drill two 3/8 inch, (or 10mm), diameter
holes 1¼", (32mm), deep at the proper locations.
2. Insert the expansion anchors into the holes, with the slotted end down and then, insert
the setting tool provided, small end first, into the anchor and expand the anchor by
hitting the large end of the setting tool with several sharp hammer blows.
Figure 4: Model 4427 Long Range Displacement Meter pedestal mounted

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3.3 Installing the weak link and extension cable
The extension cable is used to cover the distance between the two points. A length of plastic
coated 1/16 inch aircraft cable is supplied for this purpose. The cable has two loops which are
shipped loosely held by two cable clamps. When the Transducer enclosure has been installed
and the remote anchoring station, attach the extension cable to the anchor station and tighten
the two cable clamps. Using the snap-swivel hooks the ends of the weak link, hook the weak
link onto the extension cable loop and on to the end loop of the cable wound on the drum in the
enclosure.
Adjust the extension cable length by pulling cable through the two cable clamps until the
wire is tight and the wire tension is taken by the drum. Connect the readout cable to the readout
box, and pull about 4 inches of cable off the drum so that there is some movement of the
transducer as revealed by a change of reading on the readout box. Tighten the two extension
cable clamps and the two clamps on the weak link assembly.
3.4 Cable Installation
The cable should be routed and protected in such a way so as to minimize the possibility of
damage due to moving equipment, debris or other causes. Cables may be spliced to lengthen
them, without affecting gage readings. Always waterproof the splice completely, preferably
using an epoxy based splice kit such the 3M Scotchcast, model 82-A1. These kits are
available from the factory.
Figure 5: A typical installation on an unstable slope

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3.5 Electrical Noise
Care should be exercised when installing instrument cables to keep them as far away as
possible from sources of electrical interference such as power lines, generators, motors,
transformers, arc welders, etc. Cables should never be buried or run with AC power lines. The
instrument cables will pick up the 50 or 60 Hz (or other frequency) noise from the power cable
and this will likely cause a problem obtaining a stable reading. Contact the factory concerning
filtering options available for use with the Geokon dataloggers and readouts should difficulties
arise.
3.6. Lightning Protection
The Model 4427 Vibrating Wire Long Range Displacement Meter, can be supplied with integral
lightning protection components, i.e. transzorbs or plasma surge arrestors. If the instrument
cable is exposed, it may be appropriate to install lightning protection components, as the
transient could travel down the cable to the gage and possibly destroy it.
Note the following suggestions;
If the gage is connected to a terminal box or multiplexer components such as plasma surge
arrestors (spark gaps) may be installed in the terminal box/multiplexer to provide a measure
of transient protection. Terminal boxes and multiplexers available from Geokon provide
locations for installation of these components.
Lighting arrestor boards and enclosures are available from Geokon that can be installed
inside the enclosure. The enclosure has a hinged lid, so, in the event the protection board
(LAB-3) is damaged, the user may service the components (or replace the board). A
connection is made between this enclosure and earth ground to facilitate the passing of
transients away from the gage. See Figure 3. Consult the factory for additional information
on these or alternate lightning protection schemes.
Alternatively, plasma surge arrestors can be included inside the enclosure close to the
sensor. A ground strap would connect the surge arrestor to earth ground, either a
grounding stake or other suitable earth ground.
Terminal Box/Multiplexer
Instrument Cable LAB-3 Enclosure LAB-3 Board
Model 4450 Transducer
Ground Connections
Surface
(usually buried)
(inside extensometer housing)
Extensometer
Figure 6: Lightning Protection Scheme