Geokon 4450 User manual

Instruction Manual
Model 4450
VW Displacement Transducer
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 © 1994-2016 by Geokon, Inc.
(Doc Rev M 11/10/16)

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.

TABLE of CONTENTS
Page
1. INTRODUCTION...........................................................................................................................................1
1.1. THEORY OF OPERATION ...............................................................................................................................1
2. INSTALLATION.............................................................................................................................................1
2.1. PRELIMINARY TESTS ....................................................................................................................................1
2.2. DISPLACEMENT TRANSDUCER INSTALLATION..............................................................................................2
2.3. CABLE INSTALLATION.................................................................................................................................2
2.4. ELECTRICAL NOISE......................................................................................................................................2
2.5. INITIAL READINGS........................................................................................................................................3
2.6. LIGHTNING PROTECTION ..............................................................................................................................3
3. TAKING READINGS.....................................................................................................................................4
3.1. OPERATION OF THE GK-403 READOUT BOX ...............................................................................................4
3.2 OPERATION OF THE GK-404 READOUT BOX .................................................................................................4
3.3 OPERATION OF THE GK-405 READOUT BOX .................................................................................................5
3.4. MEASURING TEMPERATURES ......................................................................................................................5
4. DATA REDUCTION......................................................................................................................................6
4.1. DISPLACEMENT CALCULATION ...................................................................................................................6
4.2. TEMPERATURE CORRECTION.......................................................................................................................7
4.3. ENVIRONMENTAL FACTORS.........................................................................................................................8
5. TROUBLESHOOTING................................................................................................................................10
APPENDIX A - SPECIFICATIONS...............................................................................................................11
A.1. MODEL 4450 DISPLACEMENT TRANSDUCER .............................................................................................11
A.2 THERMISTOR (SEE APPENDIX BALSO)........................................................................................................11
APPENDIX B - THERMISTOR TEMPERATURE DERIVATION............................................................12

LIST of FIGURES, TABLES and EQUATIONS
Page
FIGURE 1-MODEL 4450 DISPLACEMENT TRANSDUCER ..................................................................................... 1
TABLE 1-MODEL 4450 READING VERSUS POSITION IN THE RANGE .................................................................. 2
FIGURE 2-LIGHTNING PROTECTION SCHEME ..................................................................................................... 3
FIGURE 3GK405 READOUT UNIT......................................................................................................................... 5
EQUATION 1-DIGITS CALCULATION..................................................................................................................... 6
EQUATION 2-DISPLACEMENT CALCULATION....................................................................................................... 6
TABLE 2-ENGINEERING UNITS CONVERSION MULTIPLIERS ............................................................................... 6
EQUATION 3-THERMALLY CORRECTED DISPLACEMENT CALCULATION............................................................. 7
EQUATION 4-THERMAL COEFFICIENT CALCULATION.......................................................................................... 7
TABLE 3-THERMAL COEFFICIENT CALCULATION CONSTANTS ........................................................................... 7
FIGURE 4ATYPICAL CALIBRATION SHEET. .......................................................................................................... 9
TABLE A-1 MODEL 4450 DISPLACEMENT TRANSDUCER SPECIFICATIONS....................................................... 11
EQUATION B-1 CONVERT THERMISTOR RESISTANCE TO TEMPERATURE ........................................................ 12
TABLE B-1 THERMISTOR RESISTANCE VERSUS TEMPERATURE ....................................................................... 12

1
1. INTRODUCTION
1.1. Theory of Operation
The instrument consists of a vibrating wire sensing element in series with a heat treated,
stress relieved spring which is connected to the wire at one end and a connecting rod at the
other. The unit is fully sealed and operates at pressures of up to 250 psi. As the connecting
rod is pulled out from the gage body, the spring is elongated causing an increase in tension
which is sensed by the vibrating wire element. The tension in the wire is directly
proportional to the extension, hence, the change in displacement can be determined very
accurately by measuring the strain change with the vibrating wire readout box.
Coil & Thermistor Housing Instrument Cable
Transducer Housing
Alignment Slot
(4 conductor, 22 AWG)
Transducer Shaft
Alignment Pin
Nylon Tie
Figure 1 - Model 4450 Displacement Transducer
CAUTION: Do not rotate the shaft of the Displacement Transducer. This may cause
irreparable damage to the instrument. The alignment pin on the transducer shaft and
slot on the body serve as a guide for alignment.
2. INSTALLATION
2.1. Preliminary Tests
Upon receipt of the instrument, the gage should be checked for proper operation (including
the thermistor The Displacement Transducer normally arrives with it's shaft secured at
approximately 50% of it's range, by either a split PVC sleeve, (for transducers over
100mm (4 inch) range), or a nylon Tyrap, (see Figure 1). This holds the instrument in
tension thereby helping protect it during shipping. Remove this PVC split sleeve or Tyrap
before proceeding. Connect the gage to the Readout to take a reading (see section 3).
The reading should be stable and in the range of 4000 to 5000. When the nylon tie is
removed the reading should be in the range of 2000 to 3000 when the alignment pin rests
on the housing tube (see Figure 1).
When pulling the transducer shaft out to check for proper operation do not extend the
shaft more than the range of the gage!
Checks of electrical continuity can also be made using an ohmmeter. Resistance between
the gage leads should be approximately 180, ±10. Remember to add cable resistance
when checking (22 AWG stranded copper leads are approximately 14.7/1000' or
48.5/km, multiply by 2 for both directions). Between the green and white should be
approximately 3000 ohms at 25° (see Table B-1), and between any conductor and the shield
should exceed 2 megohms.

2
2.2. Displacement Transducer Installation
1. Place the transducer shaft pin into the transducer tube slot first, to prevent twisting the
internal vibrating wire during installation.
2. Rotate the transducer approximately 16 turns to tighten the transducer shaft, with its
#10-32 thread, against the shaft mounting device.
3. Attach the red and black gage leads to the readout box. Select readout in digits
(position "B", see section 3).
4. Gently pull the gage tube, allowing the tube notch to extend away from the shaft pin until
the desired reading is obtained (see Table 1).
5. Hold the desired reading and secure the cable side of the gage against or*inside the
mounting device. Do not rotate the gage tube relative to the shaft while securing. Note:
The transducer may be damaged if its allowed to free-fall through its stroke. (*The
transducer can be secured by using a Swagelok male connector with nylon front and
back ferrules, tightened one full turn beyond fingertight.)
Transducer Digit
Change Minimum Reading Maximum Reading Mid-Range 1/3 Compression
1/3 Extension
1/3 Extension
1/3
Compression
Standard
12, 25, 50 mm 5,000 2000 7000 5000 6500 4000
Slim
12, 25, 50 mm 10,000 3000 13000 8000 6000 9000
Standard
100, 150 mm 5,000 2000 7000 5000 6500 4000
Table 1 - Model 4450 Reading versus Position in the Range
2.3. Cable Installation
The cable should be routed 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.
2.4. 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
2.5. Initial Readings
Initial readings must be taken and carefully recorded along with the temperature at the time
of installation. These readings serve as a reference for subsequent deformation
calculations.
2.6. Lightning Protection
The Model 4450 Vibrating Wire Displacement Transducers, unlike numerous other types of
instrumentation available from Geokon, do not have any integral lightning protection
components, i.e. transzorbs or plasma surge arrestors. Usually this is not a problem
however, 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 install near the
instrument. The enclosure has a removable top 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 2. Consult the factory for additional
information on these or alternate lightning protection schemes.
Plasma surge arrestors can be epoxy potted into the gage cable close to the sensor. A
ground strap would connect the surge arrestor to earth ground, either a grounding stake
or other suitable earth ground such as perhaps the strand to which the transducer is
attached.
Terminal Box/Multiplexer
Instrument Cable LAB-3 Enclosure LAB-3 Board
Model 4450 Transducer
Ground Connections
Surface
(usually buried)
(inside extensometer housing)
Extensometer
Figure 2 - Lightning Protection Scheme

4
3. TAKING READINGS
3.1. Operation of the GK-403 Readout Box
The GK-403 can store gage readings and also apply calibration factors to convert readings
to engineering units. Consult the GK-403 Instruction Manual for additional information on
Mode "G" of the Readout. The following instructions will explain taking gage measurements
using Mode "B".
Connect the Readout using the flying leads or in the case of a terminal station, with a
connector. The red and black clips are for the vibrating wire transducer, the white and green
clips are for the thermistor and the blue for the shield drain wire.
1. Turn on the Readout. Turn the display selector to position "B". Readout is in digits (see
Equation 1).
2. Turn the unit on and a reading will appear in the front display window. The last digit may
change one or two digits while reading. Press the "Store" button to record the value
displayed. If the no reading displays or the reading is unstable see section 5 for
troubleshooting suggestions. The thermistor will be read and output directly in degrees
centigrade.
3. The unit will automatically turn itself off after approximately 2 minutes to conserve power.
3.2 Operation of the GK-404 Readout Box
The GK-404 is a palm sized readout box which displays the Vibrating wire value and the
temperature in degrees centigrade.
The GK-404 Vibrating Wire Readout arrives with a patch cord for connecting to the vibrating
wire gages. One end will consist of a 5-pin plug for connecting to the respective socket on
the bottom of the GK-404 enclosure. The other end will consist of 5 leads terminated with
alligator clips. Note the colors of the alligator clips are red, black, green, white and blue.
The colors represent the positive vibrating wire gage lead (red), negative vibrating wire gage
lead (black), positive thermistor lead (green), negative thermistor lead (white) and
transducer cable drain wire (blue). The clips should be connected to their respectively
colored leads from the vibrating wire gage cable.
Use the POS (Position) button to select position Band the MODE button to select Dg
(digits).
Other functions can be selected as described in the GK404 Manual.
The GK-404 will continue to take measurements and display the readings until the OFF
button is pushed, or if enabled, when the automatic Power-Off timer shuts the GK-404 off.
The GK-404 continuously monitors the status of the (2) 1.5V AA cells, and when their
combined voltage drops to 2V, the message Batteries Low is displayed on the screen. A
fresh set of 1.5V AA batteries should be installed at this point