Geokon 4100 Series User manual

©2021, GEOKON. All rights reserved.
Document Revision: HH | Release date: 04/12/21
Model 4100/4150 Series
Vibrating Wire Strain Gauges
Instruction Manual

WARRANTY STATEMENT
GEOKON 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 specifi-
cation, misapplication, misuse or other operating conditions outside of GEOKON's
control. Components that wear or 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 merchant-
ability and of fitness for a particular purpose. GEOKON 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 instal-
lation or use of the product. The buyer's sole remedy for any breach of this agreement
by GEOKON or any breach of any warranty by GEOKON shall not exceed the purchase
price paid by the purchaser to GEOKON 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 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.
No part of this instruction manual may be reproduced, by any means, without the written consent of GEOKON. The
information contained herein is believed to be accurate and reliable. However, GEOKON assumes no responsibility
for errors, omissions or misinterpretation. The information herein is subject to change without notification.
The GEOKON® wordmark and logo are registered trademarks with the United States Patent and Trademark Office.

I
TABLE OF CONTENTS
1. INTRODUCTION............................................................................................................................................1
2. PRELIMINARY CHECKS......................................................................................................................3
2.1 USING A READOUT............................................................................................................................3
2.2 USING AN OHMMETER..................................................................................................................3
3. INSTRUMENT PROTECTION.........................................................................................................4
3.1 CABLE SPLICING AND TERMINATION............................................................................4
3.2 PROTECTION FROM MECHANICAL DAMAGE...........................................................4
3.2.1 SECURING CABLES..........................................................................................................................4
3.2.2 COVER PLATES ..................................................................................................................................4
3.3 CABLE AND CONNECTOR PROTECTION........................................................................6
3.4 PROTECTION FROM CORROSION........................................................................................6
3.5 PROTECTION FROM ELECTRICAL NOISE......................................................................7
3.6 PROTECTION FROM SUNLIGHT AND TEMPERATURE CHANGES .........7
3.7 LIGHTNING PROTECTION............................................................................................................7
4. GAUGE INSTALLATION.......................................................................................................................9
4.1 ADJUSTING THE GAUGE WIRE TENSION ....................................................................9
4.2 INSTALLING THE 4100/4150 VIA SPOT WELDING .............................................9
4.2.1 PREPARE THE SURFACE................................................................................................................9
4.2.2 SPOT WELD TEST STRIPS .............................................................................................................9
4.2.3 SPOT WELDING THE 4100 GAUGE ....................................................................................... 10
4.2.4 SPOT WELDING THE 4150 GAUGE ....................................................................................... 10
4.2.5 WELDING THE SECOND END PIECE..................................................................................... 11
4.2.6 INSTALLING COLLAR SHIMS................................................................................................... 11
4.2.7 INSTALLING THE PLUCKING COIL HOUSING (MODEL 4100 ONLY) ...................... 13
4.2.8 INSTALLING THE GAUGE COVER (MODEL 4150 ONLY).............................................. 13
4.2.9 SECURING THE 4150 GAUGE CABLE................................................................................... 13
4.3 INSTALLING THE 4100/4150 VIA EPOXY BONDING...................................... 13
4.4 INSTALLING THE 4151 STRAIN GAUGE.................................................................... 15
5. GAUGE LOCATION ................................................................................................................................16
5.1 END EFFECTS...................................................................................................................................... 16
5.2 WELDING EFFECTS........................................................................................................................ 16
5.3 BENDING MOMENTS................................................................................................................... 16
6. TAKING READINGS ............................................................................................................................. 20
6.1 STRAIN GAUGE READOUT POSITIONS ...................................................................... 20

II
6.2 GK-404 VIBRATING WIRE READOUT ............................................................................ 20
6.2.1 OPERATING THE GK-404............................................................................................................ 20
6.3 GK-405 VIBRATING WIRE READOUT ............................................................................ 21
6.3.1 CONNECTING SENSORS WITH 10-PIN BULKHEAD CONNECTORS
ATTACHED........................................................................................................................................ 21
6.3.2 CONNECTING SENSORS WITH BARE LEADS ................................................................... 21
6.3.3 OPERATING THE GK-405............................................................................................................ 21
6.4 MEASURING TEMPERATURES............................................................................................ 22
7. DATA REDUCTION................................................................................................................................. 23
7.1 CONVERSION OF THE READINGS TO STRAIN CHANGES ......................... 23
7.2 CONVERTING STRAINS TO STRESSES....................................................................... 23
8. TROUBLESHOOTING........................................................................................................................... 24
APPENDIX A. SPECIFICATIONS................................................................................................... 25
A.1 VIBRATING WIRE STRAIN GAUGE.................................................................................. 25
A.2 THERMISTOR ...................................................................................................................................... 25
APPENDIX B. THEORY OF OPERATION .............................................................................. 26
APPENDIX C. THERMISTOR TEMPERATURE DERIVATION ....................... 28
C.1 3KΩ THERMISTOR RESISTANCE...................................................................................... 28
C.2 10KΩ THERMISTOR RESISTANCE .................................................................................. 29
APPENDIX D. TEMPERATURE CORRECTION WHEN USED ON
CONCRETE..................................................................................................................... 30
APPENDIX E. TEMPERATURE EFFECTS............................................................................. 31
APPENDIX F. CALCULATIONS FROM THREE STRAIN GAUGES,
AT 60 DEGREES, ON A CIRCULAR PIPE ................................... 32
APPENDIX G. MODEL 4150-5 EXTENDED RANGE STRAIN GAUGE 33
APPENDIX H. PARTS LIST.................................................................................................................. 34

III
FIGURES
FIGURE 1: MODEL 4100 VIBRATING WIRE STRAIN GAUGE .........................................1
FIGURE 2: MODEL 4150 VIBRATING WIRE STRAIN GAUGE .........................................2
FIGURE 3: MODEL 4151 VIBRATING WIRE STRAIN GAUGE .........................................2
FIGURE 4: MODEL 4100 COVER PLATE - TOP VIEW ......................................................5
FIGURE 5: MODEL 4150 COVER PLATE - TOP VIEW ......................................................5
FIGURE 6: COVER PLATE - END VIEW ............................................................................5
FIGURE 7: COVER PLATE INSTALLATION, TOP VIEW ....................................................6
FIGURE 8: COVER PLATE INSTALLATION, SIDE VIEW ...................................................6
FIGURE 9: LIGHTNING PROTECTION SCHEME ...............................................................8
FIGURE 10: PEEL TEST ....................................................................................................10
FIGURE 11: SPOT-WELDING SEQUENCE, OUTER ROWS (4100) ................................10
FIGURE 12: SPOT WELDING SEQUENCE, OUTER ROWS (4150) ................................10
FIGURE 13: SPOT WELDING SEQUENCE, INNER ROWS ............................................11
FIGURE 14: USING THE ALIGNMENT TOOL ..................................................................11
FIGURE 15: COLLAR SHIM .............................................................................................12
FIGURE 16: WELDING THE COLLAR SHIM IN PLACE ..................................................12
FIGURE 17: COMPLETED COLLAR SHIM ......................................................................12
FIGURE 18: SPOT WELDED COVER PLATE ...................................................................13
FIGURE 19: MODEL 4151 STRAIN GAUGE INSTALLATION .........................................15
FIGURE 20: STRAIN GAUGES MOUNTED ON CENTRAL WEB ....................................16
FIGURE 21: STRAIN GAUGES MOUNTED ON FLANGES .............................................18
FIGURE 22: AXIAL STRAIN MEASUREMENT/BENDING MOMENT ABOUT YY AXIS .18
FIGURE 23: AXIAL STRAIN AND BENDING MOMENT ABOUT XX AXIS ....................19
FIGURE 24: AXIAL STRAIN AND BENDING MOMENT ABOUT AXIS XX (NOT
RECOMMENDED) ........................................................................................19
FIGURE 25: GK-404 READOUT .......................................................................................20
FIGURE 26: LEMO CONNECTOR TO GK-404 .................................................................20
FIGURE 27: GK-405 READOUT .......................................................................................21
FIGURE 28: GAUGE ASSEMBLY DIMENSIONS .............................................................25
FIGURE 29: COVER ASSEMBLY DIMENSIONS .............................................................25
FIGURE 30: THREE STRAIN GAUGES MOUNTED ON A CIRCULAR PIPE ...................32

IV
TABLES
TABLE 1: GUIDE TO INITIAL TENSION SETTINGS ............................................................9
TABLE 2: STRAIN GAUGE READOUT POSITIONS...........................................................20
TABLE 3: SPECIFICATIONS ...............................................................................................25
TABLE 4: 3KΩ THERMISTOR RESISTANCE .....................................................................28
TABLE 5: 10KΩ THERMISTOR RESISTANCE ...................................................................29
TABLE 6: MODEL 4100/4150 SERIES MODEL AND PARTS LIST..................................34

V
EQUATIONS
EQUATION 1: AXIAL STRESS CALCULATION................................................................. 17
EQUATION 2: STRESS DUE TO BENDING ON AXIS YY ................................................. 17
EQUATION 3: STRESS DUE TO BENDING ON AXIS XX................................................. 17
EQUATION 4: MAXIMUM STRESS .................................................................................. 17
EQUATION 5: THEORETICAL MICROSTRAIN ................................................................. 23
EQUATION 6: STRAIN CALCULATION............................................................................. 23
EQUATION 7: 3KΩ THERMISTOR RESISTANCE............................................................. 28
EQUATION 8: 10KΩ THERMISTOR RESISTANCE........................................................... 29
EQUATION 9: THERMAL CONCRETE STRAINS.............................................................. 30
EQUATION 10: ACTUAL STRAIN ..................................................................................... 30
EQUATION 11: STRAIN DUE TO LOAD CHANGES ONLY ............................................. 30
EQUATION 12: EXTERNAL LOAD STRESS ONLY........................................................... 31
EQUATION 13: FREE FIELD THERMAL STRAINS .......................................................... 31
EQUATION 14: ACTUAL STRAIN ..................................................................................... 31
EQUATION 15: AVERAGE AXIAL STRAIN ....................................................................... 32
EQUATION 16: MAXIMUM BENDING STRAIN AROUND THE YY AXIS ...................... 32
EQUATION 17: MAXIMUM BENDING STRAIN AROUND THE XX AXIS ...................... 32
EQUATION 18: MAXIMUM STRAIN ................................................................................ 32
EQUATION 19: MODEL 4150-5 TEMPERATURE EFFECTS ........................................... 33

VI