Geokon 4422 User manual

Instruction Manual
Model 4422
Monument Crackmeter
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 ©, 2006-2017 by Geokon, Inc.
(Doc Rev F, 11/27/17)

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
1. INTRODUCTION...................................................................................................................................................1
2. INSTALLATION ....................................................................................................................................................1
2.1 PRELIMINARY TESTS............................................................................................................................................1
2.2 CRACKMETER INSTALLATION..............................................................................................................................2
2.2.1 Drill Hole Type...........................................................................................................................................2
2.2.2 Surface Mounting........................................................................................................................................3
2.3 INITIAL READINGS...............................................................................................................................................3
2.4 CABLE INSTALLATION AND SPLICING ..................................................................................................................3
2.5 LIGHTNING PROTECTION .....................................................................................................................................4
3. TAKING READINGS.............................................................................................................................................5
3.1 GK-404 READOUT BOX.......................................................................................................................................5
3.1.1 Operating the GK-404 ................................................................................................................................5
3.2 GK-405 READOUT BOX.......................................................................................................................................6
3.2.1 Connecting Sensors with 10-pin Bulkhead Connectors Attached...............................................................6
3.2.2 Sensors with Bare Leads.............................................................................................................................6
3.2.3 Operating the GK-405 ................................................................................................................................6
3.3 GK-403 READOUT BOX (OBSOLETE MODEL)......................................................................................................7
3.3.1 Connecting Sensors with 10-pin Bulkhead Connectors Attached...............................................................7
3.3.2 Connecting Sensors with Bare Leads..........................................................................................................7
3.3.3 Operating the GK-403 ................................................................................................................................7
3.4 MEASURING TEMPERATURES...............................................................................................................................7
4. DATA REDUCTION ..............................................................................................................................................8
4.1 DISPLACEMENT CALCULATION............................................................................................................................8
4.2 TEMPERATURE CORRECTION...............................................................................................................................9
4.3 ENVIRONMENTAL FACTORS...............................................................................................................................10
5. TROUBLESHOOTING........................................................................................................................................12
APPENDIX A. SPECIFICATIONS.........................................................................................................................14
A.1 MODEL 4422 CRACKMETER..............................................................................................................................14
A.2 THERMISTOR.....................................................................................................................................................14
APPENDIX B. THERMISTOR TEMPERATURE DERIVATION.....................................................................15

FIGURES
FIGURE 1-MODEL 4422-1 MONUMENT CRACKMETER,GROUTABLE ANCHOR TYPE.................................................... 2
FIGURE 2-MODEL 4422-2 MONUMENT CRACKMETER,SURFACE MOUNTING TYPE..................................................... 3
FIGURE 3-LIGHTNING PROTECTION SCHEME ............................................................................................................... 4
FIGURE 4-LEMO CONNECTOR TO GK-404 ................................................................................................................... 5
FIGURE 5-LIVE READINGS –RAW READINGS............................................................................................................... 6
FIGURE 6-TYPICAL 4422 MONUMENT CRACKMETER CALIBRATION SHEET................................................................11
TABLES
TABLE 1-CRACKMETER READING RANGES.................................................................................................................. 2
TABLE 2-ENGINEERING UNITS CONVERSION FACTORS................................................................................................ 8
TABLE 3-THERMAL COEFFICIENT CALCULATION CONSTANTS .................................................................................... 9
TABLE 4-SAMPLE RESISTANCE ...................................................................................................................................13
TABLE 5-RESISTANCE WORK SHEET...........................................................................................................................13
TABLE 6-THERMISTOR RESISTANCE VERSUS TEMPERATURE......................................................................................15
EQUATIONS
EQUATION 1-DIGITS CALCULATION............................................................................................................................. 8
EQUATION 2-DEFORMATION CALCULATION................................................................................................................ 8
EQUATION 3-THERMALLY CORRECTED DEFORMATION CALCULATION....................................................................... 9
EQUATION 4-THERMAL COEFFICIENT CALCULATION .................................................................................................. 9
EQUATION 5-RESISTANCE TO TEMPERATURE .............................................................................................................15

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1. INTRODUCTION
Geokon Model 4422 Monument Crackmeters are designed to measure movement across joints
and cracks in monuments. The small size is designed to render the crackmeter as unobtrusive as
possible. The shaft of the Monument Crackmeter has three small holes drilled in it. A metal pin
is supplied for insertion inside one of these holes. These holes and the metal pin are designed to
assist the user in selecting the range of the crackmeter so that it can be set to measure mainly
tensions, mainly compressions, or both, depending on which hole the metal pin is inserted. The
maximum range is four mm.
The instrument consists of a vibrating wire sensing element in series with a heat treated, stress
relieved spring, which is connected to the vibrating wire at one end, and to a connecting rod at
the other. As the connecting rod is pulled out from the gage body, the spring is elongated,
causing an increase in tension in the vibrating wire. The increase in tension (strain) of the wire is
directly proportional to the extension of the connecting rod. This change in strain allows the
Monument Crackmeter to measure the opening of a joint very accurately.
Monument Crackmeters are designed to be read by one of the various readout boxes available
from Geokon.
2. INSTALLATION
2.1 Preliminary Tests
Upon receipt of the instrument, the gage should be checked for proper operation (including the
thermistor). The Crackmeter normally arrives with its shaft secured at approximately 50% of its
range, by the metal pin placed inside the middle of the three holes, (see Figure 1). This holds the
instrument in tension in its midrange position. (This also helps protect it during shipping).
CAUTION! Do not rotate the shaft of the Crackmeter more than 180 degrees. This may
cause irreparable damage to the instrument. Never extend the crackmeter beyond its
working range.
Connect the gage to the readout box and take a reading. (See Section 3 for readout instructions.)
The midrange position should give a reading of about 4500 on Channel B. Gently pull on the
ends of the gage and the readings should be stable and in the range of 2000 to 7000 on Channel
B.
Checks of electrical continuity can also be made using an ohmmeter. Resistance between the
gage leads should be approximately 50 ohms, ±5 ohms. Remember to add cable resistance when
checking (22 AWG stranded copper leads are approximately 14.7Ω/1000' or 48.5Ω/km, multiply
by two for both directions). Between the green and white should be approximately 3000 ohms at
25° (see Table 6), and between any conductor and the shield should exceed two megohms.

2
2.2 Crackmeter Installation
The Monument Crackmeter is provided with threaded rods that can be either grouted in short
drill holes or epoxied to the surface. It will normally be found more convenient to fix the cable in
place before the crackmeter is attached.
The crackmeter may be installed at its midrange position by leaving the metal pin in (see Figure
1 and Figure 2 in the following subsections) or the pin may be removed, allowing the initial gage
reading to be set for the anticipated direction of movement. When setting the gage position using
a portable readout, use the reading ranges in Table 1 to determine the proper position.
Approximate Midrange
Reading
Approximate Reading to
Measure Extensions
Approximate. Reading to
Measure Compression
4500-5000
2500-3000
6500-7000
Table 1 - Crackmeter Reading Ranges
2.2.1 Drill Hole Type
For the standard range crackmeter (4 mm), drill two 9 mm (3/8”) diameter holes,
spaced 110 mm (4 3/8”) apart, to a depth of 25 mm (one inch).A drill-hole-spacer-bar
is provided to make this easier. Drill one hole then place a slightly smaller drill in the
hole and use the spacer bar to locate the second hole.
Screw the two stainless steel studs onto the threaded rods, fill the drill holes with epoxy
or quick setting cement, and push the studs into the grout or epoxy with the metal pin
holding the crackmeter at the midrange position still in place. When the grout or epoxy
has hardened then the metal pin can be removed.
Figure 1 - Model 4422-1 Monument Crackmeter, Groutable Anchor Type

3
2.2.2 Surface Mounting
For surface mounting two stainless steel feet are supplied that can be screwed on to the
threaded rods. Prepare some quick setting epoxy and apply to both the surface of the
monument and to the surface of the stainless steel feet. With the metal pin holding the
crackmeter in its midrange position still in place, press the feet down on to the monument
surface and hold in place until the epoxy sets up. Remove the metal pin.
Figure 2 - Model 4422-2 Monument Crackmeter, Surface Mounting Type
2.3 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.
2.4 Cable Installation and Splicing
The cable should be routed to minimize the possibility of damage due to moving equipment,
debris or other causes. The cable can be protected by the use of flexible conduit, which can be
supplied by Geokon.
Terminal boxes with sealed cable entries are available from Geokon for all types of applications.
These allow many gages to be terminated at one location with complete protection of the lead
wires. The interior panel of the terminal box can have built-in jacks or a single connection with a
rotary position selector switch. Contact Geokon for specific application information.
Because the vibrating wire output signal is a frequency rather than a current or voltage,
variations in cable resistance have little effect on gage readings; therefore, splicing of cables has
no ill effects, and in some cases may in fact be beneficial. The cable used for making splices
should be a high quality twisted pair type, with 100% shielding and an integral shield drain wire.
When splicing, it is very important that the shield drain wires be spliced together. Always
maintain polarity by connecting color to color.

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Splice kits recommended by Geokon incorporate casts, which are placed around the splice and
are then filled with epoxy to waterproof the connections. When properly made, this type of splice
is equal or superior to the cable itself in strength and electrical properties. Contact Geokon for
splicing materials and additional cable splicing instructions.
Cables may be terminated by stripping and tinning the individual conductors and then connecting
them to the patch cord of a readout box. Alternatively, a connector may be used which will plug
directly into the readout box or to a receptacle on a special patch cord.
2.5 Lightning Protection
Unlike numerous other types of instrumentation available from Geokon, monument crackmeters
do not have any integral lightning protection components, such as transorbs 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.
Suggested Lightning Protection Options:
•If the instrument 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 the installation of these components.
•Lighting arrestor boards and enclosures are also available from Geokon. These units install
where the instrument cable exits the structure being monitored. The enclosure has a removable
top to allow the customer to service the components or replace the board in the event that the unit
is damaged by a lightning strike. A connection is made between the enclosure and earth ground
to facilitate the passing of transients away from the displacement transducer. See Figure 3.
•Plasma surge arrestors can be epoxied into the instrument cable, close to the transducer. A
ground strap then connects the surge arrestor to an earth ground, such as a grounding stake or the
rebar itself.
Consult the factory for additional information on available lightning protection.
Figure 3 - Lightning Protection Scheme