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3.
PRIOR TO INSTALLATION
3.1 ADJUSTING GAUGE TO THE DESIRED RANGE
embedment strain gauges are supplied fully sealed and pretensioned.
GEOKON
Model 4200 gauges are normally supplied with the wire tension set near the
middle of their range. If the range needs to be adjusted for some reason, the
wire tension may be changed by the following procedure:
1.
Attach the red and black leads to a readout box that has been set to position
D, reading in microstrain.
2.
Grip the small collar under the shrink tube and rotate the end flange as
shown in the figure below.
3.
Rotate clockwise to decrease the initial reading; rotate counterclockwise to
increase the reading. For example, if the gauge will see all compression, it
should be set to about 4000 microstrain.
FIGURE 8: Adjusting the Range of the Strain Gauge
Model 4200-6 / 4200-7 Note: Although the readings are taken on position D,
the digits shown must be converted to microstrain manually. To do this, multiply
the observed digit change by the gauge factor given on the calibration sheet
provided with the strain gauge.
3.2 GAUGE AND CABLE ASSEMBLY
Insert the flat part of the gauge into the slot in the coil assembly located at the
end of the cable. Slide the hose clamp over the assembly and tighten.
FIGURE 9: Assembled Gauge and Coil Housing
Alternatively, the coil housing can be glued in place using cyanoacrylate glue. If
this method is chosen, it will no longer be possible to remove the gauge from
the coil housing.
3.3 PRELIMINARY CHECK
A preliminary check should be performed before installing the gauge in the field.
To perform the preliminary check, complete the following steps:
1.
Using an ohmmeter, check the resistance between the two lead wires
(usually red and black).
MODEL 4200 SERIES STRAIN GAUGES | PRIOR TO INSTALLATION | 5
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