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2.
PRELIMINARY CHECKS
2.1 USING A READOUT
Perform a preliminary check before installing the gauge in the field. To perform
the preliminary check, complete the following steps:
1.
Insert the gauge into the underside of the coil assembly (4100 only).
2.
Connect the gauge leads to a readout box. See Section 6 in necessary.
3.
Observe the displayed readout. The reading should be around the midrange
position as defined in Section 6. The temperature reading should match the
ambient temperature.
Note: Strain gauges are supplied with the wire tension set near midrange;
this gives enough range in both tension and compression to be suitable for
most applications. If adjustment to the strain range is necessary, see
Section 4.1. Under no circumstances should the procedures
described in Section 4.1 be used after the gauge has been welded
down.
4.
Gently pull on the gauge end points; confirm that numbers on the readout
rise as the tension increases. Do not apply excessive tension (greater
than 10 Kgm / 20 lb.), as this may break the vibrating wire!
2.2 USING AN OHMMETER
If a readout is not available, the preliminary checks can be done using an
ohmmeter, as follows:
1.
Check electrical continuity using the ohmmeter. Resistance between the
gauge leads (usually red and black) should be approximately 180 ohms (50
ohms for model 4150 series gauges.)
Note: Be sure to add cable resistance, which is approximately 14.7Ω per
1000 feet (48.5Ω per km) of 22 AWG stranded copper leads at 20 °C.
Multiply this factor by two to account for both directions.
2.
Resistance between thermistor leads (usually green and white) will vary
based on temperature; refer to Appendix C. Resistance between any
conductor and the shield should exceed two megohms.
Should any of these preliminary tests fail, see Section 8 for troubleshooting tips.
MODEL 4100/4150 SERIES VIBRATING WIRE STRAIN GAUGES | PRELIMINARY CHECKS | 3
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