Geokon 4580, Instruction Manual

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3.3 GK-403 Readout Box (Obsolete Model)
The GK-403 can store gauge readings as well as apply calibration factors to convert readings to
engineering units. The following instructions explain taking gauge measurements using Modes
“B” and “F”.
3.3.1 Connecting Sensors with a 10-pin Bulkhead
Align the grooves on the sensor connector (male), with the appropriate connector on the
readout (female connector labeled senor or load cell). Push the connector into place, and
then twist the outer ring of the male connector until it locks into place.
3.3.2 Connecting Sensors with Bare Leads
Attach the GK-403-2 flying leads to the bare leads of a Geokon vibrating wire sensor by
connecting each of the clips on the leads to the matching colors of the sensor conductors,
with blue representing the shield (bare).
3.3.3 Operating the GK-403
1) Turn the display selector to position “B” (or “F”).
2) Turn the unit on.
3) The readout will display the vibrating wire output in digits (refer to Equation 1 in
Section 4). The last digit may change one or two digits while reading.
4) The thermistor reading will be displayed above the gauge reading in degrees
centigrade.
5) Press the “Store” button to record the value displayed.
If the no reading displays or the reading is unstable, see Section 6 for troubleshooting
suggestions. The unit will automatically turn off after approximately two minutes to
conserve power. Consult the GK-403 Instruction Manual for additional information.
3.4 Measuring Temperatures
All vibrating wire transducers are equipped with a thermistor, which gives a varying resistance
output as the temperature changes. The white and green leads of the instrument cable are
normally connected to the internal thermistor. Geokon readout boxes will read the thermistor and
display the temperature in degrees C. (High temperature versions use a different thermistor,
which must be read using an ohmmeter.)
To read temperatures using an ohmmeter:
1) Connect an ohmmeter to the green and white thermistor leads coming from the instrument.
Since the resistance changes with temperature are large, the effect of cable resistance is
usually insignificant. For long cables a correction can be applied, equal to approximately
14.7 Ω per one thousand feet (48.5Ω per km). Multiply this factor by two to account for both
directions.
2) Look up the temperature for the measured resistance in Appendix B, Table 3.