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3.3. Measuring Temperatures
Each Vibrating Wire Embedment Jointmeter is equipped with a thermistor for reading
temperature. The thermistor gives a varying resistance output as the temperature changes.
Usually the white and green leads are connected to the internal thermistor.
1. Connect an ohmmeter to the two thermistor leads coming from the jointmeter. (Since the
resistance changes with temperature are so large, the effect of cable resistance is usually
insignificant.)
2. Look up the temperature for the measured resistance in Table B-1 (Appendix B).
Alternately the temperature could be calculated using Equation B-1 (Appendix B). For
example, a resistance of 3400 ohms equivalent to 22° C. When long cables are used the
cable resistance may need to be taken into account. Standard 22 AWG stranded copper
lead cable is approximately 14.7
/1000' or 48.5
/km, multiply by 2 for both directions.
Note: The GK-403 and GK 404 readout boxes will read the thermistor and display
temperature in
C automatically.
