6
Figure 2 GK405 Readout Unit
For further details consult the GK405 Instruction Manual.
3.4. Measuring Temperatures
Each Vibrating Wire Convergence Meter 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.
The GK-403, GK-404 and GK-405 readout boxes will read the thermistor and display
temperature in
°
C automatically.
However, if an ohmmeter is used
1. Connect the ohmmeter to the two thermistor leads coming from the convergence
meter. (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 is 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
Ω
/1000' or 48.5
Ω
/km,
multiply by 2 for both directions.
