Appendix E.Model 4200HT / 4200HT–T
High-Temperature Strain Gauges
geokon Model 4200HT and 4200HT-T High-Temperature Embedment Strain Gauges are similar to the Model 4200, but are constructed using components that can withstand temperatures up to 200 °C (4200HT) and 220 °C (4200HT-T). They are particularly useful for measurements in autoclaved spun concrete piles.
20:
21:
Figure 21: Model 4200HT-T
Data interpretation is the same as that outlined in Section 7, with the exception of the Temperature Coefficient for the Model 4200HT-T, which is 17.3 με / °C. Coil resistance for Model 4200HT is 120 ohms, and is 50 ohms for the 4200HT-T.
The thermistor included with the gauge is a high-temperature thermistor, which uses the resistance to temperature conversion table shown in Table 7. When using a readout box, it is not necessary to connect the green and white wires to the readout because the temperature shown on the readout will be incorrect. Instead, use a digital ohmmeter.
To read temperatures using an ohmmeter
1.Connect an ohmmeter to the green and white thermistor leads coming from the strain gauge. (Since the resistance changes with temperature are large, the effect of cable resistance is usually insignificant.)
2.Look up the temperature for the measured resistance in Table 7.