The "Strain-Gauge Thermocouple": A novel device for simultaneous strain and temperature measurement

A novel methodology for simultaneous strain and temperature measurements by means of an ac powered electrical resistance strain gauge connected to a strain conditioner using thermocouple wires is proposed and validated. To this aim a specific device has been designed and implemented; the characteristics of the electronic circuit for signal conditioning have then been tested in order to determine the overall performances in temperature and strain measurements. The field verification of the method is conducted by imposing strain fields in the range from 0 to about 700 mum/m and temperature variations in the range from -10 to 100 degreesC. The difference between the strain measured by the proposed device and the one evaluated by a conventional digital strain meter was always less than 4 mum/m while the mean temperature discrepancy was 0.5 degreesC with respect to the reference temperature measured with a K-type thermocouple. Finally, compensation of temperature effects on the actual strain value has been performed while the temperature ranges from ambient to 100 degreesC with a residual error value of 1.4 +/-1 mum/m. (C) 2001 American Institute of Physics.