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Operating temperature range

The operating temperature range is the ambient temperature range where strain gagescan be used without any permanent changes in their measuring characteristics occur- ring. Depending on whether absolute (with zero point reference) or relative (without zero point reference) measurements are to be carried out, there are different operating tem- perature ranges.

Temperature response in a 1/4-bridge circuit

Strain gages that are connected individually show an output signal, if the temperature changes. This signal is called apparent strain or thermal output and is independent of the mechanical load on the test object.However, it is possible to adjust a strain gage to the thermal expansion coefficient of aspecic material such that the output signal in case of a temperature change is very small. These strain gages are called strain gages with matched temperature response or self-compensated strain gages. All HBM strain gages, with the exception of the LD20 high-strain gage, are self-compensated.To benet from their matching to the temperature response, strain gages must be selected according to the thermal expansion coefficient α of the test object. Therefore,HBM offers strain gages for different materials. The code number for the temperature response matching is included in the type name of the strain gage. Thus, for example, the types LY 21 or RY 31 (code number 1) have been matched to ferri-tic steel with 1for ferritic steelwith α =10.8 10
-6 /K 3for aluminumwith α = 10.8 10-6/K). The material to which the respective strain gage hasbeen adjusted is specied on the package. The remaining temperature variation is printedon the package in the form of a diagram and a polynomial. The effects of strain gages using connection leads are also taken into account thus enab- ling the apparent strain to be compensated by wiring or mathematically. α =23 10
-6 /K 5for austenitic steelwith α =16 10
-6 /K 6for quartzwith α =0.5 10
-6 /K 7for titanium/gray cast ironwith α =9 10
-6 /K 8for plastic materialwith α =65 10
-6 /K9for molybdenumwith α =5.4 10
-6 /K Strain Gages and Accessories15