Heat-sink properties of the mounting surface. Also, the shape of the gaged part may create thermal stresses in portions of the structure due to gage self-heating. Long warm-up times and apparent gage instability can result. The situation often arises in low-force transducers, where thin sections and intricate machining are fairly common. Strain measurement on plastic requires special consideration.
Most plastics act as thermal insulators rather than heat sinks.
Extremely low values of excitation are required to avoid serious self-heating effects. The modulus of elasticity of the common plastics drops rapidly as temperature rises, increasing visco-elastic effects. This can significantly affect the material properties in the area under the strain gage. Plastics which are heavily loaded with inorganic fillers in powder or fibrous form present a lesser problem, because such fillers reduce expansion coefficients, increase the elastic modulus, and improve thermal conductivity. Environmental operating temperature range of the gage installation.