Thick-film strain gauges on alumina, zirconia and steel substrates

Strain gauges can be realised by printing and firing thick-film resistors on ceramic substrates that are usually based on alumina. However, sensing elements made on some other substrates - tetragonal zirconia or stainless steel - would exhibit some improved characteristics, either due to a lower modulus of elasticity or a higher mechanical strength. As thick-film resistors are developed for firing on alumina substrates their compatibility and possible interactions with other kinds of substrates have to be evaluated. The sheet resistivities and noise indices of the resistors were comparable, whereas the gauge factors were lower for the dielectric-on-steel substrates. The temperature coefficients of resistivity (TCR) of the resistors on the ZrO2 and dielectric-on-steel substrates were higher than the TCRs on the alumina substrates, which was attributed to the higher thermal expansion coefficient of the tetragonal zirconia and the stainless steel.