On the zero offset stability of thick film strain gauges

Abstract

This paper presents results of work aimed at characterising the zero offset stability in novel thick film strain gauges. The devices studied are z‐axis (k33) load sensors fabricated on insulated stainless steel substrates and include examples of novel commercially developed force sensors. Devices loaded with compressive strains using a purpose designed test jig were found to exhibit a significant zero offset shift, which is negative up to a certain level (typically 1,000 micro strains) and then increasingly positive when strained beyond this point. Repeated cycles of loading then produced a certain level of stability until the previous maximum value of applied strain was exceeded. Temperature coefficient of resistance (TCR) measurements showed the devices to exhibit characteristics that depend significantly on the device geometry. The TCR was found to increase positively with increasing device thickness and surface area. The effect of overglazing the devices was found to decrease the TCR.

LTCC Post Load Cell

“…A design of a z-axis piezoresistive force sensor, using the geometry shown in Figure 1b, was previously introduced to obtain high levels of strain [11,12].…”

An explanation of thermal behaviour of thick film strain gauges

“…However it is reasonable to think that the results derived from this model are valid to show the trend in the case with ceramic substrates as well. The dimensions employed in the modelling were those typically adopted in most of the test work [5,7,8], especially with the K 33 devices described in the following section. Uniform temperature variation from 20˚C to 130˚C is the only load which is applied to the model.…”