In situ calibration of stress chips

A special test chip having several silicon diffused piezoresistive strain gauges is described that was used to demonstrate an in situ calibration procedure for the gauges. It is based on the use of a high-sensitivity strain measuring technique called Moire interferometry to monitor mechanical strains at the location where the gauges are, thus providing a direct correlation between measured resistance changes of the gauges and actual strains. Many of the limitations and drawbacks of previous calibration techniques have been eliminated by this approach which is direct, simple, and reliable. It is applicable to new as well as existing stress chips