US Patent 7340956 - Built-in self test of MEMS

http://www.freepatentsonline.com/7340956.html

A variety of self-testing methods and systems exist for MEMS sensors including piezoresistive and capacitive diagnostic elements built into the MEMS structure. This patent from Carnegie Mellon teaches using dual sensing elements for generating a differential signal to detect asymmetries of the MEMS sensor. Claim 1 reads:

1. A method, comprising: actuating a MEMS device; and comparing outputs from a first and a second sensor electrically isolated from one another and positioned to produce signals of substantially identical characteristics so as to identify asymmetries in said MEMS device.