By Dataforth Corp.BRIDGE CIRCUITS have been in use for well over 150 years. The original bridge circuit topology has had many unique modifications and has been applied to applications such as AC measurements, automatic balancing, oscillators, and amplifiers. Perhaps the best known application for Samuel Hunter Christie’s circuit is the bridge strain gage for strain type measurements in mechanical assemblies andbuilding structures.Analysis of all the many bridge topologies that compensate for small second order effects are beyond the scope of this application note. Readers interested in the in-depth details of complex bridge topologies and strain gage applications should explore the Internet, which contains thousands of sites dedicated to such details.