A Four Terminal Pair Digitally Assisted Impedance Bridge at TUBITAK UME

Capacitance and AC resistance comparisons at audio frequencies are being performed by using a four-terminal pair transformer- based coaxial AC bridge at TUBITAK UME. A four-terminal pair digitally assisted (DA) coaxial AC bridge has been developed in order to reduce the complexity of coaxial transformer AC bridges. This paper describes realization of fourterminal pair DA coaxial AC bridge using commercial DAQ modules and performance test measurements by using the transformer-based bridge. According to preliminary results, the bridge can be balanced automatically in less than 5 minutes. R- R and C-C comparisons at 1 kHz and 10 k Omega magnitude level give ratio errors of a few 10(-6). Further improvements for ratio errors and bridge balancing time will be performed.