Versatile four-probe ac conductivity measurement system

Abstract
The design of a four‐probe ac conductivity measurement system is described. The system is capable of making precision conductance measurements from 10−8 to 10−5 S at 20 to 200 Hz. Driven coaxial shields and a controlled current source are utilized to eliminate phase shift/attenuation errors, and make the measurement of conductances on a variety of materials a routine procedure requiring a minimum of operator intervention.
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