Conductivity Measurement System Analysis

Knowledge and experimental determination of ac-curate volume resistivity and conductivity is of high importance. Concentrating on measurement arrangements utilizing high voltage supplies, in most cases additional protection units are implemented in order to protect measurement equipment in case of test specimen failure. For this purpose, realization concepts of protection circuits are presented and analysed. Furthermore, requirements and design recommendations for a suitable reduction of capacitive charging currents are derived. Influences on the overall conductivity measurement system behaviour are presented based on analytical system transfer functions. As a consequence, presented mathematical models provide general applicable methods for the design and analysis of conductivity measurement systems. Moreover, effects of the arising field distortion within a guarded measurement arrangement caused by potential imbalances between guarded and guard electrode are broached. This potential imbalance is related to an occurring voltage caused by a voltage drop across the impedance of the protection unit or additional filters prior to current measurement.