Comparison and calibration of four instruments for the measurement of electric potential at the surface of non-planar bodies

Abstract

– The electric potential measurements carried out to assess the presence of electric charges at the surface of a body are affected by the geometry of the probe-target system. The present work was specifically aimed at formulating recommendations for the calibration of two non-contact voltmeters and two field-meters currently employed for monitoring the electric potential at the surface of non-planar bodies. The experiments involved the measurement of the electric potential at the surface of planar and cylindrical electrodes of various shapes and sizes, connected to a positive high-voltage supply of 1.5 kV. The readings of each instrument were analyzed in relation with the configuration of the electrodes. As the four instruments have been designed for monitoring the electric potential on relatively large planar surfaces (>100 cm²), specific calibration was needed for measurements on bodies having geometrical characteristics that differ from those specified by the manufacturers. The experiments have shown that the interpretation of the results should consider the fact that the accuracy of the measurements diminishes when the axis of the probe approaches the edges of the electrode. In the case of non-planar surfaces, the measured values should be corrected by coefficients that can be determined by experiments conducted in conditions that mimic the situations of practical interest.