Investigations into the measurement sensitivity distribution of coplanar capacitive imaging probes

In this paper, the measurement sensitivity distributions of coplanar capacitive imaging probes are studied. An equation to calculate measurement sensitivity distribution of a coplanar capacitive sensor was derived. The measurement sensitivity distribution of a coplanar capacitive imaging (CI) probe with two back-to-back triangular electrodes was obtained both from finite element (FE) models and experiment. The effects of specimen under test on the measurement sensitivity distribution were discussed. The measurement sensitivity distribution is useful to evaluate the imaging ability of coplanar capacitive probes with different design parameters and to retrieve the actual shape of the targeted feature. The concept of negative sensitivity has also been introduced, and experiments were also performed so as to verify the existence of negative sensitivity.