The effects of asymmetry on capacitive angular sensors

Ratiometric measurement schemes are widely used where sensors can be segmented so that the quantity of interest can be determined from the relative differences of the signals captured at each segment. This idea relies on the basic assumptions that the individual segments are measured simultaneously and that these signals obey certain symmetry rules with respect to the quantity to be measured. Unfortunately, both assumptions cannot fully be met in practice. This paper investigates the influence of asymmetry on a segmented capacitive angular sensor. Particular emphasis is placed on the noise introduced by a sequential rather than simultaneous measurement of the segments and by asymmetries due to the sensor geometry and fabrication tolerances. We find the measurement algorithm to be relatively robust provided that only one type of asymmetry dominates.