Measurement Geometry
Error mechanism occurring in proximity sensors where non-parallel alignment between the probe face and the target surface alters the electric field. In an ideal setup, capacitive gap distortion is absent when the sensor and target remain perfectly parallel. Any angular deviation introduces a gradient in the gap distance across the sensing area.
The shift in effective capacitance value deviates from the theoretical calculation for a uniform plane.
Error Source
Tilt and curvature of the target material represent the primary physical drivers of inaccurate readings. When the target surface is not flat, capacitive gap distortion arises from the non-linear relationship between distance and capacitance. Sensors with larger diameters experience more pronounced effects from surface irregularities than smaller probes.
The resulting measurement bias often exceeds the stated linearity specification of the instrument.
Calibration Correction
Guarding techniques and active compensation algorithms help mitigate the impact of misalignment. By surrounding the sensing electrode with a guard ring at the same potential, manufacturers reduce the fringing fields that exacerbate capacitive gap distortion. Software based linearization can also account for known tilt angles if the orientation is fixed.
High precision applications require mechanical adjustment stages to null out the angular error before data collection. Proper grounding of the sensor housing reduces parasitic capacitance that can mask the signal. Technicians verify the alignment using a series of reference shims during the initial setup.
Environmental Influence
Dielectric changes in the medium between the plates further complicate the sensor output. Humidity and temperature fluctuations alter the permittivity of air, which interacts with capacitive gap distortion to produce unpredictable drift. Cleanliness of the gap is also a factor, as particulate matter or oil films change the local field strength.
Stable operation relies on maintaining a controlled environment or using differential sensor pairs to cancel common mode errors.
