Capacitive Proximity Sensor Maximum Range Dependence on Geometry and Size

In this research paper, the method for evaluating detectable range of the capacitive proximity sensor depending on the sensor geometry, surface area, and plate separation distance is presented. In experiments, three shapes were used - square, rectangle, and circle. For each shape, multiple measurements were made, while keeping the surface area and separation distance of the shapes equal. The basis for capacitance measurement was a resonance frequency of the LC circuit with a high-speed comparator to convert AC signal to DC square signal - as a result, it is a capacitance-frequency converter. From measured frequency, the capacitance can be calculated if other parameters (permittivity of dielectric, surface area, separation distance of sensor plates) are known. To gather necessary data the capacitance was also measured with an LCR meter and the permittivity of dielectric material was calculated. As a result of the measurements, the most optimal shape, surface area, and separation distance of sensor plates were selected while keeping detectable distance as the main consideration.