The Property Analysis of a Plane Type Capacitance Sensor for Object Detection

Abstract

The authors focused on the applicability of capacitance sensors as a human body detecting/monitoring means to realize high-performance equipment to assist in caring for the aged. As the human body contains a high percentage of water, it has a high specific inductive capacity to be detected, that sets it apart from objects such as plastics. This report describes the positive result obtained by using FEA (Finite Element Analysis) to determine how capacitance is affected by parameters such as the interval between measurement electrodes, the distance from an object, and differences in specific inductive capacity of objects with respect to a pair of square electrodes arranged on a plane. Capacitance was calculated by preparing a 2-dimension model of plane type capacitance sensor utilizing the general-purpose FEA software ANSYS. As a result, it was found that increasing the interval between measurement objects enables them to be detected from a greater distance. This distance is approximately equal to that between electrode centers, and is an important factor for detection limit distance defining the performance of plane type capacitance sensors. Furthermore, this paper shows that the sensor is impervious to intervening material, which may exist between the sensor and object, and that the sensor is capable of detecting the presence of a person, due to the high dielectric constant of the human body.