Design of a new thick film capacitive pressure and circuitry interface

In recent years, number of studies investigating the use of capacitance effects in mechanical transducers has been undertaken. It was found that changing the dimensions of the chemical constitution of the dielectric material could change the nominal value of the parallel plate. This fact has been used to develop sensors that measure quantities such as strain, acceleration, gas concentration, humidity, etc. [1]. This paper is focused on developing a low-cost pressure sensitive device using thick film technology. The paper illustrates the original design specifications and how the sensor and signal conditioning circuitry performed against expectations. One of the design constrains was ensuring the operation of the sensor in a hostile operating conditions. Several device configurations were made based on both commercial Cermet and a PZT pastes. The relative performance of these materials as a dielectric-sensing element is compared in terms of their sensitivity, repeatability, and hysteresis. An efficient signal conditioning circuitry has been developed. The purpose of the circuitry is to allow the interface to make control decisions based on accurate stable pressure readings obtained by at the circuit. In this paper, the full system design of the pressure sensor and compensation circuitry was considered.