Design and development of a capacitance-based wireless pressure transmitter

摘要

A novel, cost- effective and efficient wireless pressure measurement system is modeled for transmission of the signal in harsh environment. The sensing part involves rubber bellows with a capacitive sensor made of copper plates. For remote transmission, monitoring and controlling the mechanical displacement of the bellows is converted into dc output voltage using differentiator and precision half wave rectifier. A linearization circuit is also designed, which linearized the output voltage with a value of percentage deviation from linearity of ±1.8%. For further FSK mode of transmission, the obtained linearized voltage is converted into 1 to 5 volt with a signal conditioning circuit. The transmitted output voltage is recovered using FSK demodulator circuit, LPF and a Decision circuit at receiving end. The full scale percentage error of the measurement system lies within 5% which is in an acceptable range. The proposed method is an economic and efficient transmission technique in hazardous areas where wired transmission is not feasible. The mathematical equations explaining the functioning of the proposed transmitter have been derived. The operation of the proposed pressure transmitter has been experimentally tested. The design approach, mathematical analysis and experimental results of the proposed model are reported in this paper.