A Temperature Compensated Non-Contact Pressure Transducer Using Hall Sensor and Bourdon Tube

Abstract

This paper describes the design of a simple non-contact-type pressure transducer using a Bourdon tube and a Hall sensor where the effect of atmospheric temperature is compensated. In this design, a pressure sensing Hall IC is fixed with the nonmagnetic aluminum casing of a Bourdon gauge in front of a tiny disc-type permanent magnet rigidly attached with the free tip of the Bourdon tube. With the increase of pressure of the fluid inside the Bourdon tube, the free end along with the magnet moves toward the Hall sensor, and the magnetic field intensity due to the magnet on the Hall sensor increases with an increase of pressure. Due to this magnetic field, the outputs of the Hall sensor and the transducer circuit consisting of a differential amplifier and an instrumentation amplifier increase with the increase of pressure of the fluid inside the Bourdon tube. The transducer circuit consists of a unity gain differential amplifier circuit where the output of a second identical temperature sensing Hall IC is subtracted from the pressure sensing Hall IC output in order to compensate the effect of ambient temperature in the proposed transducer. The theoretical equations describing the operation of the transducer are derived in this paper. The static characteristic curves of a prototype design of the transducer are determined experimentally. The experimental results are reported in this paper. The characteristics curves are found to follow the theoretical equations with good repeatability and are free from ambient temperature effect.