A novel technique on MZI based electro-optic type pressure transmitter using modified bourdon tube

Abstract

Bourdon tube, an indicating type pressure measuring instrument is used as a local indicator and display unit. Hence a special technique is needed to transmit and to display the reading of a bourdon gauge at remote location. In this paper, a modified bourdon tube has been proposed which is capable to transmit the measured pressure information via optical domain by employing the method of electro-optic effect in Mach–Zehnder interferometers (MZI). Modification in the bourdon tube is done by fabricating an inductor coil to the arm of the bourdon tube. The movement of the bourdon tube is measured in terms of the voltage drop across the inductor. Voltage drop measured by digital voltmeter, across the inductor coil linearly increases (2.29V–2.38V) as pressure increases (0PSI–40PSI). Amplification of the voltage drop across the inductor coil is done by instrumentation amplifier and the Optical transmission is done by the electro-optic modulation with the help of the MZI. The voltage required for electro-optic modulation is achieved by the signal conditioning circuit which is connected with the instrumentation amplifier. It has been observed that the variation in the pressure is directly proportional to the intensity modulated light signal which has very good linearity and repeatability. The required theoretical equations along with the experimental results are reported and compared in this paper.