Development of Precise Low Value Capacitance Measurement System for Cryogenics Two Phase Flow Application

In cryogenic two phase flow, it is always challenging to measure the quality and void fraction. In this regard, an effort has been made to indigenously develop an electronic circuit to measure the void fraction by measuring the capacitance of the order of picofarads accurately depending upon the dielectric constant of nitrogen in vapor and liquid phase. The state-of-art electronics card has been developed and tested successfully for its performance and validation. Using this card, an experiment has been conducted using liquid nitrogen cryo transfer line to study the two phase void fraction. In this paper, the design basis and working principle of the designed electronics card along with the performance results are discussed. A/D conversion and DAQ system has been implemented to display the direct measurement data in a computer.