Measurement of gas moisture in the PPM range using porous silicon and porous alumina sensors

This paper reports the performance of a porous silicon (PS) sensor for detecting ppm level moisture and compares its relative performance with that of porous alumina (PA) sensors. The porous alumina sensor is fabricated by the sol-gel technique. It is found experimentally that in measuring ppm level moisture the sensitivity of the PA sensor appears to be greater than that of the PS sensor while the response time of the PS sensor is much shorter than that of the PA sensor. A simple but precise technique for the electronic measurement of sensor capacitance, which minimizes the parasitic earth capacitances, has been developed to study the response of both PS and PA gas moisture sensors. The detection electronics can be utilized for an integrated sensor unit. However, initial characterizations of both PS/PA sensors are carried out using a standard LCR meter (HP-4284A) to establish the electronic circuit.