A Novel Approach to Hydrogen Sensing

A novel sensor for the selective detection of hydrogen in the presence of other reducing gases is presented. The device comprises a commercially available non- or partially-selective semiconductor gas sensor and an air filled centimeter-long capillary tube. The attachment is so that upon exposure, the target gas diffuses in air through the length of the capillary before affecting the sensor. The hydrogen component of the gas mixture diffuses much faster than other components, and is sensed at an earlier stage of the sensor response. The response of a capillary-attached gas sensor (CGS) to a gas mixture containing hydrogen is mathematically analyzed. The results indicate that the hydrogen concentration can readily be extracted from certain mathematical features of the transient response. The fabrication of a prototype CGS and experimental verification of the analytical results are reported. The prototype can measure hydrogen concentration at the presence of other reducing and combustible gases exceeding its concentration by two orders of magnitude.