DESIGN, CONSTRUCTION AND TESTING OF A SYSTEM FOR DETECTION OF TOXIC GASES BASED ON PIEZOELECTRIC-CRYSTALS

A system for static operation of toxic gas sensors based on piezoelect ric crystals was constructed as a preliminary step in the development of this type of sensor. The sensing part of the setup consists of a tw in oscillating circuit assembled from commercially available electroni c parts mounted on a motherboard. The oscillating circuits can accommo date two piezoelectric crystals, of which one or both can be coated wi th different materials, or a single one, as required. The sensing asse mbly (crystals plus oscillating circuits) is placed in a customized te st chamber that allows one to control and reproduce its internal envir onment. Once assembled and fine-tuned, the proposed setup was used to test a commercially available piezoelectric crystal for sensing formal dehyde in order to expand available information on this type of sensor .