A NOVEL AND ECONOMIC SENSOR SYSTEM FOR MONITORING OF AMMONIA

摘要

Refrigerator systems, heat pumps and air conditioning facilities have to be monitored for coolant leakages to enable alarms and precaution if certain concentration levels are exceeded (pre-alarm: 200vpm, main alarm: 1000vpm). Nowadays metal oxide gas sensors of the tin oxide type are preferably used as sensor elements due to their good sensitivity, long-term functionality and low application costs. In general, however, a still unsolved problem of automatic safety control by monitoring of flammable and hazardous gases in air is the gas identification capability and the reliability of this type of sensor at changing temperature and humidity conditions. In the case of ammonia used as coolant medium we present a novel and economic sensor system which enables both ammonia identification and concentration determination under variing air humidity. This will reduce the risk of false alarms drastically.