Assessment of ammonia sensors and photoacoustic measurement systems using a gas calibration unit

Abstract

• Study shows measurement techniques for extensive tests of gas measuring devices. • We focused on suitability of devices for measuring ammonia at different humidities. • Photoacoustic gas analysers and electrochemical gas sensors were testet. • With a gas calibration unit, accuracy, response time and drift behavior can be tested. • Pre-testing at laboratory level is crucial to assess the suitability for field trials. The accurate measurement of environmentally-relevant gases such as ammonia (NH 3 ) is increasingly important, especially in agricultural science. Accurate and continuous measurement of gases is essential for evaluating NH 3 and other gases as resource-based indicators of air quality in forced ventilation barns and for determining emission rates. To better assess measuring devices under different barn conditions (e.g. relative humidity or concentration range) self-conducted tests should be implemented at the laboratory scale before, during and after (experimental) measurements in the barn, independent of the manufacturer's specifications. Therefore, in this study, a gas calibration unit was set up for measurements at the laboratory scale. Moreover, measurement protocols were developed to investigate the accuracy at different gas concentrations and relative humidity levels and the responsiveness to rapid gas concentration changes. Measurements were performed with photoacoustic gas analysers (INNOVA 1412) and transmitters with electrochemical gas sensors (Polytron 8100 and C300). In addition to the presentation of results of the devices used in this case, this study should above all offer suggestions for quality monitoring to test sensors more intensively at the laboratory scale in order to be able to use them in a more targeted manner according to their optimal suitability.