An experimental evaluation of duct-mounted relative humidity sensors: Part 3 - Repeatability, hysteresis, and linearity results
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This is the final paper of a three-part series reporting on the test and evaluation of typical duct-mounted relative humidity sensors used in building HVAC applications. In this paper, three duct-mounted humidity sensors from each of six different manufacturers (i.e., models A to F) were tested and evaluated to determine the sensor repeatability, hysteresis, and linearity. The experimental database of the accuracy study, as described in the Part 2 paper (Joshi et al. 2004b), was used to evaluate the repeatability, hysteresis, and linearity of sensors. The results show that at 50% RH, the sensors are repeatable within 1.5% RH for temperatures of 15C, 25C, and 35C. The maximum hysteresis for all sensors is less than 3.2% for all humidities and temperatures. The hysteresis is positive for all temperatures, humidities, and sensor models. For most of the humidity range, Model B has the largest nonlinearity of - 3.8% RH while Model C has the least nonlinearity of 0.0% RH. Finally, the magnitude of the errors in repeatability for all sensor models at 25C and 50% RH is smaller than the magnitudes of both hysteresis and linearity. 2005 ASHRAE.
