Evaluation of Measurement Uncertainty for Polymer Thin Film Humidity Sensor Using CMH and PRT Based on Dew Point Temperature Variation

Abstract

The purpose of this paper is to propose appropriate evaluation method of measurement uncertainty with respect to the measurement results of polymer thin film capacitive humidity sensor according to dew point temperature variation. All of the evaluation process concerning the measurement uncertainty of polymer thin film capacitive humidity sensor is based on experiment and numerical analysis. To estimate uncertainty contribution properly for polymer thin film capacitive sensor strongly influenced by measurement environment, the experiments are performed in the reference relative humidity range from 5 % to 30 % at a setting dry bulb temperature of 23°C. Also, the reference standards are chilled mirror hygrometer (CMH) and platinum resistance thermometer (PRT). In particular, the uncertainty sources are considered differently according to the range of below or above 0°C, reference dew point. From the budgets, uncertainty contributions to the standard uncertainty are clearly dominated by the effect of the uncertainty due to super-cooling in case of condition below 0°C, dew point temperature. Also, the contributions for stability and distribution of humidity generator have a mainly effect on the expanded uncertainty of polymeric humidity sensor. It is desired that measurement uncertainties of polymeric humidity sensor are comprised separately on the basis of reference dew point, 0°C. The evaluation procedure of measurement uncertainty is developed in accordance with the principles established in the documents EA-4/02, Expression of the Uncertainty of Measurement in Calibration [1].