AN APPLICATION FOR THE CALIBRATION OF THE TWO-PRESSURE HUMIDITY GENERATOR

Abstract

Two-pressure humidity generator (2-PHG) has capability to produce environments of known humidity with the “two pressure” method that is proven by NIST. The 2-PHG is supplied with known humidity values, the values can be used for instrument calibration, verification and such as other processes. The set point values can be entered from the device’s front panel by an operator. 2-PHG calculates the relative humidity from the pressure and temperature measurements with the formula. The computer controls the ratios on the formula to generate a known humidity value. 2-PHG has to have traceability for using on calibration processes of other devices; 2-PHG must be calibrated. This study represents an application of the 2-PHG calibration by using the guides and articles in the literature about the device. Calibration of the 2-PHG contains examination of the each parameter of the formula that was given for humidity calculation. Four temperature and two pressure probes that are saturation temperature probe, pre-saturation temperature probe, expansion valve temperature probe, chamber temperature probe, low pressure probe, high pressure probe help 2-PHG to calculate the formula. Calibration of the 2-PHG, also, contains the calibration of the temperature probes and the pressure probes. This study expresses an application of the calibration of a 2-PHG which is located in Turkish Standard Institution Gebze Calibration Laboratories and the uncertainty calculation of this application can be seen on this paper. Each uncertainty parameter of the formula and uncertainty parameters of the probes that are affected to the total uncertainty were calculated. For different temperatures and different relative humidities, the measurement uncertainty of this application was given on this paper. This study can be used as a supplementary document in the calibrations of the 2-PGH and in the new studies.