Calibration history of some Rotronic MP-100 and Vaisala Humicap relative humidity sensors

Abstract

An analysis has been made of the calibrations done during 1990 through 1994 on Rotronic MP- 100 relative humidity sensors (used in the Improved METeorological (IMET) system and sensors built at the Woods Hole Oceanographic Institution (WHOI) with the Vaisala Humicap sensing element (used in the Vector Averaging Wind Recorder (VAWR)). The shift from one calibration to the next is, typically, 2-3% RH which represents the major uncertainty in relative humidity with either of these sensors. The direction of each shift appears to be random; thus, there does not appear to be any long-term drifts.