Trials of a new relative humidity sensor

Abstract

A new relative humidity and air temperature sensor, the Sensirion Model SHTl, has been thoroughly tested \nby the Upper Ocean Processes (UOP) group at the Woods Hole Oceanographic Institution. One-minute \naverages from two of the sensors, as well as a Väisälä HMP4SA, were recorded for over a year. A third \nSensirion sensor was kept in the laboratory and calibrated at monthly intervals with the other three sensors. \nThe standard deviation of the difference in relative humidity between the Sensirion sensors and the Väisälä \nwas about 2% RH. The difference in air temperature was about 0.2°C. Drift rates in relative humidity for the \ntwo Sensirion sensors were 2.7% RH/yr and -0.3% RH/yr, and in air temperature, O.1°C/yr and 0/3°C/yr. \nBecause one of the two Sensirion sensors deployed outside had significant variations in its calibration, the \nUOP group will not adopt these sensors. However, their very small size, low-cost, and low-power \nrequirements may make them desirable for other uses.