Trials of a new relative humidity sensor

Abstract

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