Calibration of rain gauge and thermohygrometers in automated weather stations

Abstract

In Venezuela, farms and research institutes have incorporated Automatic Weather Stations (EMA, acronym in Spanish) in their systems, which require calibration periodically to ensure the reliability of results. The aim of this work was to verify the calibration of a rain gauge PCR800  (Brand Oregon)  and three Thermo hygrometers WMR200A (Brand Oregon) before installation.  Static and dynamic tests were applied in the rain gauge. The Thermo hygrometers THGN801 were calibrated by adjusting the temperature in the oven and the results were compared with a calibrated Thermo hygrometer.  The rain gauge static test indicated that the differences between the added water and water recorded for all levels were not significant (P<0.025); while the dynamic test indicated a maximum difference of 3 mm between wireless rain gauge and conventional one, used as a reference.  Thermo hygrometers differences in temperature and relative humidity with respect to standard did not exceed tolerances of the equipment and showed no significant variations (P<0.025).  It was verified that the calibration of the gauge and the Thermo hygrometers were conformed to the tolerances stated by manufacturers for a wide range of levels of precipitation, temperature, and relative humidity.