A Portable Thermistor Bridge for Micro-meteorology Among Growing Crops

Using thermistors, a portable unit has been built to measure temperature humidity and wind speed among growing potato crops in connexion with an investigation into factors affecting the spread of virus disease. Type F thermistors are used as resistance thermometers for measuring dry- and wet-bulb temperatures: Type L, with the glass sheath removed, is used to measure wind speed on the hot-wire anemometer principle. For the latter, the response has been found to depend upon ambient air temperature, but by including another thermistor in the bridge circuit complete compensation has been achieved over a temperature range from 13° to 30° C.