Simple devices for radiation measurement and integration

Simple thermopiles formed by copper-plating a constantan wire were used to build a solarimeter and a net radiometer. Output was 5–10 mV per cal·cm−2·min−1, adequate to operate a small portable galvanometer for spot readings, a continuously recording potentiometer, or, for integration, a Siemens electrolytic meter. The net radiometer was unventilated, but when oscillated manually, output was independent of wind speed. With two solarimeters in a null-balance circuit, reflection and transmission coefficients of a field crop were read directly on a dial. A circuit was designed to integrate solarimeter output and the standard error of weekly readings was only ±40 cal·cm−2.