A Thermistor Leaf Thermometer

Abstract

An instrument is described which allows measurements of leaf temperature within about 0.3 C. It consists of a special thermistor probe, a small circuit box, and a standard am-meter. The circuit box can easily be fixed to the meter and contains a battery, which passes 0.3 milliampere through the thermistor, and also contains an integrated circuit amplifier, so that the meter reads 20 C full scale deflection, with ranges adjustable in 10 C steps. Calibration experiments show the superiority of the thermistor leaf thermometer to a thermocouple pressed onto a rubber surface with a resilience resembling that of a leaf.