An energy partition evaporation recorder

A description is given of an instrument which provides a near-continuous measurement of evaporation from natural surfaces. This instrument employs a resistive bridge technique to sense net radiation, ambient wet-bulb temperature and dry- and wet-bulb temperature differences, and employs a servobalance system to combine the corresponding electrical signals according to a modified version of the energy balance formula. Details are given of the instrument's construction, calibration, field operation and performance.