This paper gives technical data on a Wheatstone bridge type of balanced direct current photoelectric amplifier adapted for use on 110‐volt a.c. commercial power lines. The instrument is especially designed for use with the standard recorders employed by the U. S. Weather Bureau, and is to be used in the study of ultraviolet solar radiation and the determintaion of the amount and variation of ozone in the stratosphere. Performance tests indicate that the instrument is equivalent to the older battery type in sensitivity and precision. It is, furthermore, free from the disadvantages of requiring constant voltage adjustments, sensitivity tests, and the constant attention of an experienced operator.