Thermo-galvanometer

—A_ pair of instruments devised by Duddell for measuring the current delivered by a high frequency alternator. They are capable of registering through a very great range from `a micro-ampere to many amperes. The operating principle is that the heat generated by the current in a wire acts upon a thermo-electric junction which forms a part of a galvanometer circuit. This device may be used as a detector in wirele telegraphy over considerable distances.