“Matsumoto”s torsion meter is used mainly for the purpose of measuring shaft horse power equipped on the intermediate shaft of marine engine. We divide, for convenince, this meter into two parts; the detecting part of shaft torsion and indicating part thus detected. This device leaves detecting part as it is, but in indicating part use the special circuit involving “Ring-modulator” circuits. With this device, we can indicate torsion using ordinary voltmeter, without any special one, and by changing resistance in the circuit we can vary its sensibility in broad range without raising primary voltage.