A sensitive differential wattmeter
L. M. Clarebrough, Mark Hargreaves, D. Michell, G. W. West · Journal of Scientific Instruments · 1953
An instrument for the direct measurement of small differences between the electrical power supplied to two circuits is described. It consists of two similar dynamometer wattmeter elements acting in opposition on the same suspension so that the deflexion of this suspension is proportional to the difference between the power supplied to the two elements.