Novel technique for r.m.s.--d.c. conversion based on the difference of squares

A new technique is described for producing a d.c. output proportional to the r.m.s. value of an input having arbitrary waveshape. Like the fundamental method based on a thermal balance, this technique does not require the use of accurate scaling within the nonlinear element; scaling is primarily determined by the ratio of two equal resistors operating at low power.