Dynamic rms converter

Claim 1

A signal measuring device which provides an output direct current voltage which is proportional to the root-mean-square (RMS) value of an alternating input signal applied to the device, comprising: an input terminal for receiving the alternating input signal; rectifier means including halving means, the rectifier means having input means connected to receive the alternating input signal and providing to input means of said halving means a first current proportional to the magnitude of the alternating input signal traversing in a first direction or a second current proportional to the magnitude of the alternating input signal traversing in a second direction, said halving means having at least two output means and providing at one of said at least two output means a third current whose absolute magnitude is half of said first or second current magnitude and providing at the other of said at least two output means a fourth current whose absolute magnitude is half of said first or second currents, the said third and fourth currents having equal absolute magnitudes; function means having input means, control means and output means, the input means connected to receive the third and fourth currents and the function means providing at its output a fifth current which is the product of the third current, the fourth current and the inverse of an additional current received by the control means; and averaging filter means having input means and output means, the input means connected to receive said fifth current and the averaging filter means providing at its output said additional current, the additional current flowing through a resistance means to provide the direct current voltage proportional to the root-mean-square value of the alternating input signal applied to the device.