Mean square transducer

Claim 2

In combination: a. multiplying means having input and output terminals for producing at its output terminals a voltage which is a measure of the square of an alternating current supplied to its input terminals; b. an input circuit adapted to be energized by an alternating voltage of variable RMS value, said circuit including resistance of variable ohmic value and being arranged to supply to the input terminals of said multiplying means a current proportional to the ratio of said RMS value to said ohmic value; c. comparison means for deriving an error signal which varies with the difference between the average magnitude of the voltage at said output terminals and a predetermined constant reference level; d. control means actuated by said error signal for varying the ohmic value of said resistance as necessary to reduce said error signal to zero; and e. readout means responsive to said ohmic value for producing an indicating signal which varies therewith, whereby said indicating signal is a measure of said RMS value, said readout means including output resistance, means coupled to the resistance of said input circuit and operative in response to variations in said ohmic value for correspondingly changing the ohmic value of said output resistance, and means connected to said output resistance for producing a DC output voltage whose magnitude varies with the ohmic value of said oUtput resistance.

Claim 3

Apparatus as in claim 1 wherein said multiplying means is a Hall device.

Claim 4

The combination of claim 1 wherein said means connected to said output resistance comprises an amplifier having a DC input voltage of fixed magnitude and having a variable gain which depends on the ohmic value of said output resistance.

Claim 5

Apparatus as in claim 3 including a readout voltmeter and wherein said voltage of said amplifier drives said readout voltmeter.

Claim 6

In combination: a. an input circuit adapted to be energized by an alternating voltage of variable RMS value, said circuit being operative to provide an AC signal whose RMS value is proportional to that of said alternating voltage and including resistance of variable ohmic value which determines the proportionality therebetween; b. means connected to said input circuit and responsive to said AC signal for deriving an error signal which varies with the difference between the average magnitude of the square of said AC signal and a predetermined DC reference level; c. control means comprising a servo system coupled to the resistance in said input circuit and excited by said error signal for causing adjustment of the ohmic value of said resistance as a function of said error signal so as to vary said proportionality as necessary to reduce said error signal to zero; and d. readout means for producing an indicating signal which varies with said proportionality, whereby said indicating signal is a measure of said RMS value, said readout means comprising i. output resistance, ii. means coupled to the resistance in said input circuit and operative in response to variations in said ohmic value for correspondingly changing the ohmic value of said output resistance, and iii. means connected to said output resistance for producing a DC output voltage whose magnitude varies with the ohmic value of said output resistance.

Claim 7

In combination: a. an input circuit adapted to be energized by an alternating voltage of variable RMS value, said circuit being operative to provide an AC signal whose RMS value is proportional to that of said alternating voltage and including resistance of variable ohmic value which determines the proportionality therebetween; b. means connected to said input circuit and responsive to said AC signal for deriving an error signal which varies with the difference between the average magnitude of the square of said AC signal and a predetermined DC reference level; c. control means comprising a servo system coupled to the resistance in said input circuit and excited by said error signal for causing adjustment of the ohmic value of said resistance as a function of said error signal so as to vary said proportionality as necessary to reduce said error signal to zero; and d. readout means for producing an indicating signal which varies with said proportionality, whereby said indicating signal is a measure of said RMS value, said readout means comprising i. output resistance, ii. means coupled to the resistance in said input circuit and operative in response to variations in said ohmic value for correspondingly changing the ohmic value of said output resistance, and iii. means connected to said output resistance for producing a DC output voltage whose magnitude varies with the ohmic value of said output resistance.

Claim 8

The combination of claim 5 in which said error signal deriving means comprises a Hall device having output terminals at which is produced a voltage which is a measure of the square of said AC signal and comparison means for deriving said error signal from the difference between the average magnitude of the voltage at said output terminals and said predetermined reference level.