Circuit arrangement for measuring the root mean square value or of the square of the root mean square value of a voltage.

摘要

1,167,331. Measuring voltage. SOLARTRON ELECTRONIC GROUP Ltd. Jan. 11, 1967 [Jan. 18, 1966], No.2377/66. Heading G1U. [Also in Division H3] In a voltmeter for producing a D.C. output proportional to the mean square or r.m.s. value of an intput voltage, the intput voltage is sampled at discrete times at a mean frequency f, a series of unidirectional pulses are formed each of height proportional to a voltage sample, the pulses are integrated to give a D.C. output and this output is also sampled at a mean frequency f, the output voltage samples being fed back to the input of the integrating stage so that the integrated output is independent of the sampling frequency f. The output of a sampler 11, triangulater 12 and rectifier 25 (See Division H3) is a train of pulses 32 of mean area proportional to the mean square value of a voltage Vi being measured and to the frequency f of sampling, this being varied during the measurement to ensure that it is not equal to the frequency of the voltage Vi. The output of the rectifier is fed to a function generator 33 and integrating amplifier 34, the function generator being of the kind described in Specification 1, 050, 145. A negative feedback voltage is taken from the output Vo, which is measured in a D.C. voltmeter, to the input of the function generator through a second sampler 36 operating at the frequency f and triangulater 37. The shape of the hypotenuses of the output pulses of the triangulaters can be made proportional to Vo by feeding back a signal from the output to constant current generators, Fig. 1 (not shown) in the triangulaters. In a modification, Fig.4 (not shown) the rectifier 25 is replaced by a pulse generator, a transformer and a ramp generator. The pulse generator forms a train of rectangular pulses where time spacing is proportional to the input voltage samples, and these pulses are fed through the transformer to the ramp generator which forms a train of unidirectional triangular pulses 48, Fig.4 (not shown) similar to 32 but with the hypotenuses leading the verticals.