Measurement of effective value of voltage in successive intervals - squaring integrating and extraction of square root

An instrument, especially for the study of the starting effects in an electric locomotive, is used for continuous measurement of the effective value of a voltage in successive, interval-less integration times which can be selected to be one or more periods of one of a number of frequencies in a mixture of frequencies. The instantaneous value of an applied voltage is squared in an analogue multiplier and the squared values are fed to an integrator and reduced by the value of the previous integration time before integration over a second period. The resulting value is fed to a sample and hold unit of the integrator and in the next integration period is divided by the integration time in a divider after w hich the root is extracted in a unit so that the output signal at the output represents the effective mean voltage over the integration period.