Digital instrument for measurement of autocorrelation and moments

The portable digital instrument described provides decimal readouts of the autocorrelation, mean value and measuring time of a voltage under measurement, using three displays. The upper frequency limit is about 2 kHz. The instrument has no low-frequency limitations. Readout is available immediately at the end of a measuring run. 20 values of delay between sample pairs are provided for. If the delay is zero, the autocorrelation value is the mean square of the input voltage. Hence, the instrument provides measurements of first and second moments, as well as autocorrelation. The voltage under measurement is sampled systematically, and the sample pairs are processed as soon as they are available, using a unique, special-purpose, digital computer. The paper describes the principles on which the measurements are based, and the design and error characteristics of an instrument which has been constructed. For many waveforms, the maximum error is well within 1%.