Nonrandom quantization errors in timebases

Timebase distortion causes nonlinear distortion of waveforms measured by sa mpling instruments. When such instruments are used to measure the rms ampli tude of the sampled waveforms, such distortions result in errors in the mea sured root-mean squared (rms) values. This paper looks at the nature of the errors that result from nonrandom quantization errors in an instrument's t imebase circuit. Simulations and measurements on a sampling voltmeter show that the errors in measured rms amplitude have a nonnormal probability dist ribution, such that the probability of large errors is much greater than wo uld be expected from the usual quantization noise model. A novel timebase c ompensation method is proposed which makes the measured rms errors normally distributed and reduces their standard deviation by a factor of 25. This c ompensation method was applied to a sampling voltmeter and the improved acc uracy was realized.