Presentation on theme: "CORRECTING RMS VALUE OF A SINE WAVEFORM SAMPLED DUE LIMITED NUMBER OF PERIODS AND DETERMINATE APERTURE TIME ON DMM Keywords: Digital Multimeter (DMM),"— Presentation transcript:
CORRECTING RMS VALUE OF A SINE WAVEFORM SAMPLED DUE LIMITED NUMBER OF PERIODS AND DETERMINATE APERTURE TIME ON DMM Keywords: Digital Multimeter (DMM), Root Mean Square (RMS) Error, Sampling, Aperture Time, Number of Samples
NOMENCLATURE DC = direct current AC = alternating current A/D = analog-to-digital RMS = root-mean-square t a = aperture time t 0 = initial phase t a [T] = aperture time in percentage of a period F = frequency F s = sampling frequency n = number of samples ppm = part per million
ROOT MEAN SQUARE Sine waveform segments can be generated according to the following equation: y[i] = A· sin(t 0 [T] + F·360.0· i/F s ), for i = 0, 1, 2, …, n – 1. Sampling info: #s = t a [T]·NRDGS, F s = F·NRDGS. Initial phase can vary. From collected mean values, LabVIEW and Swerlein algorithm (implemented in DMM 3458A instruments) calculates RMS value of a signal waveform. The standard uncertainty associated with the RMS estimate depends on the waveform stability, harmonic content, and noise variance, was evaluated to be less than 5·10 -6 in the 1 - 1000 V and 1 - 100 Hz ranges.