Virtual instrument based instrumentation for harmonic current emission measurement

An instrumentation system for the measurement of harmonic emission to IEC 61000-3-2 is a subset of the general problem of harmonic measurements. A condition is derived for the SNR of a signal (with monotonically decaying harmonic amplitudes) to be zero due to quantization errors. This is enlarged to cover Gaussian noise in the analog front end of the measuring system. A virtual instrument, which can considerably improve the measurement accuracy of a single stage analog front end and digitiser, is then suggested.