AC & DC Estimator VI

Owning Palette: Signal Operation VIs

Requires: Full Development System

Estimates the AC and DC levels of the input Signal.

This VI performs spectral analysis by separating DC (bin 0) from AC (the rms sum of the rest of the bins).

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	Signal specifies the input time-domain signal, usually in volts. The time-domain record must contain at least three cycles of the signal for a valid estimate.
	AC estimate returns the estimate of the input signal AC level in volts rms when the input Signal is in volts.
	DC estimate returns the estimate of the input signal DC level in volts if the input Signal is in volts.

AC & DC Estimator Details

You often need to measure the AC and DC content of signals you digitize. This VI applies the Hanning window, which is sufficient for separating most of the AC energy from the DC bin. If you have a periodic signal and you do not have an integral number of periods in the acquisition, spectral spreading occurs regardless of whether you perform an FFT later. The coherent gain and equivalent noise bandwidth constants for the Hanning window that this VI uses compensate for windowing effects on the gain and bandwidth.

LabVIEW uses the efficient mean and variance computations instead of Fourier analysis to determine the total AC energy and the true DC level.