Measurement uncertainty estimation of a virtual instrument

The law of uncertainty propagation is applied to a PC-based virtual instrument. According to the "guide to the expression of uncertainty in measurement", the measuring model and the various sources of uncertainty have been taken into account. The expressions of the combined output uncertainty in various basic digital signal processing blocks, are obtained starting from each input sample absolute accuracy, without taking into account the parameters which regard the overall behavior of an acquisition board, such as the effective number of bits. In order to verify this procedure, the results obtained by means of the theoretical analysis, are compared with the ones obtained from numerical simulation. Then the results of experimental tests are presented to validate the proposed method. In particular, a virtual instrument, with a complex measurement chain for flicker evaluation, has been considered. The results are in a good agreement with the theoretical and numerical ones.