NONCONTACT MEASURING DEVICE FOR VOLUME OR MASS OF FLOW OF MOVING MEDIUM

The arrangement for contactless measurement of the volume flow or mass flow of a moving medium comprises two transducers which furnish electrical signals into which inhomogeneities of the moving medium enter depending on their spatial position in accordance with different spatial weighting functions. The detecting regions of the two transducers are offset with respect to each other in the direction of movement of the medium but partially overlap in such a manner that the gradient of the spatial cross correlation function for the spatial displacement zero is different from the zero vector. A correlator forms the time cross correlation function of the two signals and an evaluation circuit derives the measured value for the volume flow or mass flow of the moving medium from the gradient of the time cross correlation function for the time displacement zero. Alternatively, the measured value may also be derived from the first moment of the cross power density spectrum of the two signals because said moment is mathematically equivalent to the gradient of the time cross correlation function of the two signals for the time displacement zero.