Method and circuit arrangement for measuring fluid flow velocity by measuring acoustic transit time differences

摘要

The method determines the start time of a packet of high frequency oscillations triggered on the basis of an external excitation. The times relative to a predetermined zero point at at least two points on the envelope of the oscillation packet are determined, in a controller-analyser (30). One of these is a characteristic envelope curve point. The other is an amplitude equal to a predetermined break point of the amplitude of the characteristic curve point. The digitised sample values of a transducer current which flows with a particular excitation are compared with digitised sample values of the excitation current of a transducer in a contrasting state, which are stored in a memory of the analyser (30). The resulting difference values are analysed for error detection.