The invention concerns a method for detecting misbehaviour of a mechanically based flow meter. The method comprises the steps of reading a primary flow signal of the flow meter several times per mechanical cycle; analysing the readings to find periodical, time-dependent variations; producing a current representation of the variations; and comparing the current representation with a corresponding normal representation which represents correctly operating meters of the same type, and detecting significant differences, if any.
Godkänd; 1999; 20060926 (ysko)