ELECTROMAGNETIC FLOW METER

摘要

A first A/D conversion unit (26) converts an analog flow signal (i.e., a flow signal component and noise component) supplied from an AC amplifier circuit (22) to a digital signal. Given, for example, one period of an excitation frequency fex as a prescribed interval, the values of the digital signal from the first A/D conversion unit (26) are sampled for the prescribed interval at a sampling time, which is generated at the prescribed period, and accumulates such, together with the sample timings, as sample data in the sample data group storage unit (28D). After the accumulation is complete, the sample data and the normal data corresponding to the same sampling time are read out from the sample data group storage unit (28D) and a normal data group storage unit (28C), respectively, and the average value of the absolute values of the differences between the sample data and the normal data is calculated as a noise factor NF (i.e., a noise evaluation value). If the noise factor NF exceeds a diagnostic threshold value SPNF, then it is determined that foreign matter is adhered to electrodes.