| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an electromagnetic flow meter performing two-frequency excitation capable of effectively removing an influence of differential noise and highly precisely extracting an attachment signal. <P>SOLUTION: An electromagnetic flow meter gives a magnetic field by a synchronized high-frequency excitation signal and a low-frequency excitation signal to a fluid flowing inside a measuring tube, and measures a flow rate of the fluid based on a detection signal generated in a pair of detection electrodes provided in the measuring tube. The electromagnetic flow meter includes: an earth electrode provided inside the measuring tube and defined as a reference potential when measuring the flow rate; attachment signal imparting means connected to the detection electrodes and generating an AC signal for diagnosing an attachment synchronized with the high-frequency excitation signal and having an integer multiple frequency; and a diagnosis attachment diagnosing section computing the amount of the attachment based on a sample voltage signal between the detection electrodes sampled at a plurality of continuous half cycles and synchronised with the AC signal before a polarity reversal timing of the low-frequency excitation signal. <P>COPYRIGHT: (C)2012,JPO&INPIT |
