Signal amplifier circuit of electromagnetic flowmeter

Abstract

The present invention provides a signal amplifying circuit of an electromagnetic flowmeter, which can avoid deterioration of CMRR in a differential amplifying circuit caused by a coupling capacitor and delay in recovering from an abnormal input. The flow signal input between the flow signal input terminals (T1, T2) of the connector (CN1) is input to one and the other of the input terminals of the instrument amplifier U3 through the resistance element (R1, R2) and differentially amplified, The amplified output signal (V3) is output to the sample and hold circuit (13) through the coupling capacitor (C1). In addition, the flow signal input to the flow signal input terminal (T1, T2) of the connector (CN1) is buffered by the buffer amplifier (U1, U2), and the output signal (V1, V2) is output to the abnormality detection circuit (14 ). At this time, guard the wiring patterns (L1, L2) connecting the flow signal input terminals (T1, T2) and the non-inverting input terminals of the buffer amplifiers (U1, U2) with guard ring patterns (GR1, GR2).

Description

technical field [0001] The invention relates to an electromagnetic flowmeter, in particular to a signal amplifying circuit technology for amplifying electromotive force obtained from a detector. Background technique [0002] In general, in an electromagnetic flowmeter that measures the flow rate of a conductive fluid, an excitation current that alternates in polarity is supplied to the excitation coil to detect the electromotive force generated between a pair of detection electrodes, and a signal amplification circuit is used to detect the electromotive force generated between a pair of detection electrodes. Differential amplification, sampling the obtained flow signal and performing signal processing, thereby measuring the flow rate of the fluid flowing in the pipe, wherein the excitation coil is arranged so that the magnetic field generation direction and the flow direction of the fluid flowing in the pipe Perpendicularly, the pair of detection electrodes are arranged in t...

AI Technical Summary

Problems solved by technology

[0006] In addition, the input impedance of the FET-input operational amplifier is very high, and the input bias current is also very small, but it is easily affected by noise, etc. generated by peripheral circuits.

In addition, if the insulation properties of the substrate deteriorate due to the influence of surrounding humidity or the adhesion of foreign matter, the input impedance will decrease.

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