| 摘要 |
<p>An electromagnetic flowmeter for water conveyance in a semifull state, whose measurement error caused by the change of the conductivity of a fluid can be reduced. A main body section (24) of the flowmeter has two excitation coils (Cu, Cl) capable of being excited independently and a pair of electrodes (22) facing to each other. A transducer section (32) comprises a preamplifier (27), two amplifying circuits AMPu, AMPl, each of which includes an offset compensation circuit (O. C.), an integration circuit (I.), and a sample-and-hold circuit (S/H), a switch (S1), and A/D converting circuit (30), a processing circuit (31), a short- circuit resistor (Rs), a short-circuit switch (S2), an excitation circuit (25), an excitation timing circuit (26) for exciting, and a timing circuit (28) for measuring a conductivity. The error of measuring a flow rate, which is caused by the change of the conductivity, is corrected by operating the short-circuit switch (S2) through the timing circuit (28) for measuring the conductivity. <IMAGE></p> |
