PURPOSE: To provide a low frequency exciting system magnetic flow meter which is excellent in stability and response of a zero point, by a method wherein an exciting current periodically fed to an exciting coil is turned ON and OFF not less than 2 times, a voltage induced between electrodes is sampled when the exciting current is brought to a positive or a negative stationary value and zero, and an offset voltage in an induced voltage and an eddy current noise are removed by means of its signal.
CONSTITUTION: A switch 12 is controlled by a drive pulse P1, and a current flowing through an exciting coil 21 is switched through the working of a switch 13 to a forward direction when the P1 is brought to ON, and to a reverse direction when the P1 is brought to OFF. The switch 13 is controlled by a drive pulse P2. An inducing voltage ea, corresponding to an exciting current IW, is generated between electrodes 23a and 23b. In addition to a signal component proportioning a flow rate F of fluid flowing through a pipe 22, a noise component produced as a result of switching of the exciting current, and an offset voltage Vno are overlapped with the induced voltage ea. A computation is substantially conducted by a signal processing circuit 3, and only signal components Vs1WVs4 proportional to a flow rate of fluid can be obtained.
GOTOU SHIGERU
IKEMI MOTOYOSHI
| JPS5375966A | 1978-07-05 |