Magnetic flowmeter with pulsating field - has increased scan frequency and voltage controlled resistor suppressing unwanted oscillations

摘要

A magnetic flowmeter with a pulsating magnetic field has a field coil arrangement producing a magnetic field in the measurement tube carrying the fluid. It achieves accurate measurements whilst enabling a higher scanning frequency to be used. A voltage controlled resistor (3) and a capacitor (2) connected in series form a circuit connected in parallel with the field coil (2). The voltage controlled resistor presents a high impedance path for applied voltages below a threshold level and a low impedance for higher voltages. The transition voltage is greater than the voltage amplitude of the damped oscillation of the oscillator formed by the field coil and capacitor. Unwanted oscillations are thus suppressed whilst the scanning frequency can be raised.