What is the quadrature interference of electromagnetic flowmeter

The two electrodes of the electromagnetic flowmeter sensor, the measured liquid, and the internal resistance of the amplifier form a closed loop, which is equivalent to a one-turn transformer secondary winding, the excitation coil is equivalent to the primary coil, and the closed loop is equivalent to the secondary coil. Since the closed loop cannot be completely parallel to the magnetic field, there are always some magnetic lines of force passing through, so even if the flow velocity is zero, an induced voltage will be generated, which is the "transformer effect".

The interference electromotive force is obtained according to Lenz's law:

It can be seen that ew is related to the excitation frequency and has nothing to do with the measured liquid flow. The interference signal is 90° behind the flow signal of the electromagnetic flowmeter, so the interference electromotive force is called the quadrature interference. Since the quadrature interference is the differential of the magnetic induction intensity B to the time t, it is also called the differential interference.