Electromagnetic flowmeter measurement method

Case introduction

The fluids in pipelines often have completely different properties.

Let us analyze how this measurement method works:

The inner wall of the electromagnetic flowmeter measuring pipe is lined to prevent the conductive liquid from short-circuiting the metal pipe. When the liquid is not flowing, any induced voltage is not measured between the two electrodes. Charged particles in a conductive liquid are evenly distributed. As soon as the liquid starts flowing in the measuring tube, the magnetic field exerts a force on the charged particles, and the positive and negative charged particles in the liquid separate and concentrate on both sides of the tube wall.

At this time, the two electrodes will detect the voltage waveform and measure it. The voltage is proportional to the flow rate of the fluid in the pipe, and the actual volumetric flow rate can be calculated. The greater the flow rate, the greater the separation of charged particles. Therefore, the greater the voltage measured between the electrodes. In practice, the electrodes measure the interference voltage and simultaneously measure the true voltage.

And the interference voltage must be separated from the real signal. Using DC pulses to form a magnetic field is a successful method to separate theinterference voltage. In this way, the polarity of the magnetic field is alternately exchanged, and the voltage obtained by measuring the motor will continue to change the magnetism. This eliminates all constant interference voltages. Examples include electrochemical effects in liquids or electromagnetic effects from external magnetic fields. In this way, the size of this interference voltage will not have no impact on the detection signal. The advantage is that the measurement is stable and the system zero point is stable.