Why does the electromagnetic flowmeter cause errors?

So what are the causes of electromagnetic flowmeter errors?

(1) The tube is not full of liquid. When there is a small amount of gas in the tube, the measurement result will deviate from the actual value, causing a small error; when there is a lot of gas, the measurement value will be unstable and the output will shake. At this time, the measurement value cannot be used as the correct result.

(2) The measured liquid contains solid components. It will cause the electrode surface to be contaminated, cover the electrode or lining, resulting in a decrease in the flow area and a gradual decrease in the flow value. If there is conductive material in the sediment layer, the flow signal is likely to be short-circuited, causing the instrument to malfunction.

(3) Improper selection of electrodes or grounding rings. When the electrode contacts the measured fluid medium, the electrochemical reaction of the measured medium will generate polarization voltage. Whether the electrode can reliably detect the flow signal is crucial to the performance of the flow meter. The grounding ring forms an electrical connection with the medium and is connected to the zero potential through the grounding wire. When the process pipeline connected to the sensor is plastic or has an insulating coating, a grounding ring must be installed, otherwise the instrument will not work properly. There are many kinds of materials for electrodes and grounding rings, so be careful when choosing.

Electromagnetic flowmeter is a widely used flow measurement instrument, which is often used for sewage and wastewater measurement and has high cost performance. However, improper selection, installation or use may also cause errors in the measurement results and even damage the instrument.