Electromagnetic flowmeter measurement accuracy inaccurate factors

Electromagnetic flowmeter is an instrument produced based on the principle of electromagnetic induction to measure the volume flow of conductive media in pipelines. This article discusses the situation where the electromagnetic flowmeter affects the accuracy during the measurement of medium flow.

1. If the measured medium contains metal, the electrodes of the electromagnetic flowmeter are prone to short circuit. At this time, the value measured by the electromagnetic flowmeter is obviously too small or zero. This situation does not often happen during normal production. When measuring high-viscosity media, because it easily adheres to and precipitates on the pipe wall, the fluid wraps around the electrode, reducing the conductivity of the medium. The electrode signal does not work properly, and an electrode short circuit occurs. If the precipitate is a non-conductive layer, it will cause the electrode to open circuit and the electromagnetic flowmeter will not work properly. If it is a metal precipitate, its conductivity is greater than the liquid conductivity, and the actual flow value will be higher than the measured flow value. If the sediment is a scale layer, the conductivity of the measured medium is higher than the sediment, and the measured value will be smaller than the actual flow value.

2. The electromagnetic flowmeter has more opportunities to measure slurry or dirt than other flow meters, and the probability of an adhesion layer on the inner wall affecting the accuracy is relatively high. If the conductivity of the adhesion layer is similar to the conductivity of the medium being measured, the flow meter can output signals normally, but the flow area is changed, which is a hidden fault that affects the measurement accuracy error; if the adhesion layer has a high conductivity, the electromotive force between the electrodes will be short-circuited; if it is insulated There is a permanent adhesion layer, and the electrode surface is insulated and the measurement circuit is disconnected. In the latter two cases, the electromagnetic flowmeter cannot work properly.

3. The impact of environmental changes on the electromagnetic flowmeter. During the debugging period, the environmental conditions are still good and the electromagnetic flowmeter works normally. At this time, it is often easy to ignore the installation conditions. In this case, the environmental conditions change. , a new interference source appears during operation, which interferes with the normal operation of the electromagnetic flowmeter, and the output signal of the electromagnetic flow rate will fluctuate.

4. The impact of lightning strikes on electromagnetic flowmeters. Lightning strikes the circuit and induces high voltage and transient surge current, which will cause damage to the flowmeter instrument. Therefore, it is very important to provide lightning protection facilities in the power line control room to prevent lightning strikes on the electromagnetic flowmeter.

The electromagnetic flowmeter has no rotating parts and no parts that prevent the flow of fluid, so there is no pressure loss. The electromagnetic flowmeter is also very convenient to install. It can be installed horizontally, vertically or tilted. It has high measurement accuracy and a large range. The measured medium only contacts the pipe lining and electrode of the electromagnetic flowmeter. The material is corrosion-resistant and wear-resistant. Just make a reasonable choice.

As the use time increases, the accuracy of the electromagnetic flowmeter will decrease. In order to extend the service life and ensure the best measurement accuracy, the following points should be done:

1. Strengthen the electromagnetic flowmeter. The operation and management of the flowmeter must promptly discharge the residue of the sensor. The electromagnetic flowmeter sensor does not have a sewage pipe and must be separated and eliminated manually.

2. Electromagnetic flowmeters are greatly affected by the environment. After the electromagnetic flowmeter is installed and debugged on site, try to eliminate or avoid new interference factors on measurement accuracy caused by environmental changes.