Abstract: The electromagnetic flowmeter has a wide range of applications, measuring range and other characteristics, and the maintenance rate is also low in the later stage. These advantages must be established in the previous correct selection and installation, if not strictly in accordance with the operating instructions. Installation, in the later use process, there will also be a certain failure rate.

1. Error caused by fluid distribution in the pipeline

1. Under normal conditions, the fluid distribution in the pipeline is axially symmetric and uniformly distributed in the magnetic field. The magnitude of the electromotive force generated by the electromagnetic flowmeter electrode is independent of the fluid flow velocity and proportional to the average flow velocity of the fluid. .

2. In the case of non-axisymmetric distribution, the geometrical position of each fluid particle of the fluid is different with respect to the electrode. Similarly, the electromotive force produced by the counter electrode is also different. When the electrode is closer to the electrode, the velocity The electromotive force generated by the large mass point is also large, causing an error.

3. In order to avoid the error caused by the non-axisymmetric distribution of the fluid in the pipeline, the distance between the upstream and downstream straight pipes of the electromagnetic flowmeter should be kept as much as possible during installation to reduce the error.

2 , the error caused by fluid conductivity

The electromagnetic conductivity of the electromagnetic flowmeter has certain requirements, which must be 5 μs/cm . When the conductivity of the fluid decreases during operation, the electrode output impedance of the electromagnetic flowmeter is increased, and the input impedance of the converter is increased. The resulting load effect produces an error.

3 , the electrode caused by the attachment of the error

This kind of error usually does not occur in the initial installation. When measuring the fluid with sediment, and the electromagnetic flowmeter is used for a period of time, the probability of occurrence is large. When the surface of the electrode is attached, it often causes The zero point of the electromagnetic flowmeter flutters, so for measuring such fluids, the attachments on the electrode surface of the electromagnetic flowmeter should be cleaned regularly to avoid the occurrence of errors;

4 , the error caused by the length of the cable

1. The error caused by the cable line generally appears on the split type electromagnetic flowmeter. In the signal transmission of the electromagnetic flowmeter, the shorter the cable line, the smaller the signal loss will be. The split type electromagnetic flowmeter is standard at the factory. a 10 meter cable;

2. When the user's 10 meter cable is not enough, then it is necessary to consider the problem of lengthening the cable. Due to the loss of the signal, the maximum length of the cable must be considered.

3. Therefore, when selecting the line, the ordinary cable is selected differently. Because the double-core two-layer shielded cable is selected, the maximum length between the converter and the sensor of the electromagnetic flowmeter can be effectively extended;

Summary: For the cable length problem of the split electromagnetic flowmeter, usually the 10 meter cable we have is enough for the user. For the problem of lengthening the cable, many users will ignore this small detail, so usually in the case of errors Can not find the reason, in the details of the electromagnetic flowmeter installation should pay attention to

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