Five-step method to solve the instability of zero point of intelligent electromagnetic flowmeter

Update:11 Jun 2021
Summary:

Industrial production often encounters the unstable sta […]

Industrial production often encounters the unstable state of resetting of intelligent electromagnetic flowmeters. There are many reasons for this problem. According to the experience of the technicians of Zhongyi Meter for many years, there are mainly the following factors:
1. The pipeline is not filled with liquid or the liquid contains bubbles. Objectively speaking, there is no activity in the flow sensor, but there is a trace activity in practice.
2. The long-term use of the valve or the incomplete sealing of the valve due to liquid contamination can also lead to the appearance of zero point instability.
3. The change or unevenness of the conductivity of the liquid will cause the zero point to change when it is still, and the output will sway when it is active.
4. Because the scale of the inner wall surface and the electrode contamination level cannot be completely the same and symmetrical, the balance of the initial zero adjustment setting is destroyed.
5. The change in the state of the power equipment near the flow sensor (such as an increase in leakage current) constitutes a change in the ground potential, which will also cause a change in the zero point of the intelligent electromagnetic flowmeter.
Through the analysis of the problem, we can find out the corresponding solution according to the corresponding phenomenon.
One first exclude inspection: inspection procedures
Check the unstable process of the zero-point intelligent electromagnetic flowmeter. First, make a preliminary investigation and judgment according to the process, and then carefully check and try to eliminate the fault. The order of the inspection items listed in the process is:
(1) Observation or inquiries can be made to understand that there is no need for major operations first, that is, easy first and difficult later;
(2) According to the past on-site maintenance experience, the frequency of occurrence is higher, and the probability of occurrence in the future is higher;
(3) The order and requirements of the inspection itself. If the cause of the failure is confirmed after preliminary investigation, it can also be carefully inspected in advance.
Second, the intelligent electromagnetic flowmeter sensor is not perfect according to the ground and is subject to external interference such as stray current:
Pipeline stray current and other external interference affect the main intelligent electromagnetic flowmeter to have good grounding protection. It is usually required that the grounding resistance is less than 1000, and do not share the grounding with other motors. Sometimes the environmental conditions are good, and the intelligent electromagnetic flowmeter can be normal without grounding Work, but once a good environment does not exist, the instrument will malfunction, and then the inspection will cause more trouble.
Changes in the state of the power equipment near the flow sensor (such as increased leakage current) form a ground potential change, and electricity will cause the zero point of the intelligent electromagnetic flowmeter to change.
3. Reasons for the liquid of the intelligent electromagnetic flowmeter (such as the uniformity of liquid conductivity, electrode contamination, etc.);
The change or unevenness of the conductivity of the liquid will cause the zero point to change when it is stationary, and the output will slosh when it flows. Therefore, the position of the flowmeter should be far away from the injection point or the downstream of the chemical reaction section of the pipeline. The flow sensor is best installed upstream of these places.
If the liquid contains a solid phase, or impurities deposit on the inner wall of the measuring tube, or scale on the inner wall of the measuring tube, or the electrode is contaminated by grease, etc., there may be zero point changes. Because the scale of the inner wall surface and the degree of contamination of the electrode cannot be completely The same and symmetrical, destroy the balance of the factory's initial decay setting. Active measures are sufficient to remove the dirt and deposits; if the retailer Dial thermometer housings Manufacturerschanges little, you can also try to reset the zero.
Four, intelligent electromagnetic flowmeter
The insulation of the signal circuit has dropped.
If the liquid contains a solid phase, or impurities deposit on the inner wall of the measuring tube, or scale on the inner wall of the measuring tube, or the electrode is contaminated by grease, etc., there may be zero point changes. Because the scale of the inner wall surface and the degree of contamination of the electrode cannot be completely The same and symmetrical, destroy the balance of the factory's initial decay setting. Active measures are sufficient to remove the dirt and deposits; if the retailer changes little, you can also try to reset the zero.
The signal circuit insulation decline will cause zero point instability. The reason for the signal circuit insulation decline is sufficient, and it is caused by the insulation decline of the package pole, but it cannot be ruled out that the signal cable and its wiring terminal insulation decline or damage. Because sometimes
The on-site environment is very harsh. A slight negligence of the instrument cover/wire connection is inadvertently sealed, and moisture, acid mist or dust particles invade the instrument junction box or cable protection layer, which will reduce the insulation. Check the insulation resistance of the signal circuit respectively.
The cable side and the flow sensor side are divided into two parts, using a megohmmeter to test. Because the signal cable is easy to do first. The flow sensor is divided into two parts: the liquid is filled to measure the electrode surface contact resistance and the tube, and the U pole is insulated resistance.

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