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Description of common faults and troubleshooting methods of electromagnetic flowmeter

There are two kinds of common faults in the operation of electromagnetic flowmeters: one is the failure of the instrument itself, that is, the fault caused by the damage of the instrument structural components or components; the other is the fault caused by external causes, such as improper installation of flow distortion, deposition and junction. Scale and so on. We discuss these two types of faults.
First, the meter has no flow signal output
1. Cause analysis
Such faults are more common during use. The reasons are generally: (1) the meter is not properly powered; (2) the cable connection is not normal; (3) the liquid flow condition does not meet the installation requirements; (4) the sensor component is damaged or measured. The inner wall has an adhesive layer; (5) the converter components are damaged.
2. Solution
(1) Confirm that the power supply has been connected, check whether the voltage of each output of the power circuit board is normal, or try to replace the entire power circuit board to judge whether it is good or bad.
(2) Check if the cable is intact and the connection is correct.
(3) Check the direction of liquid flow and whether the liquid in the tube is full. For electromagnetic flowmeters that can measure forward and reverse, if the direction is inconsistent, it can be measured, but the set display flow rate does not match the positive and negative directions and must be corrected. If the sensor is too large, you can change the direction of the arrow on the sensor and reset the display meter symbol. If the pipeline is not filled with liquid, it is mainly caused by improper installation of the sensor. Measures should be taken during installation to avoid causing the liquid in the pipeline to be unsatisfactory.
(4) Check whether the electrode on the inner wall of the transmitter is covered with a liquid crust layer. For the measurement liquid that is easy to scab, it should be cleaned regularly.
(5) If it is determined that the converter component is damaged due to damage, replace the damaged component.
Second, the output value fluctuations
1. Cause analysis
Most of these failures are caused by the measurement medium or the external environment. After the external interference is removed, the fault can be eliminated by itself. In order to ensure the accuracy of the measurement, such failures can not be ignored. In some production environments, the vibration of the measuring pipe or liquid is large, which may cause the circuit board's circuit board to loosen, which may also cause fluctuations in the output value.
2. Solution
(1) Confirm whether the flow is actually caused by the process operation. At this time, the flowmeter only reflects the flow condition as it is, and the fault can be eliminated by itself after the pulsation is over.
(2) Electromagnetic interference generated by external stray currents. Check whether the instrument is in a working environment with large electrical appliances or welding machines. Make sure that the instrument is grounded and the operating environment is good.
(3) When the pipe is not filled with liquid or the bubble contains bubbles, both are caused by process reasons. At this point, the process technician can be requested to confirm that the output value can be restored after the liquid is full or the bubble is recovered.
(4) The transmitter circuit board is a plug-in structure. Due to the large vibration of the pipeline or liquid in the field, the power supply board of the flowmeter is often loosened. If loose, remove the flowmeter and re-fix the board.
Third, the flow measurement value does not match the actual value
1. Cause analysis
Such faults are generally caused by: (1) whether the transmitter circuit board is intact;
(2) When the liquid flow rate is too low, the measured liquid contains tiny bubbles, and the bubble rises gradually gathers above the pipe, and the liquid flow area changes. When the gas is too much, an interference signal is generated, which affects the measurement accuracy;
(3) The signal cable is not well connected or the insulation performance of the cable is reduced during use, resulting in inaccurate measurement;
(4) The parameter setting value of the converter is not accurate.
2. Solution?
(1) Check if the transmitter circuit board is intact. If the junction box is ingress or corroded by corrosive liquids, electrical performance may be degraded or damaged. The board should be replaced at this time.
(2) Ensure that the flow rate of the liquid to be measured in the pipeline is above the minimum flow limit to enable the transmitter to work properly.
(3) Check the signal cable connection and the insulation performance of the cable. If the signal cable is loose, reconnect it. If it is checked that the insulation of the cable does not meet the insulation requirements, you need to replace the cable.
(4) Re-set the converter set value and check the zero and full scale values of the converter.
Fourth, the output signal super full measurement range?
1. Reason analysis?
(1) There is an error in the signal cable wiring or the cable connection is broken;
(2) The parameter setting of the converter is incorrect;
(3) The converter does not match the sensor model.
2. Solution?
(1) Check if the signal loop connection is normal or not. If the signal loop is disconnected, the output signal will be overfull. In this case, the signal cable should be reconnected correctly. At the same time, it is necessary to check whether the insulation performance of the cable is intact. If it does not meet the requirements, a new cable needs to be replaced.
(2) Check in detail the parameters of the converter and whether the zero point and full scale meet the requirements.
(3) If it is checked that the model of the converter and the sensor are not matched, you need to contact the factory for exchange. ?
Five, zero instability?
1. Cause analysis
(1) The pipe is not filled with liquid or contains bubbles in the liquid.
(2) Subjectively, there is no flow in the tube pump liquid and there is actually a slight flow.
(3) Reasons for liquids (such as poor conductivity of liquid conductivity, electrode contamination, etc.).
(4) The signal loop insulation drops.
2. Solution?
(1) The pipe is not filled with liquid or the bubble in the liquid is the process reason. At this time, the process personnel should be requested to confirm that the output value can be restored after the process is normal.
(2) There is a slight flow in the pipe, which is not a malfunction of the electromagnetic flowmeter.
(3) If the impurity deposits on the inner wall of the measuring tube or on the inner wall of the measuring tube, or the electrode is contaminated, there may be a zero point change. At this time, it must be cleaned; if the zero point does not change much, try to re-zero.
(4) Due to environmental conditions, dust, oil, etc. may enter the watch case. Therefore, it is necessary to check whether the insulation of the electrode part is lowered or destroyed. If it does not meet the insulation requirements, it must be cleaned.

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