Electromagnetic flowmeter is widely used in wastewater treatment, water drainage and supply, agricultural irrigation system, etc. Here are the frequently asked questions about electromagnetic flow meter's operation and installations.
Q1: The electromagnetic flowmeter display screen is black when it is powered on.
(1) Check the power supply. The power supply of flow meter can be 220V AC, 24V DC, or 12V DC; check whether the power supplied to the instrument is consistent with the required voltage.
(2) Check the wiring. 220V (AC) and 24V/12V (DC) connection terminals are all reserved on the terminal board at the rear of the instrument. Check whether the power wiring is correct. Please pay special attention and do not misconnect to the wiring terminal of 220V AC and that of 24V DC. If there is no problem with the wiring, it is also necessary to check whether the wiring is reliable to prevent virtual connection.
(3) Check the screen connection. Need to re-plug the cable. This situation occasionally occurs in installation environments with frequent vibrations. The current screen is connected to the signal board through the connection line, and in rare cases, the connection of the connection line is poor and needs to be rechecked.
Q2: The flowmeter is powered on, and there is a flow display when there is no water.
(1) When the meter is powered on, a small flow will appear, and the duration is about 15S ~ 30S. The flow value will fluctuate non-stop and may be positive or negative. This situation is normal and belongs to the self-test behavior when the flowmeter is turned on.
(2) When the pipe is empty, the flowmeter value keeps jumping. This situation is generally caused by the unreasonable setting of the empty pipe alarm threshold or the prohibition of the empty pipe alarm. It is necessary to reset the empty pipe alarm threshold according to the actual situation on site or turn on the empty pipe alarm function.
(3) The pipe is full, but the data of the flow meter jump consistently. If the jitter data is very small, you can solve the problem by cutting out small signals. If it is large, there is a problem with the customer's field-wiring generally, and it is necessary to re-check the wiring method of the signal line and the excitation line.
Q3: The value collected by the 4-20mA current signal does not match the value displayed on the flowmeter.
(1) The flow range marked on the electromagnetic flowmeter is the full-scale range that meets the measurement accuracy, so the 4mA current corresponds to 0 cubic m³ / h, and 20mA corresponds to full-scale flow.
(2) Once customers adjust the full scale of the instrument, then the PLC or the acquisition end also needs to modify the full-scale corresponding to 20mA.
(3) Check which current output mode is set in the instrument, the electromagnetic flowmeter can output both 0 ~ 10mA current and 4 ~ 20mA current.
Q4: After flow through the meter, the deviation between the displayed flow and the estimated flow value on site is large.
(1) Check the installation, the meter should meet the installation conditions of 5 times diameter in front and 3 times diameter behind.
(2) Check the instrument parameters to see if the tube diameter and sensor coefficient have been reset.
(3) Check whether the pipeline is full.
Q5: After flow through the meter, the field data jumps violently.
(1) Check whether the installation condition is 5 times diameter in front and 3 times diameter behind.
(2) Check whether there is a large amount of air in the pipeline.
(3) Check whether there is severe vibration in the pipe.
We mention the 5D in front and 3D behind.
Q 6: What should I pay attention to when installing the electromagnetic flowmeter?
(1) Choose the right installation position.
In order to ensure the normal operation of the flow meter and reduce the measurement error, the water pipe flow meter should meet certain straight pipe requirements in front and behind. According to the test standard requirements of JJG1033-2007 "Verification Regulations for Tap Water Flow Meter", usually the front straight pipe section should reach 10D(diameter) and the rear straight pipe section should be 5D(diameter); according to practical experience, in most applications, the front straight pipe section of the flowmeter should be at least 5D(diameter), The rear straight pipe section should be at least 3D(diameter).
Since the drinking water flowmeter measures a weak electric potential, it is necessary to eliminate all external interferences for accurate measurement. Therefore, good grounding is necessary to ensure the stable operation of the flowmeter. Generally, the grounding is achieved through the grounding ring or the reference electrode in the sensor and the grounding connection in the piping system.
(2)Pay attention to the installation condition.
When installing the electromagnetic flowmeter, try to avoid valves and tees.
Here is a picture showing the wrong installation of the electromagnetic flowmeter below.
The electromagnetic flowmeter is installed at the rear end of the gate valve. When the water flows through the gate valve, bubbles and vortices will form, causing the flowmeter data to jump violently and the measured value is not accurate.
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