Why does the electromagnetic flowmeter display a negative value?

Famimet Electromagnetic Flowmeter

The reason why the electromagnetic flowmeter displays a negative value after being connected may involve many aspects, mainly including the following aspects:

Installation direction is wrong:

If If the sensor of the electromagnetic flowmeter is not installed correctly according to the flow direction mark, and the fluid flow direction is opposite to the direction set by the flowmeter, the measurement direction will be opposite and a negative value will be displayed. At this time, it is necessary to reinstall the flow meter and ensure that the sensor is installed according to the flow direction mark.

The signal wire is connected reversely:

Since the electromagnetic flowmeter has forward and reverse flow measurement functions, if the signal wire is connected reversely, the flowmeter may display reverse flow. The solution to this problem is to swap the sensor signal wires and connect them correctly.

The pipe is not filled with medium:

If the measuring pipe is empty or is not completely filled with medium, and there are gas or bubbles, the flow meter may display a negative number or the flow value may fluctuate. At this time, methods such as warp reduction or tilted installation can be adopted to ensure that the pipe is filled with the measured medium and that the flowmeter is ready for measurement. In addition, when the valve is opened, the instantaneous flow rate may also cause the pipeline liquid to flow back, resulting in a negative value.

Leaking or damaged electrodes:

Leaking or damaged electrodes may cause unstable measurement signals, resulting in erroneous flow displays, including negative values. At this time, the status of the electrode needs to be checked. If there is leakage or damage, the electrode should be replaced in time.

Inner wall adhesion layer:

If an adhesion layer accumulates on the inner wall of the electromagnetic flowmeter, especially the insulation layer, it may cause an open circuit in the electrode circuit, making the flowmeter unable to work normally, or even displaying negative value. Therefore, the adhesion layer on the inner wall of the flow meter needs to be cleaned regularly to ensure that the electrode circuit is smooth.

Lightning or electromagnetic interference:

Lightning or strong electromagnetic field interference may introduce high voltage and surge current through the power line or signal line, causing the flow meter to display abnormally, including negative values. At this time, it is necessary to strengthen lightning protection and electromagnetic interference measures, such as installing lightning arresters, and taking shielding and grounding measures to reduce electromagnetic interference.

Changes in environmental conditions:

Changes in environmental conditions such as strong magnetic fields and stray currents may also affect the normal operation of the flow meter, causing a negative value to be displayed. For environments with strong magnetic fields and stray currents, appropriate isolation and protection measures should be taken.

Converter failure:

A converter that fails may process the flow signal incorrectly, causing a negative number to be displayed. If you suspect that the converter is faulty, you should contact after-sales service for inspection and repair.

Changes in fluid characteristics:

Bubbles or solid particles contained in the liquid to be measured, especially when the bubbles are large enough to cover the entire electrode surface, may cause output signal fluctuations or even Display negative numbers. For fluids containing bubbles or solid particles, an appropriate flow meter type should be selected or pretreatment measures should be taken.