Instrument Mesurement Knowledge

Causes and Solutions of Abnormal Zero Point of Electromagnetic Flow Meter

Views: 5     Author: Site Editor     Publish Time: 2021-08-26      Origin: Site

1. The pipeline is not filled with liquid, or the liquid contains bubbles


A. If the liquid in the pipeline is not full, the electromagnetic flow sensor should be moved to a full position when it is installed horizontally; When the electromagnetic flow sensor is installed vertically, the liquid flow should be from bottom to top.

B. If there are bubbles in the pipeline, install getter or automatic exhaust valve upstream of the sensor.

2. Zero instability of electromagnetic flowmeter is caused by tiny flow in pipeline

The pipeline shut-off valve has poor air tightness, which misunderstands the tiny leakage measured by electromagnetic flowmeter as the unstable zero point of flowmeter 

a. The valve has poor air tightness due to long service time or dirty liquid

b. Besides the main pipeline, there are several branch pipes, forgetting to close the valves of the branch pipes

3. External interference such as stray current will lead to zero instability

a. Eliminating external interference such as stray current in pipeline mainly depends on good grounding of electromagnetic flowmeter. Generally, the grounding resistance is less than 10ω. What's important is that it can't be grounded with other electrical appliances.

b. When the flow sensor is installed on the plastic pipe, the pipe with insulating coThe sensor should be far away from the motor, engine and other devices that may cause interference.ating and paint. It is necessary to install grounding rings at both ends of the sensor to ensure sufficient contact between the measured medium and the sensor housing. Ensure the normal operation of electromagnetic flowmeter.

c. Magnetic flow sensors should be kept away from motors, engines and other equipment that may cause interference.

4. The conductivity of the measured medium is uneven

Install the flow sensor in a place with constant or uniform conductivity, avoid being close to the dosing point, and avoid installing the flowmeter downstream of the pipeline with insufficient chemical reaction.

5. Low conductivity will cause zero drift

6. The insulation of the instrument signal line is reduced

Insulation of signal lines and their terminals is reduced due to moisture, water, acid mist, etc.