What are the reasons for the inaccurate measurement of an electromagnetic flowmeter?

The core reasons for inaccurate measurement of electromagnetic flowmeters fall into four categories: medium state, instrument installation, equipment wear, and parameter settings. Details are as follows:

1. Medium state does not meet measurement requirements

• The pipeline is not fully filled with medium or there are air bubbles, resulting in insufficient magnetic field cutting and disordered signals.
• The medium’s conductivity is lower than the instrument’s threshold (usually <5μS/cm), making it impossible to form an effective induced current.
• The medium contains a large amount of impurities and sediments, which adhere to the electrode surface or interfere with the flow field.

2. Improper installation position/method

• Insufficient straight pipe sections before and after (failing to meet the requirement of 10D before and 5D after, where D is the pipe diameter), or being close to pumps, valves, or elbows, causing flow field distortion.
• Unreasonable electrode installation position, such as at the top (air accumulation) or bottom (slag accumulation) of the pipeline, failing to fully contact the medium.
• The medium flow rate is outside the instrument’s range (too low is prone to noise interference, too high may damage the lining).

3. Instrument wear or failure

• Electrode scaling, corrosion, or wear, leading to blocked or distorted signal transmission.
• Lining damage, aging, or deformation, changing the flow channel shape or affecting insulation performance.
• Failure of converter electronic components, such as damage to the amplifier circuit or excitation coil, affecting signal processing.

4. Parameter setting or environmental interference

• Parameters such as pipe diameter, range, and medium temperature/pressure are inconsistent with actual working conditions.
• Strong electromagnetic interference exists around (such as frequency converters, large motors), interfering with signal transmission.
• Zero calibration is not completed or has failed, especially if no recalibration is performed after long-term use.