Are there any measurement limitations for electromagnetic flow meters?
Jiang Hai De Gao
Release time：
2025-06-19
There are indeed some measurement limitations, mainly in the following aspects:
1. Conductivity of the measured medium
Electromagnetic flow meters can only measure the flow rate of conductive liquids. The conductivity of the fluid to be measured must be greater than 5μS/cm. Electromagnetic flow meters cannot measure liquids with extremely low conductivity (such as petroleum products, organic solvents, pure water, etc.) as well as gases and steam.
2. Flow rate range limitation
The measurement flow rate range of electromagnetic flow meters is usually between 0.5m/s and 10m/s. The measurement range of some small-diameter electromagnetic flow meters is 0.01m/s to 0.5m/s. When the flow rate is below 0.1m/s, the measurement accuracy may not be guaranteed.
3. Influence of medium characteristics
Temperature and pressure: The operating temperature range of electromagnetic flow meters is generally -20℃ to 180℃, and the operating pressure range is 0.6MPa to 42MPa. For high-temperature or high-pressure fluids, appropriate lining materials and pressure resistance levels must be selected.
Corrosiveness and abrasiveness: If the medium to be measured is corrosive or abrasive, corrosion-resistant and wear-resistant electrodes and lining materials must be selected.
4. Installation condition limitations
Straight pipe section requirements: Although electromagnetic flow meters have relatively low requirements for straight pipe sections, certain conditions must still be met to ensure measurement accuracy.
Full pipe requirement: The fluid to be measured must fill the pipe, otherwise it may cause measurement errors or the instrument may not work properly.
Installation location: Avoid installation in areas with strong electromagnetic interference, and the sensor should have good grounding.
5. Electrode pollution problem
The electrodes of the electromagnetic flow meter are in long-term contact with the liquid and are easily polluted or scaled, thereby affecting the measurement accuracy. For media that are prone to scaling, the electrodes need to be cleaned regularly.
6. Span ratio limitation
Although the span ratio of electromagnetic flow meters can reach 1:100 or even higher, in practical applications, the appropriate diameter should still be selected according to the actual flow range to ensure measurement accuracy.
In summary, electromagnetic flow meters have certain limitations in the conductivity of the measured medium, flow rate range, medium characteristics, and installation conditions, and reasonable selection and installation should be carried out according to the specific application scenario.
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