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electromagnetic flowmeters

2020-07-02
 The Main Influencing Factors of Electromagnetic Flowmeters That are Prone to Errors During Daily Use
 
1. The measured liquid flow rate
The flow velocity range that can be measured by electromagnetic flowmeter is generally 0.5～10m/s, 
and the economic flow velocity range is 1.5～3m/s. In actual use, the inner diameter of the measuring 
tube should be determined according to the size of the flow to be measured and the range of the flow 
rate that can be measured by the electromagnetic flowmeter.
 
2. Selection of electrode and lining materials
The electrode and lining material are in direct contact with the liquid to be measured, and the electrode 
and lining material should be selected according to the characteristics of the liquid to be measured 
(such as corrosiveness, abrasiveness, etc.) and working temperature.If not selected properly, it will 
cause fast attachment speed, corrosion, and junction. Problems such as scale, wear, and deformation of the lining, 
which in turn produce measurement errors.
 
3. Electromagnetic stability
The excitation methods of the electromagnetic flowmeter include DC excitation, AC sine wave excitation 
and dual-frequency rectangular wave excitation, etc.DC excitation is prone to electrode polarization and 
DC interference problems, AC sinusoidal excitation is easy to cause zero point change, while dual-frequency 
rectangular wave excitation Low-frequency rectangular wave excitation has excellent zero-point stability,
It also has a strong ability to suppress high-frequency rectangular wave excitation of fluid noise, which 
is an ideal excitation method. In practical applications, the stability of the power supply voltage and 
frequency should be ensured as much as possible to ensure the constant magnetic field strength and reduce 
the measurement error caused by the change of the magnetic field strength.
 
4. Mixed phase fluid measurement
When measuring the flow rate of liquid-solid mixed-phase fluid (such as water containing sediment) with an 
electromagnetic flowmeter, if an electromagnetic flowmeter calibrated by a single-phase liquid is used, 
a measurement error will occur. In this case, it should be selected not to cause a liquid-solid phase Install 
the sensor at the separated straight pipe section.

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