|Item comparison||Electromagnetic Flowmeter||Ultrasonic Flow Meter|
|working principle||Faraday’s law of electromagnetic induction||Time difference between forward and reverse flow of ultrasonic waves|
|measurable range||Liquid with conductivity ≥5uS/cm||Liquid, gas and steam can be measured|
|installation method||Tube type/plug-in type||Pipe section/plug-in/clamp-on|
|installation conditions||Closure installation||Installation under pressure|
|measurement method||Electromagnetic induction||time difference method|
|Pipeline versatility||very poor||unlimited|
|maintenance method||more difficult||simple|
|Application field||mainly storage tanks||Mainly water pipes|
1. The working principle is different.
Electromagnetic flowmeters are flowmeters that measure flow according to Faraday’s law of electromagnetic induction.
Ultrasonic flowmeters measure the flow rate based on the time difference between the forward and reverse flow of the ultrasonic beam in the pipeline.
2. The measurable range is different.
Electromagnetic flowmeters have requirements for the lower limit of the conductivity of the measured liquid. Generally, the conductivity of the measured medium is not lower than 5uS/cm.
Compared with the electromagnetic flowmeter, the ultrasonic flowmeter has a relatively large measurement range. It can measure the gas and steam that the electromagnetic flowmeter cannot measure. Non-conductive, radioactive, and flammable and explosive media can also be measured with high precision.
3. The installation method is different.
Most of the electromagnetic flowmeters are installed in the pipe section, and a small part is installed in the plug-in type. Both of these installation methods require cutting or digging holes in the pipeline, and the pipeline as a whole needs to be closed and shut down before installation.
Ultrasonic flowmeters generally have three installation methods: clamp-on type, plug-in type and pipe-section type. The commonly used two types are clamp-on type and plug-in type, and there is no need to stop the installation for installation. Among them, the external clamping installation will not damage the pipeline, will not contact with the measured medium, and has no possibility of leakage.
4. The installation conditions are different.
Electromagnetic flowmeters are generally shut-off installations.
Ultrasonic flow meters are installed under pressure.
5. Pipe diameter versatility varies greatly.
Electromagnetic flowmeters are generally used for a specific pipeline, because factors such as the size of the pipe diameter and the measured medium in the pipe will affect the pipe section size and lining of the electromagnetic flowmeter, so the general versatility of the electromagnetic flowmeter is relatively poor.
The ultrasonic flowmeter adopts external clamping and plug-in installation, so there is no problem in this aspect. It can be used in different pipe diameters and different measured media, and the versatility is relatively good.
6. The maintenance inspection cycle is different.
The verification cycle of the electromagnetic flowmeter is once every two years.
The verification cycle of ultrasonic flowmeter is once every three years.
7. Check that the maintenance items are different.
The electromagnetic flowmeter needs to check whether the external equipment is infiltrated with water or other substances, whether there is an increase of electromagnetic field equipment nearby or wires across the meter, all of which will affect the measurement of the electromagnetic flowmeter.
Ultrasonic flowmeters are much more convenient. For maintenance, you only need to check whether the SQ value displayed by the flowmeter, the sound velocity ratio and other parameters are good. If there is a problem with the values, you can check whether there are foreign objects or looseness at the sensor position.
8. Different fields of application.
Electromagnetic flowmeters mainly use electromagnetic waves for measurement. Electromagnetic waves have the characteristics of high frequency and small attenuation. The measurement range of the waveguide is also relatively large. Therefore, it is mostly used for storage tanks. The caliber of electromagnetic flowmeters can be above DN2000.
Ultrasonic flowmeters mainly use sound waves for measurement. The frequency of sound waves is low, the measurement unit is small, and the application area is relatively narrow. In the flow measurement of large-diameter water pipelines, pipe-type ultrasonic flowmeters rarely have a caliber above DN800.