Grounding method of electromagnetic flowmeter
Release time:
2021-08-06
Grounding method of electromagnetic flowmeter
We all know that the electromagnetic flow meter should be grounded when used and installed. Why?
Electromagnetic flowmeter is a flowmeter based on Faraday electromagnetic induction principle. The medium must be conductive medium. When the electromagnetic flowmeter works, its induced electromotive force is often in milliampere, and the signal voltage is very small. Therefore, in order to better and accurately measure these weak voltage signals and eliminate other interference signals, the electromagnetic flowmeter must be grounded.
(1) The installation pipe is metal pipe without internal coating.
At this time, as long as the metal pipe is connected with the electromagnetic flowmeter during installation, and the grounding wire is connected to the grounding grid.
(2) When installed in plastic or internally coated pipes, there are three grounding methods to choose from.
Use grounding ring
The grounding ring, also known as the liquid receiving ring, is used to stably and reliably connect the conductive liquid as the reference point of the differential potential signal with the signal of the converter, and form a similar or roughly equal potential with the liquid. There are three types:
Common grounding ring: similar to an orifice plate with handle
Protective grounding ring: it can protect the flange lining from damage
Neck type grounding ring: suitable for strong wear medium and can protect lining.
Because the grounding ring is directly in contact with the measuring liquid like the electrode, the material of the grounding ring is the same or similar to that of the electrode of the electromagnetic flowmeter.
Electrode grounding
In the selection of electromagnetic flowmeter, the selection of electrode material is directly and closely related to the corrosivity and wear of medium. When measuring highly corrosive medium, the electrode is generally made of precious heavy metals such as titanium (TI), tantalum (TA), platinum (PT), etc. through the above description, we know that the material of grounding ring is similar or consistent with that of electrode, Therefore, if the precious metal is used as the grounding ring in this case, it will greatly increase the cost of using electromagnetic flowmeter, which is not economical and feasible. In order to better realize the economy of electromagnetic flowmeter, the electromagnetic flowmeter with electrode grounding came into being. This electromagnetic flowmeter is different from the traditional electromagnetic flowmeter in that a third electrode with the same material and size as the measuring electrode is added at the lowest point where the sensor measuring tube is perpendicular to the measuring electrode for grounding.
Virtual grounding
With the development of electromagnetic flowmeter technology, the new technology virtual grounding is gradually applied to electromagnetic flowmeter
By providing isolation between the flow converter input amplifier and the optocoupler in the circuit, the potential of the measuring circuit in the liquid floats. Only when flowing through the flow sensor, the flow rate of the conductive liquid generates an induced voltage. The special signal processing of this converter allows the flowmeter sensor to be grounded to meet its normal operation and simplifies the installation process.
The electromagnetic flowmeter is widely used, reliable and stable, and occupies an important position in flow measurement. Grounding is to obtain the measured value more accurately, improve the accuracy and make the electromagnetic flowmeter work stably and reliably. After understanding the grounding mode of the electromagnetic flowmeter, we should fully consider the selection of grounding scheme when selecting the electromagnetic flowmeter, So that the electromagnetic flowmeter can give full play to its advantages.
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