The function of the grounding wire of the electromagnetic flowmeter is mainly to reduce the influence of electromagnetic interference on the measurement accuracy, improve the anti-interference ability of the instrument, and ensure the stable operation of the sensor.
First of all, the electromagnetic flowmeter uses the principle of electromagnetic induction to measure the flow rate of the fluid, so it is susceptible to external electromagnetic interference. The grounding wire can direct electromagnetic interference to the ground, reducing its impact on measurement accuracy.
Secondly, the sensor output signal of an electromagnetic flowmeter is usually only a few millivolts, which is very weak. In order to improve the immunity of the instrument, the zero potential in the input circuit must be zero at the ground potential. The ground wire ensures zero-potential alignment, which is necessary to ensure the stable operation of the sensor. If there is a poor grounding or no grounding wire, it will cause an external interference signal to affect the AD converter sampling, and there may be empty pipes or report errors in the form of zero or negative signals.
Thirdly, the grounding point of the sensor output signal should be electrically connected with the measured medium, which is a necessary condition for the operation of the electromagnetic flowmeter. When a fluid cuts a magnetic wire to produce a flow signal, the fluid itself acts as a zero potential, with one electrode producing a positive potential and the other generating a negative potential, and constantly alternating. Therefore, the midpoint of the converter input (the signal cable shield) must be at zero potential with the fluid and turn on to form a symmetrical input circuit. The midpoint of the converter input is electrically connected to the fluid under test through the grounding point of the sensor output signal.
Finally, for the case where the ground potential is used as the reference potential, the general metal pipe is connected to the ground, and the flowing medium is electrically connected to the ground through the metal pipe, which can usually meet the grounding requirements. The metal process pipe is in direct contact with the medium, and the grounding wire is also directly connected to the metal pipe or flange, so there is no need for additional grounding rings.