What is the reason why the electromagnetic flowmeter is grounded?

Regarding the grounding of electromagnetic flowmeter, its share in automatic control knowledge system is very small. There are many people who can skillfully quote norms and use rules, but not many people can say that they are reasonable at once. This is actually out of a habit of thinking. After learning multiplication, we seldom care about the relationship between multiplication and addition, but we won't make mistakes because this knowledge point has already melted into the blood. However, the study of some professional knowledge often lacks the practice of cultivating conditioned reflex before the college entrance examination, so people often remember the conclusion and ignore the reasons.

When discussing grounding, first ask a question. What is grounding?

We usually talk about all kinds of grounding protection grounding, shielding grounding, working grounding, signal grounding and so on, all of which are functions that need to be realized through grounding. Discharge electromagnetic interference, lightning protection, personal safety protection, 

The essence of grounding is to establish equipotential based on the earth between various points of the circuit as needed. For example, when an electrical appliance leaks electricity, the potential at the leakage place can be forced to be equal to the position of the human body through grounding, and an equipotential is formed between the leakage place and the position of the human body, so that there is no current without potential difference and people will not get an electric shock. So there is a protective grounding that can protect personal safety; The interference of electromagnetic field to signal has a process of electro-magnetism, electro-magnetism and electro-regeneration.

Using metal shielding can weaken the transmission of interference, but it may not be satisfactory. Through grounding, the electricity formed by interference on the shielding layer is forced to the potential with zero signal to realize equipotential. Without the potential difference, interference can be regarded as nothing for the signal. So there is a shielded grounding that releases interference through grounding; If there is no unified reference point for the control signal, it will happen that the 1-5V emitted by instrument A is considered as 2-6V by instrument B. The solution to this problem is to provide a common reference point for all instruments. This has the instrument of working grounding; We plan the grounding, in fact, to plan those points that need to establish equipotential, how to connect them is beneficial to establish equipotential, and to coordinate the countermeasures and tolerance when the established equipotential deviates from the ground reference potential.

What should I do after the intelligent electromagnetic flowmeter is disturbed?

According to the characteristics of general intelligent electromagnetic flowmeter system, this paper mainly discusses the interference sources of electromagnetic flowmeter from the aspect of hardware optimization, such as electromagnetic coupling and electrostatic induction, which are the important sources of interference noise produced by intelligent electromagnetic flowmeter.

In the electromagnetic flow transmission, because the leads of the two electrodes are in an alternating magnetic field, when the transmission is electrified, the induced electromotive force is generated in the closed loop of the leads. This interference signal is superimposed on the measurement signal, which affects the operation of the system. Various excitation modes will bring different electromagnetic interference problems. DC excitation mode is easy to produce polarization interference, and AC excitation mode is easy to produce orthogonal interference (90-degree interference) and in-phase interference (that is, power frequency interference).

Orhogonal interference refers to the interference that is 90 degrees different from the flow signal in phase. When the intelligent electromagnetic flow transmitter adopts AC excitation mode, it will generate an alternating magnetic field, and the closed loop composed of electrode, lead wire, measured medium and input circuit of converter is in the interference alternating magnetic field, so the closed loop cannot be completely parallel to the magnetic field lines generated by the alternating magnetic field of the transmitter, and there will always be some alternating magnetic field lines passing through the closed loop, thus generating an interference electromotive force in the loop. In the electromagnetic flowmeter, measures are taken from the transmitter and converter to eliminate or suppress 90.

In-phase interference power frequency interference or common-mode interference of intelligent electromagnetic flowmeter refers to the interference signal that appears on the two electrodes of the transmitter at the same moment and has the same amplitude and phase. When the flow rate is zero, that is, when the measured liquid is stationary, the measured in-phase signal is the in-phase interference signal. Electromagnetic flowmeter has many methods to suppress in-phase interference. In the transmitter, the electrode and the excitation coil are balanced and symmetrical in geometry, size and performance parameters, and are strictly shielded respectively to reduce the influence of distributed capacitance between the electrode and the excitation coil.

Characteristics of electromagnetic flowmeter:

1. The measurement is not affected by the change of fluid density, viscosity, temperature, pressure and conductivity;

2. There is no obstruction of flow parts and pressure loss in the measuring tube, and the requirements for straight pipe section are low. It has unique adaptability to slurry measurement;

3. Reasonable selection of sensor lining and electrode materials means good corrosion resistance and wear resistance;

4. The converter adopts novel excitation mode, with low power consumption, stable zero point and high accuracy. The flow range can reach 150: 1;

5. The converter can be integrated with the sensor or separated;

6. The converter adopts a 16-bit high-performance microprocessor with 2x16LCD display, which is convenient for parameter setting and reliable for programming;

7. The flowmeter is a two-way measuring system with three totalizers: forward total, reverse total and difference total; It can display positive and negative flow, and has various outputs: current, pulse, digital communication, HART；;

8. The converter adopts surface mount technology (SMT), which has the functions of self-inspection and self-diagnosis;

9. The measurement accuracy is not affected by the changes of fluid density, viscosity, temperature, pressure and conductivity. The voltage signal induced by the sensor has a linear relationship with the average flow rate, so the measurement accuracy is high.

10. Measure the unobstructed parts in the pipeline, so there is no additional pressure loss; There are no moving parts in the measuring pipeline, so the service life of the sensor is extremely long.

11. Because the induced voltage signal is formed in the whole space filled with magnetic field, and it is the average value on the carrier surface of the pipeline, the straight pipe section required by the sensor is short, and the length is five times the diameter of the pipeline.

12. The converter adopts internationally advanced single chip microcomputer (MCU) and surface mount technology (SMT), with reliable performance, high precision, low power consumption, stable zero point and convenient parameter setting. Click on Chinese LCD to display cumulative flow, instantaneous flow, flow rate, flow percentage, etc.

13. Two-way measuring system can measure forward flow and reverse flow. Adopt special production technology and high-quality materials to ensure the stability of product performance for a long time

Link-B2B is a professional supplier listing service platform which will provide high quality and trustworthy supplier list to international buyers. If you are looking for electromagnetic flowmeter suppliers, feel free to visit Link-B2B.com and send a request.