The electromagnetic flowmeter measures the liquid volume flow according to the Faraday electromagnetic induction principle, especially in the hygiene and food industries, it can meet the requirements of safety and hygiene. The sanitary electromagnetic flowmeter has the following advantages:
1. Simple structure, no moving parts, disturbance or throttling parts that hinder the flow of the measured medium, no pressure loss, no pipeline blockage, wear and other problems, so the sensor has a very long life.
2. It can measure the liquid-solid two-phase flow of ore pulp and sewage containing solid particles.
3. Electromagnetic flowmeter is an instrument that measures volume flow, and its measurement is not affected by changes in fluid density, temperature, pressure, viscosity, and electrical conductivity within a certain range. The electromagnetic flow meter only needs to be calibrated with water as the test medium, and other conductive liquids can be measured with meters without additional correction. This is an advantage that other flow meters do not have.
4. The electromagnetic flowmeter has a large measuring range. For the same caliber sensor, the full-scale flow velocity can be arbitrarily set within the range of 3-15m.
The measurement range of the electromagnetic flowmeter can cover the two velocity distribution states of turbulent flow and laminar flow, which is incomparable with the differential pressure flowmeter, turbine type, vortex flowmeter and other flowmeters.
5. In principle, the output signal has a linear relationship with the flow rate, the measurement accuracy is high, and the complete electrical signal output, the measurement reflection speed is fast, the pulsating flow rate and the rapid accumulation total can be measured.
6. In the sensor part, only the inner village and the electrode are in contact with the liquid to be measured. As long as the material of the electrode and inner village is selected reasonably, it can be corroded and resistant to wear.
7. In principle, it is to measure the average flow rate of the water section passing through the halo. The signal is integrated according to the weight distribution, and the requirements for the flow rate distribution are lower. Therefore, the straight pipe section before and after the sensor is required to be shorter than other flow meters. The length of the inlet is measured from the electrode axis. It is 5 times the pipe diameter, and the outlet length is 2 times the pipe diameter.
8. It can measure the flowing fluid in both positive and negative directions.
Of course, electromagnetic flowmeters also have many shortcomings. The important thing is to make full use of advantages and avoid disadvantages in the process of measuring flow. The main shortcomings are:
1. Electromagnetic flowmeter cannot be used to measure gas, steam and liquid containing a large amount of gas.
2. At present, electromagnetic flowmeter cannot be used to measure liquid medium with very low conductivity. The conductivity of the measured liquid medium cannot be lower than 10us/cm, which is equivalent to the conductivity of distilled water. It is still powerless to petroleum products or organic solvents.
3. Due to the temperature limitation of the insulating material of the measuring tube, the current industrial electromagnetic flowmeter cannot measure high temperature and high pressure fluids.
4. The electromagnetic flowmeter is affected by the flow velocity distribution. Under the condition of axisymmetric distribution, the flow signal is proportional to the average flow velocity. Therefore, there must be a certain length of straight pipe sections before and after the electromagnetic flowmeter.
5. Electromagnetic flow meter are easily affected by external electromagnetic interference.
For the measurement of milk, the advantages of electromagnetic flowmeters can be fully utilized and their disadvantages can be avoided. Moreover, the conductivity of the fluid such as milk is 200~300s/cm, which is far greater than the electromagnetic flowmeter's requirement for fluid conductivity greater than 10us/cm. In addition, the electromagnetic flow sensor has a simple structure, no moving parts, and does not hinder the fluid flow. It has a wide range and no Mechanical inertia is sensitive, so we choose electromagnetic flowmeter to measure milk.