Electromagnetic flowmeter (EletromagneticFlowmeters, referred to asEMF) is a new type of flow measuring instrument 50~60 in twentieth Century with the development of electronic technology and the rapid development of the. Electromagnetic flowmeter is made according toFaraday's law of electromagnetic induction, used to measure thevolume flow of conducting liquid meter. Because of its unique advantages, flow measurement has been widely used in various industrial processes of conducting liquid, such as all kinds of acid,alkali, salt and other corrosive media; all kinds of slurry flow measurement, forming a unique application field.

In the structure, the electromagnetic flowmeter is composed of two parts: electromagnetic flow sensor and converter component. Sensor is installed in the industrial process piping, it is the role of the flowing liquid volume flow pipeline values within the linear transform into induced EMF signal, and the signal is sent to the converter through the transmission line. Converter is installed in the not too distant from the sensor place, it will amplify the flow sensor signal, and converted into a flow signalproportional to the standard electrical signal output, for display,accumulation and regulation control.

The main advantages of the electromagnetic flowmeter are as follows:

1) the structure of the sensor of electromagnetic flowmetermeasurement is simple, no moving parts inside the tube, no throttling component impede fluid flow. So when the fluid through the flow timedoes not cause any additional pressure loss, flow meters, is one of thelowest energy consumption in operation of the flowmeter.

2) can measure the dirty media, corrosive medium and suspended solid liquid two phase flow. This is because the meter measuring tube internalwithout obstructing the flow components, contact with the fluid to be measured is measuring pipe lining and electrode, the materials can beselected according to the characteristics of the measured fluid to. For example, using poly three vinyl fluoride or Teflon lined, can measure all kinds of acid, alkali, salt and other corrosive medium; the abrasion resistant rubber lining, particularly suitable for wear in the measurementwith solid particles, the larger cement slurry, liquid - solid two - phase flow and various with fiber and paper pulp suspension liquid the turbidliquid.

3) electromagnetic flowmeter is a kind of volume flow measurement instrument, in the process of measurement, it is not affected by temperature, viscosity, density of measured medium conductivity (in a certain range) effect. Therefore, just as water electromagnetic flowmeter calibration, will be used to measure other conductive liquid flow.

4) the output of the electromagnetic flowmeter is only proportional to theaverage flow velocity measured medium, and the symmetric distributionof flow state (laminar or turbulent) independent. So a very wide range of the electromagnetic flowmeter, the measurement range of up to 100:1,some even up to 1000:1 can be run flow range.

5) electromagnetic flowmeter without the mechanical inertia, sensitive reaction, can measure the instantaneous pulse flow, but also can measure the pros and cons of the two directions of traffic.

6) industrial electromagnetic flowmeter diameter scope very wide, from a few mm has been to several meters, and the domestic existingdiameter up to 3m real flow calibration equipment, has laid the foundation for the application and development of electromagnetic flowmeter.

The main problems of electromagnetic flowmeter still exists at presentare as follows.

1) cannot be used to measure the gas, steam and gas rich liquid.

2) cannot be used to measure the liquid medium very low conductivity,as of a petroleum product or organic solvent media, at presentelectromagnetic flowmeter is also incapable of action.

3) for general industrial use of electromagnetic flowmeter measurement due to pipe lining material and electrical insulating material constraints,can not be used for the measurement of high temperature medium;without special treatment, it can not be used for measuring low temperature medium, in order to prevent condensation (Frost) outside the measuring pipe insulation failure.

4) effect of electromagnetic flowmeter is susceptible to external electromagnetic interference.