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hi all,
Can some one tell me how a electromagnetic flow meter gives readings in kgs/min?It should give volumetric flow rate .How can it give the mass flow rate when the density of the liquid which is flowing through it is different at different applications.




Gautam

[Art Montemayor]

Gatty:

From what I know about an electomagnetic flow meter, the readout is usually given in average fluid velocity. This velocity can be related to the cross-sectional flow area of the pipe it is measured in and yield volumetric flow rate. This same volumetric flow rate can also be translated to mass flow rate if you know the fluid's density at that measured point. The following is a formal definition of the flow meter and how it works:

The electromagnetic flowmeter is similar in principle to the generator. The rotor of the generator is replaced by a pipe placed between the poles of a magnet so that the flow of the fluid in the pipe is normal to the magnetic field. As the fluid flows through this magnetic field, an electromotive force is induced in it that will be mutually normal (perpendicular) to both the magnetic field and the motion of the fluid. This electromotive force may be measured with the aid of electrodes attached to the pipe and connected to a galvanometer or an equivalent. For a given magnetic field, the induced voltage will be proportional to the average velocity of the fluid. However, the fluid should have some degree of electrical conductivity.

I don't understand your question the way it is presented: "Can some one tell me how a electromagnetic flow meter gives readings in kgs/min?" Do you mean to say that you have a meter that is reading out mass velocity? Or have you simply been told that? What are the facts and circumstances behind your query?

If the meter is applied on a single fluid flow piping application, I can see where someone could calibrate it to read out in mass velocity. Why they would do that is something I can't explain. Normally you desire a volumetric flow rate. However mass flowrates are also of interest in some applications.

You state that the density of the liquid flowing through it is different at different applications. Under these circumstances, I would question the calibration of the meter. Or perhaps the calibration is changed when the fluids are changed. We can't expound on how it operates; you haven't given us all the basic data. All I can give you is the above general explanation. Since you haven't furnished specific information that is all you can expect to receive from your query.