How does a Micro Motion flow meter work?

Flow Q&A

I've seen a Micro Motion flow meter in my plant, but I don't know how it works. Can you give me more context on that?

Expert’s answer

Sure can. You may not know it, but you have a pretty impressive little device there. The Micro Motion flow meter comes from Emerson Automation Solutions, and this brand put the first Coriolis flow meter on the market. Now, you can find a bunch of vendors with similar tech, but Emerson did it first.

As the name denotes, the Micro Motion uses the Coriolis effect to measure. Coriolis meters provide some of the most accurate measurement on the market. They can measure flow and density, and you can find patented technologies on some devices that measure viscosity as well. We have a definitive guide to Coriolis meters here at Visaya, if you want to check out our in-depth discussion about this type of flow meter.

micro motion coriolis
Courtesy of Emerson
Working principle

The measuring tube comes in a variety of shapes, and vendors have sales pitches for each of them. So you’ll have to decide for yourself which suits your purposes best. The most common is the omega or “U” sensor.

Whatever the shape, the tube has a drive coil to vibrate the tube at a specific frequency. And at the inlet and outlet ends of the tube, you find pickoffs measuring this frequency.

If you don’t have flow, then both pickoffs vibrate at the same frequency, creating identical waveforms. When you have flow, it creates the Coriolis effect, a small twist that phase-shifts the waveforms from the pickoffs. Thus by measuring the amount of shift, you can calculate the mass flow rate.

And as for density, you’ll use the natural change of frequency that occurs in a change of fluid density. High density makes the frequency decrease, and low makes it increase. So you can use these changes to find the density of the product with great accuracy.

You can learn more about how a Coriolis flow meter works by watching this video:

Related tags: Basic Coriolis Coriolis flow meter devices Emerson Automation Solutions English Flow flow measurement Mass flow Measurement Micro Motion Principle
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