How Do Flow Meters Work - Flowmeter Types And Operation

by: AdrianFletcher
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Liquids and gases passing through a tube or pipe often need to be measured to determine the rate at which they are moving. They are generally measured in terms of their volume or their mass. A volumetric flow rate reading is meters to the power of three divided by time. The mass flow rate is kg's divided by time.

There is a diverse range of uses for flow meters. They have applications for individuals, a common one being to help people with asthma. A peak flow meter measures the lung capacity when someone exhales. This can help to predict an imminent asthma attack.

However the most varied applications are in the manufacturing industries or water management processes where precise measurements are vital for successful operations. This article will touch on how flow meters work in industry and for individuals.

There are a wide variety of types of flow meters. They are generally classified by what they do or how they operate. For instance, a mass flow meter is a general classification of flow meter that determines the flow rate of a medium in terms of mass even though the operating principles for each meter may be different.

The Coriolis flow meter is a point in case of a principle giving it's name to the type of flow meter. The Coriolis effect is the force exerted on a liquid moving in a circular motion. In the flow meter this is done by vibrating the pipes that the liquid passes through. The vibrations (or waves) that are created in the pipes are changed when the liquid passes through them. By knowing the changes in the wave vibrations you can work out the flow rate of the liquid.

Ultrasonic and Doppler shift flow meters also use the changes caused to sound waves to correlate a rate of flow for the medium passing through the meter.

The ultrasonic flow meter transmits two ultrasonic waves in opposite directions of a pipe where a liquid or gas is flowing.

Receivers at opposite ends of the pipe record the sound waves. One pulse of ultrasonic wave is sent off in the direction of the flow while the other is in the opposite direction.

Provided some information is known about the type of pipe used and a few constants for the liquid or gas, then the flow rate can be determined from the time difference of each wave.

Doppler shift flow meters also use waves to determine the flow rate. They work on the principle that a sound wave that bounces off a moving particle in the medium has it's frequency and amplitude changed. By determining the change in these dimensions, the flow rate of the medium can be determined.

A more traditional type of flow meter is the variable area flow meter that uses a float in a calibrated tube. When a substance passes through the tube, the float is displaced by the flow.

The float indicates a measurement on the calibrated tube. This is a correlation of the flow rate of the substance that has just passed through the tube. An example of such a device is the peak flow meter that is used to measure lung capacity. Peak flow meters help people with asthma determine if they are likely to have an asthma attack.