How Do Flow Meters Work - Flowmeter Types And Operation

By: Adrianfletcher
Flow meters are devices that are used to measure the flow rate of a certain liquid or gas. They can measure these substances in terms of the volumetric flow rate or the mass flow rate. The volumetric flow rate is generally given in m3/second. The mass flow rate is given in kg/second.

Flow meters have many applications. For individuals, a peak flow meter can measure the lung capacity. This is also used by people with asthma and can be used to determine if an asthma attack is imminent.

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.

Flow meters are generally classified by the principal that governs their operation or possibly by their applications. For instance, mass flow meters measure the flow rate of a medium in terms of it's mass.

One example of a principle governing the name of a meter is the Coriolis flow meter. It uses the Coriolis effect to determine the mass of a fluid passing through two vibrating tubes or pipes. The idea being that by understanding the change in the characteristics of the wave patterns in the vibrating tubes, you can correlate the flow rate of the substance passing through.

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.

For an ultrasonic flow meter, flow rate is measured by contrasting the measurements of two ultrasonic waves. These two waves are set off at the same time as each other but from different directions.

The ultrasonic waves are recorded by receivers at opposite ends of the pipe. One wave is sent in the direction of the flow of the liquid to be measured. The other wave is sent in the opposite direction to the flow.

If various constants are known about the metal of the pipe and the liquid or gas passing through the pipe, a rate of flow can be derived from the time it takes each sound wave to reach the receiver.

Doppler shift flow meters use the changes in the frequency and amplitude of a sound wave when it bounces off particulate matter in the liquid that is being measured to determine the flow rate.

A variable area flow meter is a more standard type of meter. It uses a float that is moved by the force of the substance passing through a calibrated tube.

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.
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