Search:

How Do Flow Meters Work - Mass And Volumetric Flow Rates

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.

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 in an example of the principle determining the name. The Coriolis effect is the force that a liquid experiences in a circular motion. In the flow meter, vibrating pipes cause the liquid to move in a circular motion. If the wave motion of the vibrating pipes is known before the liquid passes through the pipes then the flow rate of the liquid can be determined.

The ultrasonic flow meter and Doppler shift flow meter also use wave mechanics to determine the flow rate of the medium passing through a pipe or tube.

In the case of the ultrasonic flow meter, two transmitters of ultrasonic sound waves are placed at the ends of a pipe where the measure is to take place. Each transmitter sends a pulse of sound.

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.

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 meters use a sound wave that bounces off matter in the medium passing through the pipe. Due to the Doppler effect, the frequency of the waves changes when it strikes a moving object. This change in the frequency can be used to determine the flow rate of the medium passing through the pipe.

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.