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How Do Flow Meters Work


									How Do Flow Meters Work
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. Other than
that, flow meters are used in many industries, like the food processing
industry, water management, semi conductor fabrication and many others.
This article will give a brief overview of how flow meters work.
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.
However, there are types of mass flowmeters that use different methods to
take this measurement. One example of this is the Coriolis flow meter
that 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. 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.
The transmitters also act as a receiver of the wave sent by the other
transmitter. One pulse of sound is sent in the direction of the flow of
the liquid and the other is sent against 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 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. By taking the reading from
the calibrated tube an indication of the flow rate can be determined.
This is the principle of the peak flow meter used for lung capacity and
Find out more about how flowmeters work and the various types of flow
meters available at Adrian Whittle writes
about the use of flow meters for personal use and in industry.

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