| Flow meters are devices that are used to measure | | | | Ultrasonic and Doppler shift flow meters also use the |
| the flow rate of a certain liquid or gas. They can | | | | changes caused to sound waves to correlate a rate |
| measure these substances in terms of the volumetric | | | | of flow for the medium passing through the meter. |
| flow rate or the mass flow rate. The volumetric flow | | | | In the case of the ultrasonic flow meter, two |
| rate is generally given in m3/second. The mass flow | | | | transmitters of ultrasonic sound waves are placed at |
| rate is given in kg/second. Flow meters have many | | | | the ends of a pipe where the measure is to take |
| applications. For individuals, a peak flow meter can | | | | place. Each transmitter sends a pulse of sound. |
| measure the lung capacity. This is also used by | | | | The transmitters also act as a receiver of the wave |
| people with asthma and can be used to determine if | | | | sent by the other transmitter. One pulse of sound is |
| an asthma attack is imminent. Other than that, flow | | | | sent in the direction of the flow of the liquid and the |
| meters are used in many industries, like the food | | | | other is sent against the flow. If various constants |
| processing industry, water management, semi | | | | are known about the metal of the pipe and the liquid |
| conductor fabrication and many others. This article will | | | | or gas passing through the pipe, a rate of flow can |
| give a brief overview of how flow meters work. | | | | be derived from the time it takes each sound wave |
| Flow meters are generally classified by the principal | | | | to reach the receiver. |
| that governs their operation or possibly by their | | | | Doppler shift flow meters use the changes in the |
| applications. For instance, mass flow meters measure | | | | frequency and amplitude of a sound wave when it |
| the flow rate of a medium in terms of it's mass. | | | | bounces off particulate matter in the liquid that is |
| However, there are types of mass flowmeters that | | | | being measured to determine the flow rate. |
| use different methods to take this measurement. | | | | A more traditional type of flow meter is the variable |
| One example of this is the Coriolis flow meter that | | | | area flow meter that uses a float in a calibrated tube. |
| uses the Coriolis effect to determine the mass of a | | | | When a substance passes through the tube, the |
| fluid passing through two vibrating tubes or pipes. | | | | float is displaced by the flow. By taking the reading |
| The idea being that by understanding the change in | | | | from the calibrated tube an indication of the flow |
| the characteristics of the wave patterns in the | | | | rate can be determined. This is the principle of the |
| vibrating tubes, you can correlate the flow rate of | | | | peak flow meter used for lung capacity and asthma. |
| the substance passing through. | | | | |