In case you haven't noticed, there are several types of flow meters and flow sensors. There are also a number of different operating principles. Have you ever wondered if there were other, more efficient methods than what you are currently using? If you have, you're in luck. We've compiled a list of 8 different flow meter types and operating principles as well as pros and cons for each. Let's take a look at the first 4...
Electromagnetic flow meters detect flow by using Faraday's Law of induction. Inside an electromagnetic flow meter, there is an electromagnetic coil that generates a magnetic field, and electrodes that capture electromotive force (voltage). Due to this, although it may appear as if there is nothing inside the flow pipe of an electromagnetic flow meter, flow can be measured.
Classified as a vortex flow meter, this device utilizes a law that was theoretically proven by Theodore von Karman in 1912. When there is a column-shaped obstruction (vortex shedder) in flowing fluid, it will generate alternating vortices downstream. The flow velocity of the fluid and the vortex generation frequency are proportional to each other. Therefore, detecting the number or pulse of vortices makes it possible to measure flow. The main method of detection involves sensing the vortex vibration with a piezo element. However, a more robust method utilizes ultrasonic waves to detect the vortex vibration.
STRUCTURAL DIAGRAM OF A KARMAN VORMAN VORTEX FLOW METER
This is classified as a turbine flow meter. Paddle wheel flow meters are generally divided into two mechanical classes as described below:
(1) Tangential-flow paddle wheel flow meters, with a water wheel structure
(2) Axis-flow paddle wheel flow meters, with a windmill structure
The flow and the revolutions of the paddle wheel are proportional to each other. Thus, by spinning the paddle wheel with the force from the flowing fluid, it becomes possible to measure the rate of this flow from the number of revolutions. By embedding a magnet in the rotation axis and on the edge of the paddle, pulses can be extracted as signals, converting the number of revolutions into the flow rate.
STRUCTURAL DIAGRAM OF A PADDLE WHEEL FLOW METER
This is classified as an area flow meter. Its mainstream method involves suspending a float in a tapered pipe (a pipe that progressively widens heading upwards). When the fluid is forced in between the tapered pipe and the float, a differential pressure is generated. When this happens, the float stops at an area where the upward force caused by differential pressure and the downward force caused by the weight of the float have been equalized. The resulting display is the instantaneous flow. Commonly, the tapered pipe is manufactured from transparent materials calibrated for flow and measurements are read directly from the pipe. There are also types available that have a magnet built into the float and perform detection using a magnetic sensor.
FLOATING ELEMENT FLOW METER
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