How Positive Displacement Flow Meters Work
|
How Positive Displacement Flow Meters Work Positive displacement flow meter technology is the only flow measurement technology that directly measures the volume of the fluid passing through the flowmeter. Positive displacement flow meters achieve this by repeatedly entrapping fluid in order to measure its flow. This process can be thought of as repeatedly filling a bucket with fluid before dumping the contents downstream. The number of times that the bucket is filled and emptied is indicative of the flow through the flow meter. Many positive displacement flow meter geometries are available. Entrapment is usually accomplished using rotating parts that form moving seals between each other and/or the flow meter body. In most designs, the rotating parts have tight tolerances so these seals can prevent fluid from going through the flow meter without being measured (slippage). In some positive displacement flow meter designs, bearings are used to support the rotating parts. Rotation can be sensed mechanically or by detecting the movement of a rotating part. When more fluid is flowing, the rotating parts turn proportionally faster. The transmitter processes the signal generated by the rotation to determine the flow of the fluid. Some positive displacement flow meters have mechanical registers that show the total flow on a local display. Other positive displacement flow meters output pulses that can be used by a secondary electronic device to determine the flow rate. |