Difference between Differential Pressure Flow Meter and Positive Displacement Flow Meter?

The difference between differential pressure flow meter and positive displacement flow meter is that, the former measures the change in the head due to changes in fluid density or viscosity while the latter measures flow rate by measuring how much liquid flows through a tube during the unit time.

What is  Pressure Flow Meter?

A positive displacement flow meter is a type of instrument that measures the volume of fluid passing through it as opposed to its density or specific gravity. this flow meter measures he flow of liquid in pipes. It measures the pressure drop in the pipe using an orifice, while it measures the flow of liquid by flowing through a constant-length section of pipe under test conditions. The liquid flows through a tube connected to an orifice at one end and the other end connected to a gauge. The gauge reads the amount of liquid flowing through it in cubic centimeters per second (cc/s).

The instrument is similar in principle to a differential pressure flow meter, but instead uses a cylinder filled with an inert gas such as helium and which holds mercury at one end and water at the other. By using this setup, it can be calibrated to calculate both volume and density accurately over a wide range of pressures and temperatures.

What is Differential Pressure Flow Meter?

A differential pressure flow meter is an instrument that measures the total volume of fluid passing through it. A differential pressure flow meter does not measure the total volume but rather the difference in pressure between two points. It has two sensors, which are connected to the pipeline by means of pipes and tubing. The instruments send signals to a control unit, which converts them into digital form and displays it on a screen. A pump or motor can be used to move fluid through the instrument, thus determining the rate at which fluid is flowing through it. Positive displacement flow meters measure changes in total head (the sum of the head loss and friction losses) and not just pressure differences between two points.

Difference between Differential Pressure Flow Meter and Positive Displacement Flow Meter?

1. Differential pressure flow meter measures the differential pressure in the flow of fluid between two sections.
2. Positive displacement flow meter is a type of volumetric flowmeter that uses positive displacement principles.
3. Pressure Flow Meter is easy to operate and use.
4.  Pressure Flow Meter can be operated manually or automatically.
5.  Pressure Flow Meter is Simple structure and design allow for easy installation, operation, repair and maintenance.
6. Pressure Flow Meter can be easily calibrated. It also measures accurately at any time and place without any trouble. The sensors used in this type of instrument are durable and provide accurate readings for long periods of time.
7.  Pressure Flow Meter Low cost
8.   Pressure Flow Meter is a Simple calibration method with few components only
9.   Due to the Compact design of  Pressure Flow Meter that is suitable for installation on high-pressure pipelines.
10. A Positive Displacement Flow Meter (PDFM) is a type of flow meter that measures the total volume of fluid passing through it.
11. Positive Displacement Flow Meter does not use moving parts or seals.
12. Positive displacement flow meters is their simple construction and accurate operation.
13. Positive displacement flow meters have been designed for use over extended periods without maintenance or replacement parts because they do not require lubrication or seal maintenance.
14. positive displacement flow meters offer higher accuracy over a wider range of pressures and temperatures
15. The positive displacement flow meter is a type of flowmeter which has the advantage of being able to measure accurately both positive and negative displacements.
16. Positive device are that it is quite expensive to buy, requires maintenance for accurate measurements and only measures the flow in liquids.
17. Positive displacement flow meter  can be damaged easily due to their construction materials being delicate so proper maintenance needs to be maintained at all times.
18. Pressure flow instrument is that it needs calibration every time before using it for measuring the flow rate which could take up a lot of time and effort as well as cost you money if you don't have an accurate set-up for this type of instrument.