- Differential Pressure Flowmeters Differential pressure flowmeters use a mathematical equation to calculate flow based on the pressure drop of liquid passing through obstructions inserted into the flow. Variations of this type of flowmeter include orifice plate meters, which are most accurate for high-pressure systems; Venturi tubes, which provide better accuracy in low-pressure systems; and flow nozzles, which are used in industrial settings to measure the flow of gases and air.
- Velocity Flowmeters Velocity flowmeters measure the speed of the flow in one or more areas of the system. When that speed is calculated with the volume of the pipe through which it is flowing, it reads how much liquid is being moved in a given time. Variations of velocity flowmeters are used in many common household applications, such as heating, ventilation and air conditioning systems. The most complex types of velocity flowmeters are found in large industrial applications and use elements as diverse as electromagnetism and ultrasonic measuring tools.
- Positive Displacement Flowmeters Positive displacement flowmeters use rotors that are formed to high precision so as to measure flow. The flow causes the rotors to turn. The engineer knows how much liquid flow is required to make a full turn of the rotor. By calculating the speed of the rotors by how much liquid passes in each turn, the flow can be measured. Many modern positive displacement flowmeters use electronic signals to tell the observer how fast the rotors are turning.
- Mass Flowmeters Mass flowmeters measure the mass of the flow directly without setting any obstructions within the flow itself. They come in two primary forms, a thermal and a coriolis flowmeter. The thermal mass flowmeter uses a heated element and a mathematical formula to determine flow rate. The coriolis flowmeter sends fluids through a special U-shaped tube. The tubes deform and set up harmonic vibrations that an engineer can use to precisely calculate flow rate and volumes very accurately.
- Open Channel Flowmeters The open channel flowmeter is one of the simplest and most direct of the flow measuring devices. It measures flow by setting up an obstruction across the bottom of a system and measuring the height and velocity of the fluid as it passes over that obstruction. Open channel flowmeters are often used to measure the flow of streams and rivers, particularly those used in conjunction with water or sewer systems.
Flow Meter Tutorial
So you want to measure flow? The answer would seem to be to purchase a flowmeter. With fluid flow defined as the amount of fluid that travels past a given location, this would seem to be straightforward — any flowmeter would suffice. However, consider the following equation describing the flow of a fluid in a pipe.
Q = A x v
Q is flow rate, A is the crosssectional area of the pipe, and v is the average fluid velocity in the pipe.
