There are an array of instruments or devices which are used to measure the flow of liquids and gases. Some of the measuring instruments can also be used to control the flow of steam and gases. In most of the industrial plants, it is essential to measure the flow of liquids. The flow rate in the devices is often determined by the change in kinetic energy or the liquid velocity.
The primary devices are basically classified into two types which include the flumes and the weirs. It is essential to choose these devices according to the minimum and maximum flow rate expected in a particular area. Weirs are made of aluminum or fiberglass and it is often built across an open channel like a dam. The liquid flows through an opening. It is one of the most widely used measuring devices as it is simple in structure and easy to maintain. It is also less expensive compared to the other types of devices.
Flume is another primary device which alters the channel area with its channel restrictions. This simple alteration increases the level and the velocity of the fluid.
The secondary devices are mainly used to measure the variations in the fluid level. The different types of secondary measuring devices include the floats and the capacitance probe. The capacitance probe is a device which determines the variations in the liquid according to the electrical conductivity.
Floats are among the most commonly used secondary devices as it is easily available and affordable. However, today there are more accurate devices such as the ultrasonic sensors which can be used to measure the flow of liquid accurately.
Velocity Flow Meters: It is mainly used to measure the speed of the flow in various areas of a system. Various types of velocity flow meters are used to measure the flow in household applications such as air conditioning systems, heating and ventilation systems.
Mass Flow Meter: These meters can be used to measure the mass flow without using any type of obstruction in the flow path. These meters are available in two forms which include the coriolis and the thermal flow meter.
Positive Displacement Flow Meter: These flow meters use rotors to measure the flow of liquid. It includes high precision. The rotors turn due to the flow of the liquid. The flow is measured by calculating the speed of the rotors and the amount of liquid made to pass in each turn of the rotor. Some of the modern devices use electrical signals to indicate the speed of the rotors.
Differential Pressure Flow Meters: This device calculates the flow according to the pressure drop of the liquid which passes through the obstruction that is inserted into the flow. It is mostly accurate for high pressure systems. Most of the industries use flow nozzles to measure the flow of air and gases.
There are many reputed companies online which sell a wide range of measuring instruments at affordable prices.