A liquid flow sensor is a device used to measure the flow rate of a substance. It is also called a flow valve. It also measures the quantity of a moving liquid. They help in simplifying the process of fluid measurements. Most applications require accurate flow rates. Accurate liquid flow measurement needs can be met by using a sound wave liquid flow sensor. These have accurate sensing elements.

There are different types of valves that accurately gauge the flow rate. They include:

Differential pressure flow sensors

 In this type of flow sensors, the flow is calculated by gauging pressure drop over a hindrance fitted in the flow. It uses an equation. The common types of differential liquid flow sensors are

Orifice plates

Venturi Tube

Flow Nozzles

Variable area Rotometer

Orifice plates

This device measures liquid flow. The flow is measured through the difference in pressure from the upstream side to the downstream side. The pipe used in which the fluid passes through is partially obstructed. The plate causes an obstruction that narrows the pipe. When the pipe is narrowed, the fluid is forced to constrict. The plates are simple, cheap, and very accurate in measuring the flow of liquids.

Venturi Tube

This is a short tube with a constricted inner surface. It is used to measure fluid flows. It was discovered by Battista Venturi. He observed the effects of constricted channels and designed an instrument with a narrow throat in the middle. The fluid flow rate is gauged by reducing the cross-sectional flow area in the flow path. It then generates a pressure difference.

Flow Nozzles

They are suitable for use with high-velocity flows. They do not suffer the wear that occurs in orifice plate edges during such flows.

Variable area flowmeter

It consists of a vertically aligned glass tube. The glass tube has a larger end at the top. It also consists of a metering float. The float moves freely within the tube. The flow of liquid causes the float to rise in the tube as the upward pressure changes. 

Magnetic flow sensors

These flow sensors work on the principle of movement of a conductor. The conductor passes through a magnetic field. It induces a voltage. Magnetic flow sensors have a flow tube. The tube produces the magnetic field in the pipeline. They also have an electronic converter. It measures induced voltage. These meters are very accurate. 0.5% of the flow rate over a dynamic range up to 300:1. To maintain this accuracy, they must always have a flow rate of 1.5 fps.

Laser-Doppler flow sensors

These types of flow sensors are used to scan a flow field. This is necessary to achieve certain details. If a fluid is moving towards a sensor, the frequency of the signal will increase. As it goes away from the sensor, the frequency of the returning signal decreases. The difference in frequency is equal to the reflected frequency minus the originating frequency. It can be used to calculate the speed at which the liquid flows.

Calorimetric Flow sensors

The principle for fluid flow measurement is depended on two temperature sensors. These sensors are in close contact with the fluid. They have thermal insulation that separates them. One of the sensors is heated, and the cooling effect monitors the flow rate. When the liquid flow increases, heat energy is extracted from the heated sensor, and the temperature difference between the sensors is reduced. The loss is proportional to the flow rate of the fluid.

Positive Displacement flow meter

This is a common type of flow sensor. It measures fluid flow by using rotors. The rotation of the rotors is proportional to the volume of the fluid being displaced.
The frequency of turns of the rotor is counted by a pulse transmitter and converted to volume and flow rate. Each increase is related to a connecting register. This type of flow sensor is very accurate and most efficient for measuring the flow of viscous liquids.


Liquid flow measurement is important. It helps to meet the requirements in industrial settings. Failure to take accurate measurements can lead to disastrous results. To do accurate readings, a good choice of flow control valves should be one of the main considerations. They also help in detecting leakage rates. This is important because it helps reduce wastage. In terms of accuracy, the volumetric flow stays valid. This is only possible if the process conditions are well followed.

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