What Are The Types of Flow Sensors and How Do They Work?

There are several types of flow sensors. Each of them plays a specific role in flow gauging. There are dozens of flow sensor types. But some are rare due to their limited uses. Thus, we will not check the rare types. Instead, we will deal with the common types of flow sensors and see how they work.

Many people use flow meters as flow sensors. It was made possible by technological advancement. Also, some flow meters are made with inbuilt sensors. It helps lower the budget of gauging tools and reduces the barriers in case of intrusive flow meters. 

Learn more: A complete guide on flow sensor and it’s working

Flow sensors are in three major classifications- mechanical, optical, and open channel. Each class has sub-classes that work in different ways but under the same principle. Let us look into their Details. 

What Are The Different Types of Flow Sensors?

1. Mechanical Flow Sensors

These are flow sensors that depend on moving parts to sense the flow movement. There are many types of mechanical flow meters. Some are made for clean fluids, while others are for dirty or corrosive fluids. The thickness of the fluid also determines the flow meter you can use.

Let us look at the different Mechanical flow sensors in the market. 

Positive Displacement Flow Sensor:

These are flow sensors that first trap the fluid within them then release it. Thus, all the volume passing is known. The flow rate determines the number of times the water volume downstream. Due to that, the sensors have high accuracy. There are several types of Positive Displacement Flow Sensors. The difference is in the shape of the part that entraps the fluid.

PD meters are suitable to use with all kinds of fluids. The viscosity of purity of a fluid does not affect the function of a Positive Displacement Flow Sensor. However, due to their moving parts, they need regular maintenance and calibration. The different types include gear sensors, oval gear sensors, oscillatory/rotary piston sensors, nutating disk sensors, and helical gear sensors. 

Mass flow Sensor

This is another category of a flow sensor that gauges the flow through the mass of the fluid. They are of different types and are useful in fluids under extreme heat and pressure conditions. 

Thermal flow meters and Coriolis flow sensors are the major types under this category. They are more useful in chemical, gas, mining, wastewater, pharma, and power industries.

In the Coriolis flow sensors, the sensor works under the principle of motion mechanics. The fluids get into the sensor and split. Then the fluid oscillates in the opposite direction as the tube. In the process, a voltage in the form of a sine wave.

The thermal flow sensor has two working principles. In the two types, they have two heat sensors. They only differ in how they work. One type uses both sensors to heat the liquid. They gauge the energy required to maintain the heat as produced on the first sensor. In the second type, the second node measures the fluid temperature difference between the first heating node. 

Float Flow Sensors

These types of sensors are mainly used in water pumps. The sensor can detect high and low levels of water/fluid in the storage unit. It also can initiate action such as switch on and off. It floats on top of the liquid.

Know more: What is a Water Flow Detector, and How it Works?

There are several types of float meters. They are designed according to the type of fluid, viscosity, and other fluid parameters.

Turbine Flow Sensors

These meters are mainly found in large-capacity industries. They are among the cheapest meters and have high accuracy. They have a rotating turbine that turns as the fluid passes through the vanes. However, the meter requires fluids with low viscosity and little to no sediments.

Turbine sensors need high maintenance when the fluid carries a lot of sediment. However, the industries that use turbine sensors do not require high accuracy. 

Vane Flow Sensor

They are also known as variable area flow sensors. It is an intrusive type of flow meters whose immersed part shifts with the flow- The sensor detects these movements. It is called a vane sensor since it has a vane and a spring opposite. Moving fluid pushes the vane against the spring. The flow rate determines the movements. If you want to capture the data, then you should attach the sensor to a transmitter. 

2. Optical flow Sensor

Optical sensors work under the principle of light. It does not have to be visible light. In most cases, the sensors are made with a photosensor and a laser beam.

Optical sensors work well with dirty fluids. The particles of bubbles in the fluid scatters the laser beam. Then the sensor will detect the movement of the scattered laser beam. In the process, they produce a pulse. Then a receiver picks up the pulse; The sensor will assess the distance the pulse is covered and the time used. It helps assess the speed of the fluid. 
These meters work on all types of fluids. It does not get affected by fluid parameters like viscosity, pressure, temperature, etc. 

3. Open Channel Flow Sensors

These are flow sensors that you use in fluids flowing on free surfaces. Thus, the meters or sensors are greatly used for irrigation purposes. Flumes and weirs are the common meters of these types. However, you will need a floating meter combined with any of the two if you need to get a signal remotely. 

Conclusion

The principles of flow sensors are easy. You only need to know your fluid parameters before you select one type of sensor. Also, you should know what your firm needs and the effect that can arise should the tool fail to work properly.