1 Flow Sensor Manufacturers in 2023

What Is a Flow Sensor?

A flow sensor is a detector that measures the flow rate of any fluid, from gas to liquid.

There are various types of flow sensors, including analog flow sensors that monitor the fluid flowing in a fluid circuit for abnormalities and digital flow sensors that are connected to a feedback control mechanism to adjust the gas supply to a certain volume.

Uses of Flow Sensors

Flow sensors are incorporated in fluid circuits and are also used in familiar applications such as flow sensors for monitoring and investigating water flow through pipes and flow sensors for measuring and adjusting the flow of gases.

Flow sensors are not limited to water and air, but are also available for special gases such as etching gas used in semiconductor manufacturing sites.

On the other hand, if the appropriate flow sensors are not selected, not only will the correct flow rate not be measured, but underestimation of flow rate can lead to rupture of the flow path, etc. Therefore, one is almost certainly used in situations where fluid control is required.

Principle of Flow Sensors

Although various measurement formats are employed depending on the internal structure and the fluid to be measured, this section describes the principle of differential pressure flow sensors, which are applicable to common fluids such as air and water.

Differential pressure flowmeters use Bernoulli's theorem to measure flow rate.

It introduces a mechanism that intentionally narrows the flow path in a fluid of a certain size. By doing so, a pressure drop is created in the fluid, and the pressure before and after the drop changes.

By measuring each of these pressures, the flow velocity can be calculated based on Bernoulli's law.

There are various types of flowmeters, such as orifice type and nozzle type, depending on the mechanism used to narrow the flow path, but all of them are the same in that they measure the pressure difference between the fluid before and after the orifice.

How to Select Flow Sensors

The appropriate flow sensors depend on the type of fluid to be measured.

If you select the wrong flow sensors for a gas or a liquid, you will not only recognize an incorrect flow rate but also risk a serious accident if you select the wrong flow sensors to measure the flow rate of a hazardous or flammable substance.

Therefore, it is important to start by carefully examining the properties of the substance to be measured.

In addition, flow sensors generally cannot measure a wide range at once. If the expected flow rate is determined in advance, it is recommended to select flow sensors with high accuracy for that range.

About Clamp-On Type Flow Sensors

"Clamp-on" means that the instrument is installed outside the piping through which the fluid to be measured flows. In this case, the instrument to be installed is the flow sensors. It cannot be installed depending on the material of the piping or the type of fluid flowing in the piping.

Clamp-on flow sensors are generally called ultrasonic flow meters or ultrasonic flow sensors and can be used as a measuring instrument if the object to be measured a fluid that can be measured by ultrasonic waves. The main fluids that can be handled include pure and chemical solutions, oil, cold and hot water, corrosive liquids, and highly viscous liquids. Ultrasonic flowmeters are available in various types, including time-of-propagation and frequency measurement using the Doppler method.

The advantages of ultrasonic flowmeters are that they can be installed without removing or cutting piping, which reduces installation costs, greatly improves maintainability after installation, and eliminates pressure loss in the piping. However, demerits include the fact that the meter is installed outside of the piping, so the length of the straight pipe section is necessary, and the diameter of the piping is also a factor, as well as the fact that measurement cannot be performed if the fluid to be measured contains many solids or bubbles.

About Air Flowmeters

Air flowmeters are available as clamp-on flowmeters or screw-connection flowmeters. The screw connection type eliminates the need for an intuitive part, making the measurement device compact and space-saving. In addition to piping, fittings can be attached to allow measurement with air or water tubing.

For example, conventional air flowmeters use a thermal mass flowmeter if the gas is to be measured a compressible fluid. And there are several measurement methods for thermal mass flowmeters. The most common of these is the capillary type, in which a flow element with a resistance value is installed inside the tube, and a heater is wound around the outside of the tube, with temperature sensors on both sides of the heater measuring the flow balance. However, thermal mass flowmeters are susceptible to contamination and are not good in low-pressure environments. Therefore, it is recommended that they should not be used in facilities with a lot of oil mist.

Currently, thermal mass flowmeters use a method called the flow sensors method. This type is composed of semiconductor flow sensors and has a wide measurement range, and can be used in low-pressure environments without worrying about contamination.

Although various methods have been devised to measure target fluids, there are restrictions on the flow sensors that can be used depending on the fluid to be measured, so it is desirable to carefully consider the operating environment and other factors before installing flow sensors in a facility.