What is Flow Switch and How to Select Flow Switch

A flow switch is a device that monitors the flow of liquid, gas, or steam. When the flow reaches a certain pre-set flow rate(for example 0.12L/min), a flow switch is triggered to signal an action, such as shutting down the flow. When the flow is less than the set value, a flow switch returns to its original position.

Flow switches are widely used in systems requiring flow control, such as pump control, fire fighting systems, etc., which can accurately start or stop equipment according to flow changes, improving the efficiency and reliability of the system. Flow switches can be divided into many types according to different working principles and application scenarios, mainly including mechanical, electromagnetic, ultrasonic and thermal.

1, Mechanical flow switch. This type of switch uses the pressure difference or power generated by the fluid flowing through the device to drive the mechanical structure. Common switches are turbine, vortex and piston. The turbine type flow switch detects the velocity through the rotation of the rotor blade, the vortex type through the vortex effect, and the piston type uses the fluid pressure difference to complete the switching operation.

2, Eelectromagnetic flow switch：through the electromagnetic principle in the sensor to detect the flow rate of fluid, with high sensitivity and accuracy, suitable for measuring the flow of various liquid media. BST's unique design of flow switch is base on reed technology. In the sensor, a reed switch and a magnet are included, when the pre-set flow rate is reached, the magnet is able to trigger the reed switch. Hence the electrical system is able to turn on or shut down.

3, Ultrasonic flow switch: the use of ultrasonic characteristics to measure the flow rate, suitable for a variety of media, not affected by the medium composition and temperature, with high measurement accuracy and reliability.

4, Thermal flow switch：by measuring the heat exchange of fluid medium to detect the flow rate, including thermistor type, thermocouple type and thermistor type.

Selection Guidance:

When choosing a flow switch, the following factors need to be considered:

1, Fluid medium ‌ : Understand what kind of fluid medium to be measured, such as liquid, gas or steam, because different fluid media may have different requirements on the material and working principle of the flow switch.

2, Flow range ‌ : Determine the flow range you want to measure, including minimum and maximum flow values, and select a flow switch with the appropriate measuring range.

3, Accuracy: Select the flow switch with the appropriate accuracy level according to the accuracy requirements of the application scenario. Considering the environmental conditions under which the flow switch will be installed, including temperature, pressure, humidity and corrosion, choose the flow switch suitable for the working environment to ensure its stable and reliable operation.

4, Material selection: According to the chemical properties of the fluid medium and temperature range, choose the appropriate material,  for example: stainless steel, copper, PVC, PP and so on.

By taking these factors into consideration, the flow switch that is most suitable for the application scenario can be selected to ensure that it can work accurately and reliably.

BST sensor, a manufacturer for flow switch, reed sensor, hall sensor and magnetic components.