A basic flow switch is a device designed to detect the flow of a fluid (such as gas or liquid) in a pipe or conduit and trigger a response based on that flow. The mechanism used to detect gas flow can vary depending on the specific type of flow switch, but here's a general explanation of how a basic flow switch typically works to detect gas flow in pipes:
Mechanical Flow Switch:
One common type of flow switch is the mechanical flow switch. It consists of a paddle or vane that is positioned in the path of the gas flow within the pipe. When gas flows through the pipe, it exerts force on the paddle or vane, causing it to move or rotate.
Reed Switch Flow Sensor:
Another type of flow switch uses a reed switch as the sensing element. A reed switch is a small, magnetically operated switch that consists of two ferromagnetic reeds inside a hermetically sealed glass tube. When gas flows through the pipe, it may pass through a small chamber that contains the reed switch. The gas flow generates a magnetic field (by means of a magnet or a magnetic element attached to the moving fluid), which causes the reeds to either attract or repel each other, resulting in the opening or closing of the switch.
Thermal Flow Switch:
Thermal flow switches operate based on the principle of heat transfer. These switches consist of a thermal sensor or thermistor placed in the gas flow path. When gas flows through the pipe, it carries heat away from the sensor. The rate of heat transfer is proportional to the flow rate. The thermal sensor measures changes in temperature caused by the gas flow and triggers the flow switch accordingly.
Ultrasonic Flow Switch:
Ultrasonic flow switches utilize ultrasonic waves to detect flow. They consist of a transmitter and receiver positioned opposite each other across the gas flow path. The transmitter emits ultrasonic waves, and the receiver detects them. When gas flows through the pipe, it affects the travel time of the ultrasonic waves between the transmitter and receiver. The flow switch monitors the time delay or phase shift in the ultrasonic waves and triggers the switch based on the changes caused by the flow.
Once the flow switch detects a certain flow rate or presence of flow, it triggers an electrical signal to initiate a specific action, such as turning on or off a pump, activating an alarm, or sending a signal to a control system.
It's important to note that the specific type of flow switch and its detection mechanism will depend on the application, the type of gas being measured, the flow rate range, and the required accuracy of the measurement. Different industries may use different flow switch technologies based on their specific needs.