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Schematic Design of Paddle Flow Switches, Why it Shows wrong indication ?

Flow switch is a special electric device with a very simple design and of a small size, as a mechanical switch that is switched on or off in response to the flow or non-flow of a fluid such as air or water. The switch typically operates through the use of a paddle which gets displaced due to the force of fluid moving past it. But despite of its simplicity, flow switch plays important role in the variety of different applications.

Schematic Design of Paddle Flow Switches

The flow switch consists of a paddle system (1) which has a permanent magnet (2) located at its upper end. A reed contact (3) is positioned outside the flow above this magnet. A second, magnet (4) with opposite polarity is used to create a reset force.

The paddle system is moved once it comes into contact with the flow which is to be monitored. The magnet (2) changes its position in relation to the reed switch contact (3). The contact opens/closes depending on the contact type.

As soon as the flow is interrupted, the paddle returns to its original position and the reed switch contact opens/closes depending on the contact type. This change in contact (NO to NC or NC to NO) will be used to indicate the required flow signal output.

GE-313 Teflon PTFE Plastic Paddle Flow Switches

This flow switch is produced by teflon plastic material with a long paddle, combats the problems of ...

These switches find application in the detection of fluid flow and measurement of fan speeds.

A flow switch might be used to protect a central heating system electric heating element from being energized before the air flow from the blower is established.