The paddle switch is designed to detect high or low levels of free-flowing dry solids, such as powders
and granules. It is mounted through the wall of a vessel such that the paddle protrudes inside the vessel.
A small electric motor drives a paddle that rotates feely in the absence of material, but is impeded when material
is present. When the paddle is impeded, a micro-switch output activates to signal an alarm.
To extend the motor life, power is cut to the motor whenever the paddle is free of material. Upon contact with
material, the power is restored to the motor once again, therefore rotating the paddle.