How does a thermal reed switch sensor work ?
A special ferrite compound which loses its magnetic permeability at its Curie temperature, is sandwiched between two permanent magnets. At temperatures lower than the Curie point, the magnetic flux lines between the two exterior magnets are connected and enlarged as a whole. This keeps the reed switch contact closed. When the ambient temperature reaches the ferrite’s Curie temperature, the flux no longer passes between the exterior magnets, and the reed switch contact opens. Normally open type of thermal reed sensors are made by positioning the magnet assembly, slightly away from the reed switch contact overlap. Click here to download this page as a PDF.
