A Reed Switch consists of a pair of ferromagnetic reeds, overlapping at their free ends (contact area) at a very small distance and hermetically sealed in a glass tube. The contact area is plated with contact material such as Ruthenium or Rhodium. In presence of a magnetic field the reeds become magnetized the opposite polarity, thus attracting each other and closing contact.
ACTUATING A REED SWITCH
In general four different magnet approaches are known when using permanent magnets.
ONE POLE ACTUATION
One magnet pole faces Reed Switch providing two operations max. when moving on X-axis. Minimum movement of magnet over switch center provides smallest possible switching differential.
Approaching magnet vertically to switch on Y-axis provides one operation only. Driving magnet over the full length of the switch (X-axis) may result in up to three operations. Minimum movement of the magnet over switch centre provides the smallest possible switching differential.h.Properties and behaviour of Reed Switches and Reed Sensors.
Rotation of the actuating Magnet: Two switching cycles per full turn of the Magnet.
Operation of switch by shielding. This method requires a permanently opposite location of magnet and switch. The switch is held closed continuously and will release only if magnet flux is removed by means of ferro-magnetic shield.