Operating Characteristics of a Reed Switch
The following examples show typical operating characteristics of a reed switch when actuated with a magnet from various axes. Generally, when a reed switch is actuated by a permanent magnet, the ON-OFF region differs depending on the type and Operate AT of the switch, and size and strength of the permanent magnet. The ON region corresponds to the Operate AT and the ON region and the Hold region together corresponds to the Release AT of the Reed Switch. These characteristics will vary if there is any other Ferro-magnetic material nearby. Each characteristic curve will be enlarged as a whole if a stronger magnet is used for actuation, or if the Operate AT of the reed switch is low.
Magnet Perpendicular to Width of Reed Blades
In this sketch, the magnet is shown perpendicular to the reed switch, with one pole towards the reed switch and the other away from the reed switch. As shown, when the magnet is moved up and down, right towards the middle of the reed switch, near where the blades are overlapped, no actuation will take place. If the magnet is move up and down towards one of the reed blades, the reed switch operates. If the same perpendicular magnet is moved across the length of the reed switch, the reed switch opens when the magnet is at the center of the overlapping blades.
Magnet Parallel to Width of Reed Blades
In this sketch, the magnet is shown parallel to the overall length of the reed switch. In this position, when the magnet and reed switch are parallel and centered longitudinally, and the magnet is brought closer to the reed switch, the two poles of the magnet induce their opposite polarities on the respective reed blades and the reed switch closes. If the magnet is moved away from the center, towards the left or right, and then moved to approach the reed switch, one of the poles of the magnet will be outside the length of the reed switch. This is equivalent to single pole actuation.
Magnet Perpendicular to Thickness of Reed Blades
In this sketch, the magnet is shown in an axis perpendicular to the reed switch. This type of approach could also be stated that the magnet is perpendicular to the thickness of the reed blades, from another perspective. In this position, when one of the poles of the magnet is approaching the reed switch at the center of its overlap, the reed switch get actuated. But if the same magnet along the same axis, is brought towards only one blade, the magnetic field is perpendicular to the reed blade and does not have the necessary flux to induce the reed blade to actuate the reed switch.
Magnet Rotating 360º to Reed Switch
In this sketch, the magnet is shown rotating along its longitudinal axis, near the reed switch, and explains the actuation ranges for pulse counting applications. The position of the magnet is always at a fixed distance from the reed switch, at a point where when the magnet is parallel, it does not actuate the reed switch as shown in the second sketch above. After fixing this point, the magnet is rotated along its axis and the single poles of the magnet alternately induce the reed blades and turn the reed switch on and off. It should be noted that if the fixed distance of the magnet is too close to the reed switch, alternating on and off states will not be achieved.