This section provides overview, applications, and principles of reed switches. Also, please take a look at the list of 26 reed switch manufacturers and their company rankings.
A reed switch is a switch with two magnetizable reeds in a glass tube that turns electrical contacts on and off.
When open, a typical reed switch opens with a small gap between the reed contact edges. When an external magnetic field (e.g., a magnet) is applied to the two reed contact edges, the reed contact edges attract each other and close, closing the circuit.
Reed switches are used in the following applications
Magnets turn Reed switches on and off, so they can be used for non-contact detection. Reed switches are mainly used for the non-contact detection of equipment status.
The components of a reed switch include a glass tube, a reed strip, a magnet, and a contact.
Since the contacts are not contaminated, the reed switch has very low contact resistance. The contacts are mainly made of metal and have a short operating distance, giving them an open/close life of up to several hundred million cycles.
Reed switches are components with moving parts. Therefore, there is no possibility of failure. The main possible failures include contact failure, contact sticking, and unexpected malfunction.
Factors that can cause contact failure include deterioration of the magnet over time and carbonization due to chemical changes on the contact surfaces. Since carbonization of the contact surface is unlikely to occur in a nitrogen atmosphere, the glass capillary may be cracked.
Contacts may stick due to deterioration of the spring or welding of the contacts due to overcurrent. Deterioration of the spring is mainly due to aging, while welding of the contacts may be caused by an abnormality on the electric circuit side, so caution is required.
Unexpected malfunctions may be caused by a random combination of the above two causes. In this case, it is very difficult to identify the cause.
Reed switches are components that have a relatively low probability of failure. To deal with failures, it is essential to design circuits with redundancy and prevent malfunctions. In addition, since reed switches are inexpensive, they are sometimes designed from the outset on the assumption that they will be replaced at regular intervals.
Reed switches are used to sense the proximity of a magnet. However, the operating range over which the switch operates is not uniform, so there is a risk of chattering. Equipment design must take chattering into consideration.
On the other hand, the distance between the contacts of a reed switch is very small, and the contact pressure is very slight. Because they are precision components, they must be used strictly within their rated current values. In addition, even when used within the rated current value, care should be taken not to apply strong shocks.
In addition, the use of reed switches under strong magnetic fields may cause malfunctions. A magnetic shield should be provided to block external magnetic forces in such an environment.
*Including some distributors, etc.
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