A reed relay is a type of relay that uses reed switches as its switching elements. Reed switches are small, hermetically sealed glass tubes containing two ferromagnetic reeds with contacts at their ends. When a magnetic field is applied externally, the reeds attract each other, closing the contacts and completing the electrical circuit. Here’s how a reed relay switch typically operates:
- Reed Switch: The heart of a reed relay is the reed switch, which consists of two thin metal reeds inside a sealed glass envelope. The reeds are made of ferromagnetic materials such as nickel-iron alloys. In their resting state, the reeds are separated and the contacts are open.
- Coil: The reed relay also includes a coil wound around the glass envelope of the reed switch. When a current passes through the coil, it generates a magnetic field.
- Magnetic Field Activation: When the coil is energized, the magnetic field generated by the coil attracts the reeds towards each other, causing them to make contact. The strength of the magnetic field required to close the contacts depends on the specific reed switch’s characteristics.
- Contact Closure: As the reeds come into contact, the contacts of the reed switch close, allowing the current to flow through the relay. This completes the electrical circuit and enables the relay to control the load connected to its contacts.
- Contact Opening: When the coil is de-energized, the magnetic field dissipates, and the spring tension of the reeds causes them to separate, opening the contacts and interrupting the circuit.
Reed relays are known for their fast switching times, low contact resistance, and excellent electrical isolation between the coil and the contacts. They offer advantages such as low power consumption, compact size, and high reliability due to the hermetically sealed construction. Reed relays find applications in areas where low-level signals or fast switching are required, such as telecommunications, automated test equipment, medical devices, and instrumentation.