The reed like contacts of a reed relay are encapsulated in a small sealed glass tube that is evacuated or filled with an inert gas like dry nitrogen as illustrated in the figure below:

Reed relay
Figure 1(a) reed relay

The contacts are activated by an external magnetic field. The contacts are either dry or mercury-wetted. Mercury-wetted contacts have a thin coating of mercury that fills in surface irregularities, making a larger conduction area and reducing pitting.

In general, reed relays have a long life and low-coil voltage (often, TTL compatible),have faster switching speed compared to electromechanical relays and are immune to dirty environments, nevertheless, they are generally low power (contacts rated at 2 A or less) and vibration sensitive.

Related: Solid-state Relays (SSR) Features and Operation

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John Mulindi

John Mulindi is an Industrial Instrumentation and Control Professional with a wide range of experience in electrical and electronics, process measurement, control systems and automation. In free time he spends time reading, taking adventure walks and watching football.

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