Sealed contact relays

The construction and properties of dry reed and mercury contact relays are discussed. The dry reed relay provides gold plated contacts with a single make action. It operates in a magnetic field of about 100 ampere turns and releases at about 40 ampere turns. It can be made to operate in about 1 ms with little contact bounce. The contacts have low contact resistance and can handle up to 15 VA at a maximum current of ¿A. The mercury contact relay is a polarized relay with a single changeover action in which the contacts are wetted with mercury. Typical operate-release values obtained by adjustment of polarizing permanent magnets are 60 and 40 ampere turns respectively. It operates in less than 1 ms with complete freedom from contact bounce. The maximum load is 25 VA with a maximum current of 5 A. The relays find their main applications where contact reliability is essential and some app1ication of special interest are briefly described.