Types of Relays 继电器的类型(下)更新于2008-05-19 11:22:22
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继电器 开关手册
2.2.5 水银湿簧继电器
note: Mercury is listed as a banned substance under the Restrictions of Hazardous Substances (RoHS) Directive, therefore limiting the application of these relays.
Mercury wetted reed switches are constructed in the same way as dry reed switches with the addition of a small amount of mercury inside the glass tube. This is shown in Figure 2-6. The mercury wicks up the reed and wets the contacts,providing a perpetually self-renewing contact surface. Mercury wetted relays have a higher current handling capability and longer lifetimes than dry reed relays.
A position insensitive mercury wetted reed relay is also available. As Figure 2-6 shows, the standard mercury wetted reed relay must be used within 30 degrees of its upright position or the pool of mercury shorts the contact. Position insensitive switches avoid this problem by using only enough mercury to wet the reed and contact area, as seen in Figure 2-7. Life specifications for this type of switch are longer than dry reed switches but shorter than normal mercury wetted
switches.
The self-renewing contact surface of mercury wetted switches, combined with the other advantages of a reed relay, makes mercury wetted reed relays attractive for some switching systems. Relatively high cost and limited operating orientations
are drawbacks with this type of relay.