Types of Relays 继电器的类型（下）
Types of Relays 继电器的类型（下）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.
注：根据《限制电器及电子设备使用有害物质(RoHS)》规范，水银被列为被禁用物质，从而限制使用这类继电器。
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.
水银湿簧开关与干簧继电器的构造方式相同，仅仅是在玻璃管内部增加了少量了的水银。如图 2-6所示。水银沿簧片渗透并沾湿触点，形成一层永久性自更新接触表面。与干簧继电器相比，水银湿簧继电器具有更高的电流处理能力和更长的寿命。 图2‑6Figure 2-6. Mercury wetted reed switch图 2-6 水银湿簧开关
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.
还有一种对方向不敏感的水银湿簧继电器。如图 2-6所示，标准的水银湿簧继电器在使用时必须保持在垂直方向的±30°范围之内，否则水银将会短路触点。而对方向不敏感的开关仅使用足以沾湿簧片和触点区域的水银量量，如图 2-7所示。这种类型开关的寿命比干簧开关要长，但是比常规的水银湿簧开关要短。 图 2-7 水银湿簧开关
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.
水银湿簧开关的自更新接触表面，再加上簧片继电器的其它优点，使得水银湿簧继电器对有些切换系统非常具有吸引力。但相对较高的成本和受限的工作方向是这类继电器广泛使用的障碍。
2.2.6 固态继电器
Solid state relays are typically comprised of an opto-isolator input, which activates a solid state switching device such as a triac, SCR, or FET. Although these are the fastest switching elements when actuation times are compared, the release, or turnoff time, is long. AC control is a normal application for triacs and SCRs because the turnoff time is decreased when the device is switched off during a zero-crossing. Also, their isolation is limited by the leakage currents of the semiconductor devices, and they have a high insertion loss for low level signals.
固态继电器通常包括一个光隔离输入，该输入激励一个固态开关器件，例如双向晶闸管、SCR（可控硅）或FET（场效应管）。尽管在比较激励时间时这类继电器是最快的切换元件，但释放或关断时间却比较长。由于器件在过零时被关断会降低关断时间，所以双向晶闸管和SCR通常用于交流控制。此外，其隔离受半导体器件漏流的限制，并且对低电平信号具有较高的插入损耗。
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