信号清单中，信号类型Polarized Contact，Potential Fre ...？ fyi re: potential free contacts? 07/26/2010 1:47 pm the electrical contacts on a relay are potential free until you connect a wire with a voltage on it to the contact. another example is typically a flow or pressure switch. the contacts are like the contacts of a relay, there is no voltage connected to either from inside the switch. this style is also referred to as 'dry' contacts. wetted contacts have voltage applied to at least one of the contacts. (and yes, there are also mercury wetted contacts where the mercury carries current) the use of potential free contacts allows - connection to a device that sources its own voltage. - connection of multiple devices in series and/or parallel for relay logic control open collector, pnp or npn devices are not potential free or dry contact devices. 查看更多
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