Dry contact是什麼意思

"Dry contact" is a term commonly used in the context of electrical circuits and devices, particularly in the realm of automation, control systems, and telemetry. A dry contact refers to a type of electrical connection where the contacts (the points where two conductors meet) are not connected to a power source or do not have a voltage applied to them under normal circumstances.

In other words, a dry contact is an open switch that does not have any current flowing through it when it is not being activated. When the switch is closed, current can flow, but when it is open, there is no electrical connection. This is in contrast to a "wet contact," which is a term used to describe a contact that is always connected to a power source and is therefore "live" or "hot."

Dry contacts are often used in sensors, switches, and other devices that need to communicate the status of an event or condition to a control system without actually providing power to the system itself. For example, a dry contact might be used in a motion sensor that is designed to turn on a light when it detects movement. The sensor would close the switch (making the contact "live") when it detects motion, which would then complete the circuit and turn on the light. When the motion stops, the switch would open (returning the contact to "dry" status), and the light would turn off.

Dry contacts are useful in a variety of applications where it is important to be able to detect the state of a device or system without introducing the risk of electrical shock or the need for a separate power supply for the sensor or switch. They are also commonly used in alarm systems, security systems, and other types of monitoring and control systems where it is important to be able to detect changes in the environment or the status of a device without introducing the risk of electrical shock or the need for a separate power supply for the sensor or switch.