Dry contact
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Dry contact may mean either of the following in electronics:
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[edit] No current
Dry contact refers to a contact of a relay which does not make or break a current. Usually some other relay or device has the job of starting or stopping the current. For example, a reed relay matrix switch is normally switched with all contacts dry. After the contacts are all connected, a wire spring relay connects a supervisory scan point, through which the current flows.
[edit] No mercury
Wet contacts are mercury wetted, which gives certain operational advantages. Dry contacts means a relay that does not use mercury wetted contacts.
[edit] Dry joint
A dry contact can be confused with a dry joint, which is a type of badly soldered joint in which the solder failed to wet the metal. These are liable to fail electrically. The term dry joint is also used less precisely to mean any sort of unsatisfctorily soldered joint.
