Dry contact may mean any of the following in electronics: * ''No current'': A dry contact is the synonym of volt free — it is not "wetted" by a voltage source. Dry contact can refer to a secondary set of contacts of a

relay A relay Electromechanical relay schematic showing a control coil, four pairs of normally open and one pair of normally closed contacts An automotive-style miniature relay with the dust cover taken off A relay is an electrically operated switch ...

circuit which does not make or break the primary current being controlled by the relay. Usually some other contacts or devices have the job of starting or stopping the primary current being controlled. For example, a

reed relay A reed relay is a type of relay that uses an electromagnet to control one or more reed switches. The contacts are of magnetic material and the electromagnet acts directly on them without requiring an armature to move them. Sealed in a long, nar ...

matrix switch is normally switched with all contacts dry. After the contacts are all connected, a

wire spring relay A wire spring relay is a type of relay, that has springs made from drawn wires of nickel silver, rather than cut from flat sheet metal as in the flat-spring relay. This class of relays provided manufacturing and operating advantages over previous d ...

is energized and connects a supervisory scan point, or main switch, through which the primary current being controlled then flows. Dry contacts are primarily employed in

extra-low voltage Extra-low voltage (ELV) is an electricity supply voltage and is a part of the Low voltage bandIEC 61140:2016 Chapter 4.2 in a range which carries a low risk of dangerous electrical shock. There are various standards that define extra-low voltage. ...

(less than 50 V AC) distribution circuits. * ''No mercury'': The wet contact of a

mercury-wetted relay A relay Electromechanical relay schematic showing a control coil, four pairs of normally open and one pair of normally closed contacts An automotive-style miniature relay with the dust cover taken off A relay is an electrically operated switch ...

gives certain operational advantages. Dry contacts means a relay that does not use mercury-wetted contacts. * ''Dry joint'': A dry contact can be confused with a '' dry joint'', which is a type of poorly

soldered Solder (; NA: ) is a fusible metal alloy used to create a permanent bond between metal workpieces. Solder is melted in order to wet the parts of the joint, where it adheres to and connects the pieces after cooling. Metals or alloys suitable ...

joint in which the

solder Solder (; NA: ) is a fusible metal alloy used to create a permanent bond between metal workpieces. Solder is melted in order to wet the parts of the joint, where it adheres to and connects the pieces after cooling. Metals or alloys suitable ...

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 unsatisfactorily soldered joint.

See also