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What is Dry Contact

  1. Nov 16, 2013 #1
    I am confused about dry contact. Does it mean dry contact vs wet contact as in mercury switch vs regular relay.
    Any circuit examples.
    Are transistor switches also referred to as dry contacts.
    Is a NPN transistor with open collector output also referred to as dry contact?
  2. jcsd
  3. Nov 16, 2013 #2
    Almost always means that the relay itself does not provide a source of voltage or current.
    The contacts are simply two conductors coming into contact.

    The equipment that is monitoring the dry contact must provide voltage/current to sense the state of the relay.
  4. Nov 17, 2013 #3
    I always used "dry contacts" basically as an interrupting circuit or relay output;

    For example with a resistance furnace power always goes through a dry contact before the solid state relay. the dry contact functions as the over temp/alarm/permissive signal and the solid state as the control.

    Many industrial instruments have "dry contact" relays in them which can be used to start/stop a completely separate circuit.
  5. Nov 18, 2013 #4


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    Wet contact, to me, means mercury wetted contacts which are literally wet with mercury.

    Dry contact either means no mercury or a little current that controls a larger contactor, depending on the context of its use.
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