what is exactly meant by "dry contact"

[Gibson486]

They throw this term around at work. I asked someone and they just gave me a weird look like i was stupid I searched google and all i can find is that it is a contact where no voltage or current is made or passed. That makes no sense to me because why else would you have a contact? Would a relay be considered a dry contact? Or does the dry contact just refer to the contact part and not the coil?

 

[PottedMeat]

Apparently dry = you get 2 contacts not connected to anything -> you decide how to sense it ( apply a voltage where +V = closed, 0V = open or however you want to do it )

http://www.control.com/1026171624/index_html

I googled 'wet contact relay'.

 

[bobdole369]

PottedMeat is right.

Dry contact means - 2 bare contacts. You supply power, no ground or power is supplied.

We use them all the time.

We supply our OWN power or ground. Our system is electrically isolated.

The point - when you need a power or ground-free switch. Such as when you don't want a vendors 99kW generator set to share ground with your terribly delicate monitoring system and turn your circuits into crispy shadows of their former selves.

Or, if you want to press another vendors switch, while not interfering with their circuitry which would happen if you used an ordinary sinking or sourcing switch.

 

[skyking]

Just to add, a set of dry contacts will have a voltage and current limit associated with it. If you need to run a larger load, use an external relay per the manufacturer's instructions.

 

[dkozloski]

We oldtimers used to refer to reed relays meant for low level signals with gold or silver plated contacts as "dry contact" as opposed to relays with mercury "wetted contacts" which were used to reduce noise from bouncing contacts. For instance, we used a mercury wetted relay to switch a reference voltage in response to a signal from a time standard for down range timing on a missile range. This produced a nice clean 1pulse/sec square wave. The typical dry contact relay would produce switching noise at both opening and closing. The square wave most commonly drove the timing pen on an Esterline-Angus or Sanborn chart recorder.

 

[eits]

dry contact = non-sexual contact

 

[dkozloski]

Like a dry rub?

 

[krle]

On frequency converter, I have dry contact. When I close that contact, over my logic, frequency converter starts to work.
So, how frequency converter knows that contact is closed ? That all loop is dry (without any power supply). Does frequency converter send some signal over that dry contact to check its state ?

Please don't bump 5 year old threads
-ViRGE