DRY CONTACT

Not wet...

Not mercury wetted, or immersed in oil ?

Del

guest; i feel that it is a low current rated contact used in electronics ,Rather then the higher power used in electrical 1 amp & up perry

In instrumentation the term is sometimes used to refer to a set of contacts performing some switching function, and that change state according to some feature of the instrument. The important point to note is that they are isolated from internal circuitry, and their use relies on power brought to the instrument independently of its own power supply. An equivalent term is "volt-free contact".

For example, consider a loop-powered analog level instrument with a high alarm contact. The loop will usually be from a 24VDC power supply that may power a number of different loops. The dry contact might be wired in series with the contactor that switches off the fill pump when the level goes high, and that circuit might run at 110VAC, and so-on.

volt-free contact

Agree. Though I've never seen a definition (have to do that after this), from the use of the term in manuals, these are voltage-free contacts from internal relays that you can use any way you wish (as long as you stay within the contact's rating, that is).

For illustrative purposes, the one on the left is a dry contact and the one on the left is...er...wet?

Might the term come from the tendency to wet your pants in case you happen to touch the contact that had 120-220VAC on them?

I would dare to suggest that it'd been called so in contrary to opened p-n transition for semi-conduct relay like in an open-collector scheme. As there is always some "leakage" of current. Word "leakage" is a clue maybe. It's only my supposition.

Well the last three answers have just about described what I've understood and been told for the term 'dry contacts'...!!

There seems to be about 3 different meanings for the term, the most common one I know is to distinguish between mercury wetted contacts and normal contacts... Also I've heard the term used for low power or signal switching contacts...

I must admit I've not heard about dry contacts being referred to as volt free contacts though...

But it does seem to be a very loose description!!

John.

I have also seen/used the term to describe testing contacts with no voltage applied to them in order to see if they are working. I have also seen/used it to apply to manually cycling contacts with no control/power voltage on them in order to troubleshoot the contactor/starter.

Ditto. When I ask factory people to supply "dry contact" to be connected to PLC we're implying similar thing. But it is some informal term though.

Dry contact means potential free contact (also can be say anti bouncing contact) only switching capabilities digital circuitary (not energising big relays or slenoid) I have given you a little examples only .