Dry Contact?


Old 05-13-09, 03:47 PM
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Dry Contact?

I believe the term "Dry Contact" is used more commonly in the alarm industry. Can anyone here explain or point me to a site that contains a good basic explanation of what a "Dry Contact" is and how it is used?

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Old 05-13-09, 05:59 PM
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dry contact

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.
Old 05-13-09, 06:06 PM
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"Dry contacts" are relay switch contacts that are electrically isolated from the power that energizes the relay coil. Three classes: Form A (Normally Open); Form B (Normally Closed) and Form C (single pole-double throw).

It's mostly a north-american terminology; I think they call it something like "volt-free" or "zero-volt" contacts in Europe.

Here's a pretty good "white paper" on relays:

Old 05-15-09, 12:57 PM
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Thank you both for your prompt replies. After reading the information in the link I now have a better understanding of dry contacts.

Thank you again.
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