Terminology for digital IO - "dry contact", "wet contact"

[nongspits]

I am a software developer, and have implemented support for various digital I/O devices (via TCP/IP, such as ModBus). I am about to write some documentation for internal use, and the terminology being used around is kinda confusing.

These devices used ports that are either active low or active high (or, configurable to either). In some cases, "dry contact" and "wet contact" are being used. So, are these statements correct ?

• Dry contact = active low = pull to ground to set HIGH

• Wet contact = active high = needs a voltage to set HIGH.

[K C]

Hi,

Using and understanding names and terminology is not always the same at every place, country, company, etc.

This is what I know:

Active low = A logic '0'    Pull to ground to set true (Not high !!). I think in most cases this is true but not always. 

Active high -  A logic '1'   Set to high voltage to set true (Not high !!). I think in most cases this is true but not always.

Dry contact is a voltage free contact. The contact is isolated from the control part. i.e. a relay contact

Wet contact is contact that is not isolated from the control part.

Kees