by
Mohamed Elnakib , Instrumentation and control systems engineer -Al shabab power project Phase II , Pgesco
dry contacts are powerless (voltage free) contacts , wet contacts (non-dry contacts) on the other hand should include voltage .
dry contacts are mainly used to close the loop in order for an action to occur , for example a limit switch dry contacts close , closing the loop which gives the indication to the DCS that the limit switch has closed .
by
Mohamad Yahya Mahmoud Zaid , Instrumentation and Control Consulting Engineer مهندس استشاري أجهزة دقيقة و تحكم آلي , Petroleum Pipelines Company (PPC) شركة أنابيب البترول
there are two answers for that question 1- it's according the contacted device , if it is passive (no power supply) so it need a wet contact,
if it have it's own power supply so it just need a dry contact,
in other words ,,, dry contact is a relay output without providing any volt.
and wet contact is including a volt.2-dry contact is the carbon contacts, wet contacts is a mercury contacts.
