Dry Contact: Definition, Examples, & More

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SUMMARY

Dry contact refers to a relay or switch that does not provide its own voltage or current, requiring external equipment to sense its state. It is commonly used in industrial applications, such as in resistance furnaces, where it acts as an interrupting circuit before a solid-state relay. The discussion clarifies that dry contacts can include various types of relays, including those with NPN transistor open collector outputs, and distinguishes them from wet contacts, which involve mercury-wetted mechanisms.

PREREQUISITES
  • Understanding of relay types, specifically dry and wet contacts
  • Familiarity with NPN transistor operation and open collector outputs
  • Knowledge of solid-state relays and their applications
  • Basic principles of circuit design and monitoring systems
NEXT STEPS
  • Research the differences between dry contacts and wet contacts in relay technology
  • Learn about the applications of NPN transistors in circuit design
  • Explore the role of solid-state relays in industrial automation
  • Investigate how to implement monitoring systems for dry contact relays
USEFUL FOR

Electrical engineers, automation specialists, and technicians involved in industrial control systems and relay applications will benefit from this discussion.

likephysics
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I am confused about dry contact. Does it mean dry contact vs wet contact as in mercury switch vs regular relay.
Any circuit examples.
Are transistor switches also referred to as dry contacts.
Is a NPN transistor with open collector output also referred to as dry contact?
 
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Almost always means that the relay itself does not provide a source of voltage or current.
The contacts are simply two conductors coming into contact.

The equipment that is monitoring the dry contact must provide voltage/current to sense the state of the relay.
 
I always used "dry contacts" basically as an interrupting circuit or relay output;

For example with a resistance furnace power always goes through a dry contact before the solid state relay. the dry contact functions as the over temp/alarm/permissive signal and the solid state as the control.

Many industrial instruments have "dry contact" relays in them which can be used to start/stop a completely separate circuit.
 
Wet contact, to me, means mercury wetted contacts which are literally wet with mercury.

Dry contact either means no mercury or a little current that controls a larger contactor, depending on the context of its use.
 

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