Industrial Engineer · phase 2 of 16 · noun
Dry Contact
Voltage-free mechanical or solid-state contact that requires an external wetting voltage.
The Explain card
- Plain English
- A dry contact is a plain switch with no voltage of its own. Whatever voltage appears on it comes from the circuit it is wired into.
- Example
- The auxiliary contact on a motor starter is dry. The input card supplies 24 V through it and reads whether the contact is closed.
- Why it matters
- Dry contacts can be wired into any voltage the contact is rated for, which makes them the safe way to pass a signal between two systems with different supplies. Feed a dry input with a wet signal and you can tie two supplies together.
- Hook
- Dry means it brings nothing to the party except the switch.
Word knowledge
How the word is built, where it came from, and what it sits beside in memory.
In a sentence
Connect the drive fault relay's Dry Contact to the PLC digital input and verify its state during commissioning.
Why these words
- dry Old English dryge, without moisture modifies contact with an electrical sense developed from the older physical adjective
- contact Latin contactus, a touching names the switching element whose conductive parts meet or separate
Where it came from
- Origin
- English technical compound formed from Old English dryge and contact, borrowed through French from Latin contactus
- Entered the language
- 20th century
- What changed
- Dry broadened from lacking moisture to lacking an applied electrical potential, while contact narrowed from physical touching to a switching junction.
How it is spelled
- Pattern
- The phrase is written as two separate words.
- Pattern
- Dry retains its final y because it is an unsuffixed modifier.
Spelled like
- dry cell
- dry circuit
- auxiliary contact
- normally open contact
Broken into chunks
-
dry
- dryness
- dryly
-
contact
- contacted
- contacting
What it sits beside
Same subject
- wet contact
- relay output
- digital input
- interposing relay
Same shape
- potential-free contact
- normally closed contact
- auxiliary contact
IEC contact symbols
- make contact
- break contact
- changeover contact
relay contact forms
- Form A
- Form B
- Form C
Where it sits in the deck
Phase 2: PLC I/O and Field Signals
Where the controller meets the machine: discrete and analog signals, the wiring conventions behind them, and the field devices that send them.
