IS Barriers Flashcards
What is a non-incendive circuit?
A circuit that does not have enough energy to cause an explosion
What are the 3 components of all intrinsically safe circuits?
Intrinsically safe apparatus (field device)
Intrinsically safe barrier (energy limiting device)
Field wiring
Do active barriers require a ground system?
No
List 3 simple apparatus
RTDs, T/Cs, LEDs
What is systems approval?
Specific field devices, along with specific IS barriers are examined in specific configurations.
What is the max voltage allowed o the safe side of the barrier?
250 Vac
What is the maximum allowable resistance of a ground wire?
Less than 1 Ohm
What does intrinsically safe classification mean?
The device will nor spark or arc and can not store enough energy to cause an explosion
Before you remove a zener barrier’s _______ you must first disconnect ____________.
Ground connections, from hazardous area
You must never cross IS barrier with ___________ because this removes the barrier from the circuit.
Voltmeter leads
What are the advantages of a passive barrier?
Low cost
Small size
What are the limitations of a passive barrier?
infallible equipment ground system
-the need to isolate hazardous-location devices from ground(Ground Loops)
-voltage drops on the current limiting res.
-possible measurement errors due to zener leakage current.
What are the advantages of active barriers?
- High quality ground is not required
- Grounded sensors can be used.
- output signals can be used directly.
What are the disadvantages of an active barrier?
High cost
Designed for specific application
