What is use of barrier & isolator in automation system and where they should be used?

How can be the Digital I/O's and Analog I/O's isolated?

Give the difference between Barriers and Isolator?
and place of use?

 

Barriers are used in Hazardous locations to power Intrinsic Safe instruments. The barrier will reduce the available loop current to a level that cannot produce a spark.

An Isolator is used to connect signals of different common mode voltage for example a transmitter signal may be referenced to +24 whereas the DCS may be referenced to ground.

You can also have an isolator that is designed for use in Intrinsic Safe circuit.

Regards
Roy

 

The barrier or isolator provides only a part of limit in energy, it ensures that current or voltage fed to the hazardous area from a source in the safe area is insufficient to cause ignition.

You must have either a passive barrier or an isolator between the hazardous and non-hazardous area to protect against faults in the safe area.

As stated above, a barrier is a Passive device but Isolator is an active device and needs power.

You can find more detailed in "MTL" or "Pepperl + Fuchs" web site.

Hope this helps you,

Vahid

 

Roy gave good advice. We use barriers for intrinsic safety wiring purposes. Isolators see many uses including splitting signals between a field device and DCS + PLC AND connecting an output from one equipment to another.

Here are additional links for more details.
Barrier basics from P&F:
http://www.am.pepperl-fuchs.com/pdf/documents/2006-application-guide.pdf
Analog Isolator basics:
http://www.miinet.com/whatsnew/articles/interactive_signal_interface_ins_and_outs.pdf
Digital Isolator basics: refer to the P&F literature above.

MTL, P&F, Moore, Phoenix, Action Instruments, and many others are useful solution-providers for the devices you are considering.

JC

 

You can download MTL's Technical Paper on the difference between barriers and isolators here:

http://www.mtl-inst.com/support/tp.htm

Steve
syates at mtl-inst. com