In Reply to: Point of isolation for an isolated Analog Input posted by toysl on 05/16/00 at 9:01 PM:
Your views are essentially correct. A linear optocoupler for the analog signals, if I recalle, can't do much better than ±2% or so of full scale for accuracy whereas a digital representation has no such problem.
However, you have to be careful about the term "surge". While I could agree that optocoupling as early in the signal chain as possible can be helpful, if by "surge", we refer to lighning induced surges as defined in IEC-61000-4, protection will have to rely on more than just the use of optocoupling.
John Dunn - President