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I am working with some analog +/- 10V a/d conversion cards that are part of a larger process system and I've got a question about the way they describe their maximum allowed voltage based on the table below.

The answer in this one case is probably to contact the vendor but I'm interested in knowing if this terminology is common enough that I would expect to see the same description elsewhere.

Specifications

  • Input Signal Ranges: +/- 10VDC
  • Maximum permanent allowed overload (no damage): +/-12.5V

Should I be interpreting that as anything beyond +/-12.5V is potentially damaging OR is it anything overloaded by 12.5V beyond the valid input signal range +/-(10+12.5)V?

Obviously I wouldn't expect a valid A/D conversion of a 13V signal but based only on their specifications would I be in the range of potential damage?

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1 Answer 1

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I would assume the worst case is +-12.5V absolute is damaging.

Since your input can only measure up to +-10V anyway, you should use back to back zeners to allow your input to deviate within that while protecting your input to under the 12.5V value.

The input itself may however include that kind of protection anyway. In which case, you should limit how much current the signal can over-drive it with. Read the documentation for the cards carefully, and if need be, contact the manufacturer.

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