Overcurrent protection for 4-20mA inputs

I didn’t exactly understand your problem. But if your current source is standard, no worries about it. You should just use TVS diode on input to protect from transient voltages.

alec_t said:

I haven't trawled through the old thread, but has anyone suggested a current-limiting diode (or two)?

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Someone suggested a voltage-limiting zener.

A zener would be better, since you can have better faith in the leakage currrent.
A current limiting diode in series sounds actually better solution, since it does not have the possibility to crete a false reading.