Multifunction DAQ

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Overvoltage protection vs isolation for analog input cards

In the specifications for NI DAQ cards like the NI9238 (AI +/- 500mV), I see overvoltage protection at +/- 30 volts, while Ch-to-ch isolation is at 250 Vrms. Does this mean exposing any of the differential channels to more than 30 V risks damaging the card, or are they ok as long as 250 V is not exceeded?  I have an application where the input voltage to a given channel could spike well above 30 V (rarely and for very short time < 1 s) and want to make sure I won't damage the card. I don't care about collecting data at these voltages since the card saturates at 0.5 V, but would like to avoid having to add isolation amplifiers to protect the cards if they're not needed.

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