Protecting Digital inputs of PXI6508

[Didier Lambrecht]

Normally input high values of 5V are read into my PXI6508. Suppose by accident 80V is connected to that input. In that case I want to design a protection that stays intact where I don't have to replace optocouplers. I've come up with something but maybe you have something better in mind.

Thank you,
Didier

[rgharrison]

Hi Didier,

Your voltage divider scheme in theory should work. However, 5V signals wouldn't register as logic high. 1/16th of 5V is much less than 2.2V which is the input low voltage threshold.

You would have to move to a voltage clamping scheme using diodes to get it to work but you need to make sure that the circuit components you use are within tolerance for voltage and power. There are also manufacturers that sell clamping circuits also. Anyway, hope that helps. Have a good day.

Ron