Hi Gene,

I've had a heck of a time with noise when using a 7i90 interface, noise
so bad it destroyed several 7i90's by punching thru the 3.3 volt

That's some serious noise. Do you know where it is coming from? A near field probe is great for finding noise sources. Wrap a dozen turn of wire around an insulating former, say around 2" diameter then wrap some tape around it to hold it in place. Plug the loop into your oscilloscope, crank up the gain and wave it around any suspicious areas. It is usually pretty easy to home in on the noise. With smaller probes you can even trace the noise to a particular area of a circuit board. Noise can come from unexpected places. For instance my inverter has a built in switch mode power supply to power it's logic, as do most inverters. On mine that power supply stuffs more noise back down the supply than the inverter's main drive section!


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