Micro Protection with Long Cables
If all you're measuring is a voltage(DC Signal) with the ADC you can probably get away with just putting a small capacitor(~~22nf) to ground to ground along with a voltage follower [a very simple op amp configuration that basically relays a signal while giving the arduino some isolation from noise]. Pretty much any op amp you have laying around will work. An inductor (like one of the ring ones found in computers) in series with the signal wouldn't hurt either.
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