I am trying to design a 3 1/2 digit 20V voltmeter using the ICL7106 and I was wondering if anybody could help me with a few things: 1. How could I get it callibrated to a max 20V reading? 2. I will be using it as an onboard voltmeter for a variable DC power supply. If I tap the source 18V supply and convert it to +/- 5V will that interfere with my reading (Since I'm indirectly using my measured voltage as a supply to my IC)? I know this is a bit of a specific question but any help would be greatly appreciated. Thanks so much.