Report Led display Digital Voltmeter question in Projects Q/A Posted June 28, 2004 I am building the same circuit as discussed earliers. I want to attach the meter to a supply and measure the same supply. I find its not possible as the ground and the common is not same. I am attaching the circuit to a 12V supply using a 5V regulater. then monitor the same 12 V supply. How can I do this? Thank you for your help.