Steven Willhoite has been flying his homebuilt Long-EZ since 1998 and has been a design engineer for over 40 years with the last 20 years in avionics product development.
To troubleshoot your system and wring out some wires, you will need to find a good way to make contact between the multimeter test leads and connector contacts.
Aspen Avionics AT300 is designed to be a drop-in replacement for a vertical speed indicator, but you'll get a lot more usable information in the cockpit when you couple it to your GPS; by Rick Lindstrom.