IDEAL Industries, Inc.

To help you you find bad electrical connections, just use a special tester like the one from IDEAL Industries, Inc. that first measures the voltage at an outlet, then places a brief but heavy load (typically 12, 15, or 20 amps) and measures the new voltage. The amount by which the voltage drops tells you if you have a problem. Anything over 5-6% drop is not good. By testing outlets sequentially on a single circuit, you can generally figure out where any big drop is. (via cool tools)