The Ideal Sure Test drop tester. Photo courtesy of Ideal Industries.
Ideal Industries’ Sure Test -- It’s not x-ray vision, but something pretty close. It’s a special tester that puts a 12-amp load across the circuit for a fraction of a second and measures the voltage drop. The voltage drop is proportional to the resistance (actually impedance) in the circuit. So a voltage drop measurement gives an indication of every connection between where I make the measurement and the electrical service entrance.
As I check the voltage drop at receptacle outlets, I expect to see a gradual increase as I get further away from the service entrance. A drastic increase at one point means there’s a bad splice or connection, a damaged wire, or some other source of impedance.
The Ideal Sure Test (www.idealindustries.com) tester is my favorite voltage drop tester, because it does many other kinds of tests. One of these is checking the grounding path impedance under load. This is important with old BX systems where the armor serves as the grounding conductor; the armor and couplings have to be able to pass enough current to clear a fault (by opening the breaker). A polarity tester or a simple continuity test won’t tell you that. The Sure Test also checks the impedance of the hot and the neutral conductors. This guides me in finding the bad connection or splice.