Tester system for electrical power circuits terminated at an outlet plug receptacle

A tester system which is adapted to be plugged into the outlet receptacle of an electrical power circuit for testing for faults which would affect the capability of the circuit to provide rated output voltage at rated load, whether the output line voltage is within a selected voltage range, and whether the receptable has been properly wired to the high voltage or hot conductor, the low voltage or return conductor and to the earth grounding wire. The tester is enabled on occurrence of a plurality of alternate cycles of the AC power carried by the circuit to connect the line conductors across a measuring resistor of sufficiently low value to draw rated current from the line. An electronic switch, including an SCR, is triggered coincident with the zero crossing of the AC cycle so that a single half-cycle of current passes through the measurement resistor. The measurement resistor may be rated much lower than the rated power. A resistor rated at three watts may be suitable. A comparison and indicating circuit operated synchronously with the trigger pulses compares the voltage across the measurement resistor with a reference voltage derived from the line conductors at no load condition before the measurement resistor is connected across the lines. A timing circuit inhibits the current measurement test components of the tester and enables the voltage range test after the plurality of AC cycles during which the current test is performed.