Make sure the current leakage protection works with the GFCI test function, but be careful not to use it on regular outlets as it may cause the home wiring system to trip. Easily measure outlet voltage, leakage voltage and current with the outlet tester's LCD display and receive clear results even if there are wiring problems. Detect the most common wiring faults in standard and GFCI electrical outlets, including open ground, open neutral, hot/ground reverse, hot/neutral reverse and hot/ground reverse and open ground with this 220V Volt standard 3-wire and GFCI protected. Electrical Problem Checker for AC Outlets. Easily identify wiring conditions in the outlet with the clearly lit red LED indicators and easy-to-understand chart based on LED light results. Quickly identify 6 common wiring errors in standard electrical outlets and GFCI outlets for increased home safety. Features: LED red light test result indicator Clear test result reference chart Pocket-sized portable tester LCD with backlight Function: Three-hole outlet line sequence detection Current measurement Phase voltage measurement (L_N) Leakage voltage measurement (N_E) Ground fault circuit interrupter test Features: Working voltage: 90~250V/45~65Hz. Phase voltage: 90~250V/45~65Hz. Accuracy: (2.0%+2) Leakage voltage: 0~99V/45~65Hz Accuracy: (2.0%+2) Operating environment: 0~40C (20~75%RH) Storage environment: -10~50C (20~80%RH) Altitude: 2000m RCD test: > 30 mA RCD working voltage: 220 V 20 V GFCI test: > 5 mA GFCI working voltage: 110 V 20 V. Note to buyer(s): RCD and GFCI functions do not coexist Set includes: 1 x Pro Socket Tester