Can measuring 50Hz / 60Hz 12V~50Hz/60Hz 380V AC voltage (average); RC Step-down power supply, can connect zero line and fire line directly, no extra power needed; Anti flash touch design; LED working current should be controlled in 20mA, which can lengthen LED life time; Working voltage AC 12V, AC 380V, accuracy / error 1%, Mounting-hole size: 45.5 x 2.5mm; Measuring rate: >/= 200ms/ times 0.6" 3-digit tube; Application range: AC 220V voltage measuring; 22V motor voltage monitor; Inverter output of electricity monitoring and other Ac circuit voltage test; Please note: adopt resistance-capacitance step-down power supply, no isolation, high voltage, require professional electrician to install