... the built-in rechargeable lithium-battery can be used at local test where there’s no power supply. Specific Feature ... 10KHzWorking temperature range: -25°C~ +60°CInternal power source : chargeable lithium batteryExternal power supply :AC 220VMagnetic memory detection with expandable 8 ... on service and preservice of various popeline in the electric power , petrifaction industry,I.e,Cu ,Ti,stanless steel ...