This test pen does not require a ground wire or clip, and can be safely connected to electronic control modules, sensitive components, sensors, airbags, etc. It is suitable for maintenance on automobile, motorcycle, bulldozer, road roller, excavator etc. Made of premium quality PC material, which has good performance and strong durability. Built-in battery installation, no need to connect power, which is convenient to use. The innovative design with long life LED light-emitting diode. Measurable voltage range: 0-65V Measurable resistance range: 0-100 K Measurable frequency range: 0Hz-10K Hz Measurable current range: 1-10Amp Operating temperature: 0-60 C (32-140 F) External power supply: Vehicle battery powered 12/24V Package Size: 21*6*3cm Operation Steps: 1. When using, hold the metal piece on the circuit pen tester with one hand, and hold the grounding stud of the car with the other hand. 2. Insert the circuit pen tester into a connector or wire (if necessary, insert into the insulator of the wire). 3. The circuit pen tester will light and beep when a positive voltage is detected. Package list: 1 * Circuit Pen Tester