External power supply: 12V or 24V DC power supply via vehicle battery; Overload protection current: 8A; range: DC 3.5-36V; Line length: 4.5 m; Accuracy: +2%; Rated current: 1-8Amp;Working temperature: -10C-60C;Relative humidity:80%; How to use: 1.Unplug the tester connection wire. 2.The red clip is connected to the positive terminal of the battery, and the black clip is connected to the negative terminal of the battery;thereupon the blue digit shows the current battery voltage value, and turn on the front light; Connect inversely,The voltage value is not displayed,but the lamp is still on. 1:Self-test Before using the tester, please do a self-test to show the integrity of the equipment. 1.The tester button is pressed to the () position, and the LED on the instrument is bright red, indicating the probe output positive voltage. 2.After pressing the tester button to the () position, the LED on the instrument is bright green, indicating the probe output negative voltage. 3.Release the key and contact the probe of the tester with the positive electrode of the battery. At this time, the LED on the instrument is bright Red: indicates that the measured node has a positive voltage. 4.Release the button, put the probe of the tester in contact with the negative electrode of the battery, and the LED on the instrument is bright Green: indicates that the measured node has a negative voltage. 5.The key on the tester is pressed to the () position, and the LED on the tester is bright red, quickly put the probe contacts the negative. Colour:black+blue Material:ABS Package Contents: 1 x Electrical circuit tester Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.