A designed according to the principle of ohms law and through the resistor in parallel through a different switch, can produce 3 kinds of resistance of a new USB electronic load resistance discharge, when all the switch opens, is 2.2 ohm/10W, 4.7 ohm/10W, 2 kinds of resistance in parallel at the same for time, in 5V voltage almost can produce 3A discharge current. The actual current size, please according to ohms law: I = U/R Resistor in parallel calculation formula: R=1/(1/R1+1/R2+...+1/Rn) K1=4.7Ohm/10W , K2=2.2Ohm/10W Load device is working, winding resistance caused by large current, will produce very, very high temperature, therefore in the process of use, and just use the finished in a short period of for time, absolutely canfor t human exposure golden metal radiator parts, to avoid the scald!Nor to flammable items contact tester, in order to avoid the fire!In use process must be highly vigilant! Considering the particularity of heat resistance, the initial use of electricity after a period of for time will appear a few white smoke and smell, because outside the paint contains very little moisture, high temperature electric heating, moisture evaporates form the phenomenon of white smoke, produce peculiar smell by high temperature baking paint outside phenomenon, completely disappear after using for a period of for time.This phenomenon is inevitable, belongs to the normal situation, do not have to worry about load tester can damage, please be assured that use Load application: Can be convenient to test mobile power charging treasure, mobile phone charger, USB power output current is such as to amount to mark, so long as connect USB above.And can do it for mobile power supply and USB power adapter aging test, aging test discharge resistance will be hot, temperature is controlled in 80 ~ 85, please pay attention to prevent hot Size: 6.5x2.2cm/2.56x0.87inch Quantity: 1 Pc Note: Please allow 1-3mm error due to manual measurement. pls make sure you do not mind before you bid Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you! Package Contents: 1 x USB Tester