The product uses the Hall principle to detect current. It is recommended to keep at least 15 cm away from magnetic objects during use, otherwise the current accuracy be affected. First-time use method When using or replacing the battery for the first time, you need to correctly set the actual effective capacity of the battery (CAP value in the setting interface). If the effective capacity of the battery is known, enter the setting interface to enter the CAP capacity, and then exit the setting interface. After the battery is fully , and hold the + button on the capacity display interface to set the full capacity. If the effective capacity of the battery is unknown, you need to follow the steps below to enter the setting interface and set the CAP capacity value to a large value, much larger than your battery capacity (for example, what is your estimated battery capacity? The capacity is 20AH, which can be set to 30AH) . Drain the battery pack and set the meter capacity to zero ( and hold the - key on the capacity display interface), then charge the battery pack. After full charging, set the displayed capacity value to the CAP eff-l effective capacity value of the meter. Due to different factory batches, if some parts are different, it have no impact on the product. Colour:Blue Material:ABS Package Contents: 1 * Electricity Meter 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.