Installation Guide: correct wiring as per the included diagram. Use isolated power supply up to 20V or a common cathode DC-DC converter. the black thin wire is insulated to prevent short circuits. Includes button functions for easy data management and error correction related to component aging or temperature variations. Multi functional OLED display voltage and current meter Due to different batches, there may be differences in product appearance and printed text, which not affect use, Manufacturer: Akfldms