dc 4.5 v-30 v digital voltmeter 0.56 "led 2-wire voltage volt meter panel gauge

description: -this fullmeter s wiring is simple, it only needs two wires, the red wire is connected to the positive pole, the black wire is connected to the negative pole. -there is protection when the wires are not properly connected, the electrical circuit won't be bummed. -this fullmeter does not need external drive work power, it can work with measured voltage, the working voltage s range is 4.5-30 v. to achieve the measurement accuracy, these voltmeter s automatically move the comm