The monitor can be widely applied in AC 80-300V mains measurement, such as office, factory, laboratory, household and so on. You can use this item in RV as a way to view voltage to prevent issues with appliances. You can use this item to monitor the voltage of other appliances; when this volt gauge displays too high or too low voltage, you can selectively turn off your appliances or equipment so as to prolong the life of your appliances. Available Range: Widely applied in AC80-300V mains measurement.It enables you to plug in RV to monitor voltage for preventing issues with appliances It's a must to let the children from the product. Do avoid using the product in a damp environment. Potentiometer Adjusting : Just use screwdriver to open the outer coving, then adjust the potentiometer with small size screwdriver. Adjust potentiometer in counter-clockwise when it's excessive voltage, but if display voltage is too low, adjust potentiometer in clockwise. Measuring accuracy: +/-1.5%, +/- 2 word Measuring range: AC 80 - 300V (110V, 220V) Consume power: less than 1W (about every 1200 hours consume 1 kilowatt-hour) Number of digits: 3 digits Potentiometer adjusting : Please use the screwdriver to open the outer case of the voltmeter. Then adjust the potentiometer with small size screwdriver. If the displayed voltage is too high, please adjust potentiometer counter-clockwise. If the displayed voltage is too low, please adjust potentiometer clockwise. Plug Type:EU Plug,it applies to Indonesia, Germany, France, , Italy and so on Material:ABS colour:White Package Contents: 3 x Voltage test meters Only the above package content, other products are not included. Note: Light 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.