Suitable for use in environments with temperatures from -10 to +65C and humidity from 10% to 80%. Adjustable voltage resistor: By rotating the voltage resistor clockwise, the user can easily adjust the device for use with various power sources Includes 5V, 9V, 12V and 24V. This feature allows for a variety of applications in different electronic setups. Protection design: Equipped with reverse polarity protection to prevent damage caused by incorrect battery installation Although the meter not burn out, it not display a reading until the polarity is corrected, thus increasing the durability and usability of the device. Measuring range:Red DC4.50-30.0V, Green DC4.70-30.0V, Blue DC5.00-30.0V Power supply range:No need for additional power supply, directly use the measured voltage as the power supply, the range is the same as above Maximum input:DC30.0V. Note: Input voltage higher than 30V may cause permanent damage! Allowable error:1%; when or equal to 10V, the error is 0.3V; when less than 10V, the error is 0.10 Input impedance: 100K ohms Working current:Red Less than 23mA, green Less than 18mA, blue Less than 13mA Refresh rate:About 300mS once Colour:As Shown Material:plastic Package Contents: 8 x Voltmeter (2 x red+2 x blue+2 x green+2 x yellow) 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.