shockley 0.28 Inch 2.5v-30v Mini Digital Voltmeter Voltage Tester Voltmeter (RED) (1 Pc) Voltmeter  (Digital)

Mini DC Voltmeters - 0.28 inch LED Panel; small in size and light in weight; wire is made of 28awg gauge; install the hole: 23*10 mm approx 2 Connection Methods - 3 wires are connected separately to measure voltage and power(Red yellow is both for pos, black is neg); 3 wires are used as 2 wires, connected to measure voltage(Red and Yellow can be paired for pos, black is neg) Feature - Reverse polarity protection, voltmeter won't burn out if reverse polarity is applied; high precision; low starting working voltage; fine adjustment function Note - Max voltage with yellow and red connected is 40V.To measure greater than 40V (up to 100V) the yellow wire is connected to a separate voltage source that is 40V or less