This great little DC-DC converter has an inbuilt red LED 3 digit voltmeter which can display either the input voltage or the output voltage, depending on the position of the pushbutton switch. There's a small LED on the board that lights when you are viewing the input voltage, so there's never any confusion.
Input voltage: 4.5 - 24VDC
Output Voltage: 1 - 20V (Adjustable)
Output current & Power: 2A/20W
Conversion efficiency: Up to 90%
Operating temperature: Industrial grade (-40 ℃ to +85 ℃)
Connection: Screw terminal
Dimension: 48mm (L) x 32mm (W) x 18mm (H)