This is a voltage detection sensor module for your Arduino, AVR, PIC or other microcontroller project.  This voltage sensor connections to the DC positive and negitive of the cirucuit you would like to monitor via the screw terminals.  The three pin header is connected to a analog-to-digital input of your microcontroller.  This module will detect voltages between 0.0245V ~ 25VDC and produce a corresponding anolog voltage on the output pin connected to your A/D input.  This module operates on 3.3 – 5VDC.  This is the perfect module to add voltage detection to your Arduino project!