The QTRXL-HD-01A reflectance sensor is a part of the Pololu line of products. It is an all-in-one, programmable, line following sensor. It includes a built-in emitter and receiver board, as well as a low-noise amplifier and analog-to-digital converter. The output of the sensor is a digital, high-resolution signal that can be used to detect and measure ambient light levels, the relative reflectance of the surface of an object, or the width of a line. The sensor is suitable for robotics, robot navigation, and applications where precise photodetection is necessary. It is easy to integrate into a variety of projects, and it is powered by a single 3.3V power supply.