This device is made to be attached to the head of a laser cutter or engraver. From there, it will be able to measure the focal distance from the head of the machine to the material that is being cut. In this particular instance, an ultrasonic sensor is better than an infrared sensor because of the materials that are cut. Some of the materials cut don't reflect infrared waves very well compared to sound waves. So this project tries to make the ultrasonic sound waves as accurate as possible by taking many measurements to accurately calculate the speed of sound in air.