So in our master thesis, we need to measure a distance between two nodes with ultrasonic waves. So I was wondering, what ways can you measure distance.


Should I use a measure tape, an Ultrasonic Distance Meter or a Laser Distance Meter?


What is the problem with a measurement tape, it is not very accurate and it doesn’t ease the work of the user. Why do we still use it then, first of all it’s very cheap and easy to handle and use. It has also a lot of shortcomings, like how to measure something when object are in the way. Also it is difficult to measure long distances when you’re by yourself.

File:Tape measure colored.jpeg

So how can we overcome these limitations, let us use a more “intelligent” measuring system. These digital measurement tools use electronics to ease the work of the user, like knowing how to use Pythagoras.

A Laser as well as a Ultrasonic Distance Meter, sends out a burst and waits for the signal to reflect back from the object and then measure the time it took. The only difference is what kind of burst it is, a laser uses a burst of light. Logically an Ultrasonic meter uses an ultrasonic sound burst to measure distance. There are some differences between light and sound, light is more directive and travels in a straight line, at a velocity of 299 792 458 m / s which is dependent of the used wavelength and  medium. While sound travels with a speed of 340.29 m / s and is dependent of humidity, pressure and temperature because it needs a medium to travel through. It propagates less directive, it sends out a cone (like you see on the picture underneath).

beam width

In general are laser distance meters more accurate, this because they use more focused bundles so they have a bigger range and light is less dependent of external factors. But the components to measure this are more expensive because they need to work at higher clock frequency. We use Ultrasound in our thesis, because we only need a range of about 10 meters, which is viable for Ultrasound and find it beneficial that that a transmitter sends out a cone of ultrasound, because then multiple receivers can receive the transmitted burst. It is also less sensitive to the time errors because sound propagates at lower speed, so the time error of the electric signal that needs propagates trough the cable is more negligible.


What would you choose to measure distance, the Laser or Ultra Sound? You can read this small paper, because it is a good comparison and my post is also based on it.