I was surprised some time ago when I found out that the modern wind speed measuring devices work without moving parts. I had expected them to all have these spinning ping pong ball halves.

To do it without moving parts, they are for using for example ultrasound. These devices have pairs on transducers, placed 10-20cm apart and the device then measures how long it takes for the sound to pass through that distance.

https://en.wikipedia.org/wiki/Anemometer#Ultrasonic_anemomet...