I need help. I need to do a anemometer in 3 axis. Basically read velocity, direction in 3 axis (geographic direction and elevation) with 3 ultrasonic sensor HC-SR04. An example:
http://sensovant.com/productos/meteorologia/viento/sensores-ultrasonicos-3d/articulo/Anemometro-sonico-3D-windmaster-pro.html
This doesn’t appear to be a beginner level project, it also looks like an HC-SR04 is an inappropriate place to start, it looks like you need individual transmitters and receivers pointing at each other not a reflective sensor (try a google search of “build Ultrasonic Wind Measurement” for a couple of examples).
edit: These (although there is no data that I can find on driving them) may be more suitable than an HC-SR04 as they are waterproof and I assume this is going to be outside in the rain and the wind. It appears the transmit side wants a 10 Volt peak to peak signal at 40khz (probably with fairly good current drive as it is a fairly high capacitance) the input side may or may not work with the input circuits of the referenced projects.
Peter