Zur Fairness gegenüber dem Anbieter wollte ich auch noch mal erwähnen, dass das Gerät dort als Bausatz oder fertig gekauft werden kann zu einem Preis, zu dem man es kaum als Einzelstück nachbauen kann.
http://www.quasarelectronics.com/3168.htm
EPE Ultrasonic Wind Speed Meter Kit £29.75 £25.28 GB£34.95

Vielleicht ist als Einstieg der Kommentar zur Berechnungsroutine interessant:
Code:
;*********** GET WIND SPEED FROM VALUES OF WIND0 AND WIND1

; In still air at around room temp (20^C) when the 2 screen counts are equal,
; the count value (3608 in one version of the prototype) represents a sound speed of 344 metres per second.
; A difference of 1 count between the two counters represents:
; (higher count / lower count) * 344
; e.g. (3609 / 3608) * 344 = 344.09532 metres per sec
; i.e. the sound speed is now 0.09532 faster than above "standard"
; and 1 count represents (rounded) sound speed + 0.1 metres per sec
; Wind speed in this case thus =
; 0.1 * 3600 (seconds in a hour) = 360 metres per hour
; 360 / 1000 (metres in 1 kilometre) = 0.36 kilometres per hour (kph)
; miles per hour (mph) = kph * 5 / 8
; therefore 1 pulse = 0.225mph
; feet per sec = metres per sec * 3.28
; therefore 1 pulse = 0.328 feet per sec
; A 20^C change in temp = 3.5% error from above which is taken as
; insignificant and not correct for.
; N.B. temp change is the main cause of changes in sound speed
; at   0^C = 332 m/s
; at  20^C = 344 m/s
; at 100^C = 386 m/s
; (effects of humidity and barometric pressure are small by comparison)