Anemometer without moving parts

Somewhere in year 1995 I had idea for anemometer without movable parts. I forgot about that and recently I started building weather station for the vine yard.  Now it’s time to transfer that idea to reality.This is the sketch from that time:

an2

I am working in company HYB in R&D department. My experience with pressure sensors is longer than the anemometer idea (more than 20 years). Our main products are sensors. We have industrial pressure sensors for extremely low pressures. Lowest full scale pressure sensor goes as low as 1mbar (one millibar!). Just for impression: this is equal to 1cm of water column – one cm under the water surface is 1mbar pressure. The model, most suitable for annemometer based on wind pressure measurement is HPSD 3000:

The sensor has 15 bits I2C output  for pressure and temperature via I2C interface. The sensor is available through our distributor or ask directly here.

Main question is: what is the range of the wind pressure at normal weather wind speeds? This is very easy to calculate. The dynamic pressure is the kinetic energy per unit volume of a fluid (a liquid or gas). It can be expressed as:

dynpressure

where

p = dynamic pressure (Pa)

ρ = density of fluid (kg/m3)

v = velocity (m/s)

Normal air density is about 1,2kg/m3 . Maximum practical velocity in Slovenia is about 150km/h, which is about 40m/s. Dynamic pressure of air (using the formula above) at 40m/s is then 976 Pa or about 10mbar. The pressure is proportional to the square of velocity, which means the sensitivity will increase at higher wind speeds. For first approximation, the calibration can be theoretical. We will afterwards calibrate the anemometer using car with GPS or even wind tunnel.

Now it’s time to construct the wind sensor. We will start with four funnels, connected to two differential pressure sensors. Cut the pouring part of the funnel and attach cable inlet as shown in the photo:

funelanemo2

place 3mm pneumatic tubes inside the inlets and secure with the inlet nut.

funelanemo1

 

Further steps (work in progress):

attach sensor to tubes, connect sensors to microcontroller, make first measurements, calibrate, prepare holder for finished sensor, …

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