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Topic: ultrasonic wind sensor (Read 25 times) previous topic - next topic

carl47

Unfortunately I do not know the difference between mine and the commercial units.

I have trawled the net but I can't get even the slightest hint on the internal operation of the commercial units. They keep all their details commercial in confidence.

It maybe that they use cross correlation which seems to be some sort of gold standard.

I will be happy with mine if it compares well with the WMR100.
I run a log of each. Sofar mine is much more accurate at the low speeds where egg cups are poor. At the higher speed there is good agreement.

A wind tunnel would be nice. I no longer have access to such facilities.

carl47

I am using a visual basic program to monitor the operation of the anemometer.

The arduino is programmed with the monitor sketch.
It sends all the necessary data to the visual basic program.
The following is sent from the anemometer about every 3 seconds:

T= 25.04 z= -19000 N= 4633 S= 4754 e= 89 w= -2.59....z= 25467 E= 3929 W= 3848 e= -95 w= 3.47.....Aw= 4 Dw= 126

T.... is the current temperature.
z.... is north-south phase shift -- this is not displayed
N....is the north time of flight
S....is the south time of flight
e....is the north-south transducer error
w....is the north-south wind  -- this is not displayed
....
z....is east-west phase shift -- this is not displayed
E.... is the east time of flight
W....is the west time of flight
e....is the east-west transducer error
Aw....is the actual wind  -- this is not displayed
Dw....is the wind direction  -- this is not displayed





I have found this very useful to road test the anemometer operation.

If you have visual basic you can download monitor.zip from:

http://sourceforge.net/projects/arduinoweather/files/



carl47

#12
Nov 18, 2010, 05:36 am Last Edit: Nov 18, 2010, 05:38 am by carl47 Reason: 1
Operation results:

After 3 months of continuous operation I am happy to move from monitor to full operation.
I cannot give accuracy in terms of % as I do not have access to a wind tunnel.
I can only compare it with my WMR-100 weather station and there is very good correlation. Below 5kph the ultrasonic is much more accurate because of the limitations of the eggcup sensors.
It has been through rain and strong wind gusts and always gives accurate results.
For my amateur requirements the sensor is a success.

Hardware changes:

The body of the anemometer is pvc and a good conductor of heat.
Cooling when there is moisture in the body will result in condensation.
Over a period this can lead to failure of the electronics.
The solution is to ensure that the body is completely sealed from the air.
To be sure I have also used a 100 g sachet of moisture absorbing pellets in the base.

Software changes:

There are a couple of small changes.
One major change is in the running error calculation.
The phase shift is always an exact and robust measure of tof.
So every 300 sample average is used to update the error.
Before I only used the values close to a zero and this was not often enough in a real world wind situation.

download UltraMods.zip from:

http://sourceforge.net/projects/arduinoweather/files/


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