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Topic: Acoustic Resonance Anemometer Design Guidance/Review (Read 2 times) previous topic - next topic

Qeynes


I can't respond to the physics but I can tell you to use the 74HCT4046 or better an 'old' signetics NE561 or 2.


Bob, thanks for your reply.  After reading your suggestion, I ordered 3 of the CD74HC4046AE from Digi-Key, but only now noticed that they were the CD74HC4046AE, not the CD74HCT4046AE.  Do you know if there will be a significant performance penalty because of my mistake?



I am very dubious about the whole physics of the project.
You are only using one phase locked loop and I don't see where that gets you. Drive the transducers with a differential signal not a single ended one.
Normal wind vectors are measured by three othagional paths and a time of flight, with temprature measurement sepratly as an adjusting factor.


    Thanks for your advice on driving the transducer.  I've attached an updated block diagram which I believe corrects that particular error.  I would be very grateful if you could take a look at it to check if I altered the diagram correctly.
    Much of the inspiration for this project comes from this https://docs.google.com/a/google.com/viewer?url=www.google.com/patents/US5877416.pdf patent.  According to the patent, creating the vertical standing wave is very helpful in increasing the amplitude of the signal and thus helpful in increasing the signal to noise ratio.  I also worry that if there is no standing wave the reflections from the cavity walls will start to mess with the signal.  That's why I have that single PLL controlled by the transducer directly above the signal transducer.  I think it will compensate for temperature effects on the speed of sound when setting the frequency that will make a vertical standing wave (at 72 F the 4th harmonic of the cavity is 40 kHz, but the harmonic frequency changes with temperature).
    One of the primary objective of this anemometer is for it to be small, so I decided to forgo the 3D wind vectors to make the system more suited to for use on a mobile robotic platform.  Once again, thanks for your advice.

Qeynes


You do realise this has been done and has extensive documentation on the internet ?


Well, I have seen, for example, carl47's amazing project. http://arduino.cc/forum/index.php?topic=53569.0


However, while carl's project and the others I have found like his are excellent as stationary weather stations, they are quite bulky and operate on different principles than the anemometer described in my previous post's patent reference.  In fact, my attached transducer layout looks fairly large relative to comparable commercial sensors, I now plan to halve the distance between signal transducer and the x&y transducers to 2.605 cm.   I failed to mention in my initial post that the the anemometer is intended to be able to be used on mobile robotics platforms (sorry), like one used by the Olin Sailbot Team (to which I have no connection):


To date, the only documentation I've found of such sensors has been the patent, this simplified manufacturers explanation:
http://www.fttech.co.uk/acu-res-technology/,
and pages 6 and 7 of this paper on robotic sailbots:
http://cadair.aber.ac.uk/dspace/bitstream/handle/2160/3103/IRSC.pdf?sequence=2.
It was that last link that really gave me the confidence to pursue this route; they appeared to get fairly decent results for with a rudimentary phase detector and without adhering very strictly to the patent description.   I hope that by following the patent more closely and using ICs designed for phase detection I'll achieve similar and maybe better results.

If you know of some documentation that augments the 3 links that pertained to acoustic resonance anemometers, as opposed to simply ultrasonic anemometers, I would love to hear it.  I was getting close to using bing to get find information.:smiley-eek-blue:

greywolf271

Quote
If you know of some documentation that augments the 3 links that pertained to acoustic resonance anemometers, as opposed to simply ultrasonic anemometers, I would love to hear it.  I was getting close to using bing to get find information


As a matter of fact !!!!...........
I have been looking at stationary anemometers myself for a number of weeks and this is a fairly good link I came across.
Now I have not checked the majority of your links that you placed on this forum, I'm just (trolling !) through these forums looking for other information and happened on your question by chance.... so if you've already come across this reference, sorry for wasting your time....

http://www.technik.dhbw-ravensburg.de/~lau/ultrasonic-anemometer.html

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