Ultrasonic Anemometer

This page serves as a directory of all my posts and downloads related to my Arduino based Ultrasonic Anemometer.


First Attempt with an ArduinoUno and two separate boards


Ultrasonic Anemometer Shield for ArduinoUno


Trying out new ideas


Standalone Ultrasonic Anemometer with an on-board PIC32


Revised Version on a professionally made PCB




Now the source code for the Ultrasonic Anemometer is available on GitHub: github.com/soldernerd/UltrasonicAnemometer

And the board and schematics: github.com/soldernerd/UltrasonicAnemometerHardware

And the OpenSCAD design for the lasercut structure: github.com/soldernerd/AnemometerLasercut



70 thoughts on “Ultrasonic Anemometer”

    1. Hi Jesse

      Thank you for the flowers. I’ve had several people asking for a kit and I might well do that. But I want to do some more testing to be sure the design works reliably under various conditions…


  1. This is very exciting, thank you again! I haven’t found the part numbers for the 40 kHz transducers … can you tell me which section it is in?

    1. Hi Paul

      I’m not sure if I’ve ever mentioned the precise transducer model. But I’ve just checked my Farnell order: the transducers I’m using are Multicomp MCUSD16A40S12RO, Farnell number 2362677. They cost around USD 5 in small quantities.


  2. hi Lukas,
    i was wondeing if you have a list of the components you used for the proyect

  3. Hi Carlos. Yes, there definitely is as part of the Eagle file. In Eagle, File -> Export -> BOM gets you the bill of materials. And Eagle can be downloaded for free for non-commercial use.

    1. Thank you
      It is one of the most complete works i´ve seen of this kind, really appreciate this!

  4. Ganz ausgezeichnete Arbeit! I hope you continue to delve further into the sensor side of things and discover the reason for the unsuspected small phase shift your described. This is something I’d definitely like to build myself. Do you think it is more responsive to light winds that would a traditional rotational wind cup design? I was hoping to capture very light breezes accurately as well as wind speeds of 5 MPH or more.
    If you ever decide to offer circuit boards for sale, I certainly would appreciate being notified !
    Thank you so much for sharing your efforts with such depth. It is very much appreciated.

    1. Hi Doug

      Thank you for your very encouraging comment. And yes, development will be continued and the open issues will be solved. I’ve just shipped two kits to Argentina where a reader of this blog has access to a proper wind tunel at his university. And I’m full of ideas on how this project can be improved. And once it’s running properly I’d love to sell it as a kit which would give me access to user feedback to improve it further.
      Even as it is now it works very well with low wind speeds. The problem so far has been higher wind speeds…
      Thanks again for your feedback and stay tuned.

      1. I wonder if you’ve given any consideration to the fact that this method of determining wind speed is subject to barometric pressure and temperature changes? Is there a way to compensate in the circuitry and program for such variations?

        PS looking forward to a kit. 🙂

  5. Hi Doug

    Yes, the influence of temperature on the speed of sound is taken care of. The shield includes a quite accurate temperature sensor and voltage reference to measure the temperature. This temperature is then used to correct for the influence on speed of sound.

    Barometric pressure and humidity both have a very minor (compared to temperature) influence on speed of sound and therefore wind measurements. They are not corrected for at the moment.

  6. Dear Lukas,

    just reading up on two-dimensional anemometric wind speed and direction I found your blog plus the notes and software from Carl.

    Besides your two models, there is another model built by Hardy Lau in Germany. Obviously he has been doing extensive wind tunnel tests in the lab and provides some insight on the compensation he needed. For me the setup looks a lot like yours and Carls, maybe you want to contact him.


    I wonder if it may makes a difference to use three transducers in a triangular setup as some of the commercial vendors do ?

    Kind regards,

  7. Hi,
    First of all GREAT WORK!
    But I have a question regarding som components. On the schematics for the arduino shield you have three restistors marked OPT (R15, R21 and R34). What kind of resistors is this?

  8. Hi Martin.
    Thanks for your comment. The OPT stands for optional. When drawing the schematic I thought I might want to put a resistor there (e.g. for some positive feedback around a comparator to add some more hysteris). But I don’t think I ended up using any of them so you can just leave them away.
    cheers lukas

    1. Thank you, I also found 2 “TBD” capasitators (To-Be-Determined” (C8,C13). Any values on them?

  9. I thought I looked at everything but I could not find an area that described the construction of the transmitters/receptors in the four NESW nodes of your annenometer.

    1. Hi Ray
      Are you referring to the way the transducers are kept in place physically? I don’t think i wrote much about it, true. There’s not much special about it: as I see this version as a prototype I didn’t spend too much time to find a perfect solution. I’m using plastic pipes that are made to hold electrical wires. They are cheap and readily available in 16mm diameter which means the transducers fit snuggly without having to attach them at all.
      Cheers lukas

  10. Ok I finished building a copy of your board and tested it with my waterproof transducers. I was expecting what happened but tried anyway. The received signal is almost non existant unless I put the receiver almost in contact wuth the transmitter. This is probably due to the waterproof nature of the transducers. So I can do two things :

    1) Step up the amplitude of the transmitter signal. I will test that with my signal generator ( can go up to 30 Vp-p). The arduino accepts up to 15 V, so let’s see if this changes something. I will need a good driver circuit. But I fear that the 15 Volts will damage the 74HC4052 (because the transmitted signal goes to the transmitter and also to this IC) . Not sure how I can go about it.

    2) Add amplification. I could raise the gain of the two stages or I can put more stages wich is not that encouraging because two stages already occupy quite some space on the pcb. I hope raising the gain will be enough (just have to change the LC tanks) but I’m affraid it won’t.

    Advice ?

    1. Internet references all say that waterproof sensors need voltage swing up to the specified value in the datasheets (140-160 Vp-p) in order to work. So sure, the way to go for this seems to ber a buck converter or a transformer + clamp diodes to protect the rest of the circuit from the high voltage.
      Carl used a waterproof sensor and he didn’t mention anything about that. Reading his schematics, he doesn’t even use the 8V rail to drive the sensor ( the 8V is for the amplifier circuit), just the 5V rail like us. And I don’t see any inductor on his vero board so it seems he didn’t modified the voltage. So unless he reverted back to open-type sensors like the ones you use lfaessler, I don’t understand why his device works.
      Outside, I can’t imagine an open-type sensor would work in the long run. Dust and high moisture level will inevitably make it fail.
      If waterproof = high voltage, it also means security and EMI issues…this is not pleasing :/

    2. Hi Antiath
      Thank you very much for your comment. Just a very short note for now. I’d try changing the amplification. This should be easy by just changing the gain-limiting resistors (R7 and R12 on the schematic) to a lower value like 100 ohms. this should do quite something to the amplification. if you end up at 0 ohms and still don’t have enough gain you can increase the capacitor values of C5 and C10 to maybe 1 micro (instead of 100nano). With the LC tank properly tuned this should give you plenty of amplification.
      Thanks again for trying this design and let me know how it goes.

      1. Ok, I finally had the time to investigate this problem. So I first tried replacing R7 and R12 by potentiometers. First lower R7 to maximum gain. Not enough. So I lower R12 and I quickly reach a saturation point, the gain won’t increase any further even tough R12 wasn’t at the lowest possible value. Frustrated, I just solder two 0 Ohms resistors to see wath happens.

        So I finally see some signal. Progress !

        First observation :
        With a 5 V square wave input in the transceiver and a 20 cm distance between the cells, I get 150 mVp-p of noise and 600 mVp-p of Signal ( so 6 dB). With 15 V square wave, I get 8 dB.

        Second observation:
        an annoying DC offset of 2.46 V ( mean of the amplified signal) . The coupling capacitor isn’t enough to filter out the DC component.

        So the gain is still not high enough, but I also get a dc offset. And addtionnaly, R7 and R12 don’t work as expected ( I used ceramic cap so it shouldn’t be the ESR of the bypass caps).

        I didn’t try changing the LC tanks as I don’t have the parts to do that.

      2. Ok correcting myself a little :

        I managed to remove th weird DC component. I was seeing it on the ZCD, just after the 100 nF coupling cap. I checked on the ENV, after the same cap and the dc part was gone…Seems like a faulty capacitor to me. I replaced the culprit and resolved the problem.

        One less issue to worry about.

      3. Ok I tried replacing the capacitors C5 and C10 like you suggested ( to 1 µF).

        Now it is VERY sensitive 😀 Maybe even too much but now I can make the analog part work. It’s a bit crazy right now, picking up all kind noise but it should be managable and I will try tempering that by radjusting the limiting resistors.

        Thanks for the suggestions 🙂

        A question now : I’m a little familiar with emitter degeneration but I’ve never used an amplifier where there is also a capacitor involved in the emitter part ( only the purely resistive type like this https://en.wikipedia.org/wiki/Common_emitter) . I tought it was just some decoupling capacitor but apparently, there’s more than that. So what’s it doing here exactly ?

  11. Hi,
    Is that a working design right now? If it is yes, what is the range of the wind speed?

  12. Hi Daryl
    Thanks for your comment. Well, it works kind of but I was never happy enough with it to really deploy it. So you’re very welcome to use it but depending on your requirements you might be disapointed.
    But I’m currently working on a totally revised version, both software and hardware wise. I have the first part of it sitting here on my desk and it look promising…

  13. Good Morning! First of all, I would congratulate you for the project done , very complete!
    I have a question for the anemometer. I could use ultrasonic sensors as bringing the HC- SR04, unsoldering the sensors?
    Or necessarily I have to be the MCUSD16A40S12RO?

  14. May be it is my ageing eyes but sections 18 and 19 in the Index appear to be identical.

    Is there a section 18?

  15. First of all congratulations to the first real measurement, what an amazing path, great job!     
    We are in a remote location where our stuff (like windsocks) gets shot at! Instead of attention grabbing mechanical units, we were considering ultrasonics, but they are waaay too expensive. We would be really interested in building some of yours, which designs you kindly made accessible. We could give you remote access to our sensors so you could check them out in our very different conditions. You mentioned you might consider a kit, yes please, please count us in. Would you consider smaller bouncing units, where the path is folded? Or just three sensors? Those would be much more weatherproof. What about Raspberry Pi 3, which is extremely powerful and can be had for $30? Please keep up the excellent work! Thank you!

    1. Hi Jimmy
      I’m already working on a slightly revised board that I will get manufactured professionally. So I hope to soon be in a position to sell some of these, be it as a kit or fully assembled. It’s good to know that some people like you are interested in using these in a real-world application.
      For now I’ll stick to the 4-transducer non-folded design since that’s probably the easiest design to handle. About the RPi 3: For the actual measurements I need a bit more control over the hardware than a fully featured OS is going to allow me. So I’ll continue with the on-board PIC32. But you can, of course, interface it to a Raspberry Pi 3.
      How would you like to Interface to it? Probably not USB since you’ve mentioned that these things are deployed in remote locations…

      1. Thank you for your reply! We do have Pis right at those mechanical weather stations right now, so any interface would be ok. If that PIC32 allows it, and you have a spare opamp, an analog output is always good. Also serial (w NMEA0183 protocol) and/or USB. Serial/USB might have the benefit to maybe change settings down the line.
        In case you kindly offer a kit, the mechanics could be anything, so why not use a folded/reflective designlike this, only 64mm:

  16. What IC was the wiring error to that you mentioned in your latest post? Pin 5 of the digipot?

  17. Hi Lukas,
    I am working with some African Universities in a NORAD-funded research project called WIMEA-ICT designing affordable and robust weather stations to be deployed in Eastern Africa to capture data for the academic communities. We have had a first generation prototype up and running in Bergen since early 2015 (http://wimea-ict.gfi.uib.no/) and are in the process of deploying the 2nd generation in Kampala. Dar es Salaam and Juba. We are planing for a 3rd generation kit design that will deployed by student teams in some 70-100 locations over the next few years.
    We are very interested in getting away from moving parts to increase robustness and would be extremely happy to evaluate your design in tough environments. So, please add us to the queue for kits!
    One of our biggest challenges is power consumption. Each station consists of a local wireless sensor network with at least one node each at 10m measuring wind and insolation, 2m measuring air T and RH, ground level measuring rain, soil temp and moisture, and a sink node measuring atmospheric pressure connected to a gateway with some sort of Internet access. The nodes wake up once a minute, do their measurements and go back to sleep. If we have power enough, we use a raspberry pi with a sink node as an always awake gateway, If we do not have power enough, we use a more power-lean gateway with less functionality and do radio duty cycling.
    Did you measure the power consumption of your design and what do you think about the feasibility of duty cycling?
    Best wishes

    1. Hi Bjorn
      Thanks for your very interesting and comprehensive comment. I would of course be delighted to see my design used in your research project and will be more than happy to supply you with a kit as soon as it’s ready.
      About power consumption: So far I haven’t taken any steps to reduce power consumption yet.The design as I have it running now consumes 44mA @ 12V but most (almost all) of it is used by the PIC which runs at only 3.3 volts. So the real power consumption is something like 150mW. I’m sure that could be lowered significantly in software by using the various power saving features of the pic. I guess the pic could spend plenty of time in sleep mode even when taking continous measurements.
      What precisely do you mean by duty cycling? Turning the unit on and off once a minute is definitely feasable. How much power consumption would be ok for your application?

      1. Hi Lukas,
        Thanks for a quick and very positive answer!
        Any rough time plan for producing kits?
        Do you have a component list so that we can start buying components? We are using gEDA rather than Eagle but I guess we can learn new things 🙂
        Your power consumption is a bit on the high side but it is nce to hear that you see ways to reduce it.
        By duty cycling I mean roughly what you already guessed, powering on and off. There is a little more to it. You need to know how long to wait for the sensor signal to stabilize, how long time it takes to get a sample and to have some sort of synchronization procedure in the sensor network so that the sending node and the sink node are awake at the same time, unless you have an always awake sink node.
        Most of our nodes need a bit less than 20 microamps while in deep sleep and about 20 milliamps during the duty cycle.
        We sample once a minute and the sampling cycle is about a second for most sensors. So on the average about 350 micro amps.
        The sensor node can count pulses, e.g. from the anemometer, even while sleeping, so we transmit the number of pulses that have arrived during the last minute. We started out using an anemometer with a hall element providing the pulses but, to reduce power consumption, we changed to a Reed relay that does not need any power feed.
        The wind vane needs a feed but unlike the case with the anemometer, it can be switched on only during the duty cycle.
        Can you think of any similar possibility to average wind direction/speed during sleep periods using your sensor?

  18. Hi Bjorn

    I was on holiday, hence the late reply. For a component list it’s easiest if you open the eagle files and export the BOM. It’s difficult to commit to a timeline with projects like these but I’ve started working on the revised board that I will get etched. I guess it’ll take another 2 months or so until I have the bords back from the board house and can start shipping them.

    Anyway, be aware that while the hardware works fine from what I’ve seen so far there is a lot of work still to be done in software. I hope that shipping kits will help getting some more people involved with software development and testing.


  19. As a retired eddy covariance research scientist previously involved (since the 1970’s) in developing and deploying Energy and CO2 eddy flux measuring instruments for the UK Natural Environment Research Council, I am very much interested in your project. I’m so electronic expert so most of what you have done goes above my head – but I see applications. In particular I’m looking to use a quadcopter drone to investigate energy fluxes in the near-surface boundary layer of the atmosphere, both vertically and horizontally over different terrain. Your 2-dimensional sonic anemometer carried as a payload beneath a quadcopter combined with a fine-wire thermocouple would provide me with the data to use a method I wrote about in 1991 (see Lloyd et al., 1991. Estimates of sensible heat flux from observations of temperature flucuations. Boundary-Layer Meteorology 57: 311-322). Having said all that – I need to now get down to really reading through what you have done. As I said, I’m no electronic expert but I have assembled many PCB designs – so if you do commercialise the PCB board – I will be in the market. Finally – thank you for your effort, competence and diligence in getting this project to this point.

  20. Hi Lukas,
    Yes, summer has been slow. I will start getting acquainted with agle, your hardware design and BOM while waiting for the boards…
    Best wishes

  21. Hi Lukas!

    I am part of the team that made the custom firmware (http://pljusak.com/nik) for cheap wi-fi routers so that they can read the measurement from meteo stations, and send them to WeatherUnderground and pljusak.com. Pljusak.com is a free crowd-sourcing web page meteorology enthusiasts can share their data. We are also active in sharing the data and helping other similar pages, such as WeatherUnderground, Blitzortung, Flightradar24, …
    However, there is rather poor choice of meteo stations that are both cheap, well supported and available. Therefore, we have started building our own meteo station(s), and your project looks like a nice fit for our needs. Our developers are willing to share their work as Open Source if you choose so.
    Would you be so kind and accept our pre-order for one kit with transducers?

    With regards,

  22. Hi Lukas, Soldering of the two boards I got is well underway and I am trying to print your OpenSCAD design. I assume you refer to the https://github.com/SolidCode/MCAD library but when I try to render I get the message
    Saved backup file: /home/bjorn/.local/share/OpenSCAD/backups/Anemometer_02-backup-DsjG1297.scad
    Module cache size: 2 modules
    Compiling design (CSG Tree generation)…
    Rendering Polygon Mesh using CGAL…
    WARNING: No top level geometry to render
    Is the actual design not included or am I stupid?

  23. Ah, OK, I found that MCAD repo in /usr/share/openscad/libraries/MCAD/screw.scad, thanks,
    However, the result is exactly the same. It seems as if there are only supporting modules in the the you specified in the downloads list: https://soldernerd.com/wp-content/uploads/2014/11/AnemometerOpenSCAD.zip

    This is what I get when trying to compile:
    Saved backup file: /home/bjorn/.local/share/OpenSCAD/backups/Anemometer_02-backup-DsjG1297.scad
    Compiling design (CSG Tree generation)…
    Rendering Polygon Mesh using CGAL…
    WARNING: No top level geometry to render.

  24. Hi Lukas,
    I’m following your project, really good stuff. I’m involved in air speed and other air data measurements. I collaborate also to basicairdata.eu. I read through your posts and I think that we can lend a hand. Just let me know.
    Thank you for sharing!

  25. Hi!
    We are currently building a 3-component Ultrasonic anemometer. And are using your work as a guide .
    We had a few questions regarding the digital circuit:
    – How does 74HC368 actually work? It’s an inverter so it just generates an out of phase Pwm signal. Why do we need this signal?
    – Where exactly have you placed the multiplexer and the decoder is not clear from your writings. Could you shed some light on that.

    1. Hi AparnaJ
      The 74HC368 is really just an inverting buffer. By driving the transducers with the original singal on one leg and the inverted signal on the other leg doubles the signal amplitude from 5V to plus/minus 5V. That’s the reason for using it. My current design uses a 12V supply and a mosfet driver to drive the transducers. It’s simpler and more powerful – the better solution over all.

  26. Hello Lukas,

    Thanks for sharing all the details about your ultrasonic anemometer. I’ve learnt a lot of things reading your blog. I’m a sailor and a software engineer with little knowledge in electronic. I’m using an old mechanical anemometer (3 cups) onboard my sail boat. I’m willing to change it but nowadays this kind of equipements are very expensive (around $800) and with proprietary interfaces to be used by an autonomous boat steering system.

    Like you I was first interested to make it using Arduino to make a prototype but it seems not being energy savy nor being able to sustain the requirements I have :

    – Very Light (< 100 g) (up in the mast lighter is better)
    – Small Form factor (10 cm width, <5cm height)
    – Energy autonomous (solar panel +battery) or consumption < 50 mA (I've 100 A onboard but need to minimize the consumption for the steering system)
    – Up to 10 hertz update rate for wind speed and wind direction
    – At least 1 degree accuracy with a magnetic compass (boats have rotating mast and require external sensors to measure this offset and it is a PITA to calibrate and no need to compensate installation errors)
    – at least 0.1 m/s accuracy on winds from 0 m/s up to 60 m/s
    – Tilt/Yaw/Roll compensation of wind induced by the boat/mast moving (http://kingtidesailing.blogspot.fr/2015/10/correcting-nmea-0183-wind-for-vessel.html?m=1)
    – NMEA output (RS422) to send data to the steering system or wirelessly if running on solar energy (it's a PITA to have to disconnect the system when dismating the boat)

    I'm willing to experiment this with the current design rev b of the autonomous version of your anemometer (without all the bell and whistle I'm looking for) and I wanted to know if the PCB that could be seen on dirtypcb in the shared section was up to date or if any correction was required after receiving the PCB? BTW is the BOM also up to date with your latest work comparison on ultrasonic transducers ?



  27. Dear Lukas,

    Thanks for sharing all the details about your ultrasonic anemometer. I’ve learnt a lot of things reading your blog. I’m a Japanese sailor and a hardware engineer with little knowledge in software.

    I have a question for your Arduino Ultrasonic Anemometer’s circuit. Have you ever made a Ultrasonic Anemometer using PIC16 series? I tried to make that last year, but I didn’t complete it yet. The reason why I’d like to make with PIC16 series is that I have a prototyping experience with that. If you have making a Ultrasonic Anemometer with PIC16 series, please share your schematic PDF and PIC16 series’s source code.

    a.ri.ga.to(Japanese regards)
    Mondo Saito

    1. Hi Mondo
      Thanks for your interest in my project. No, I haven’t designed any charger based on a PIC16 and I have no plans for doing so. However, the PIC18 series is very similar and most code can easily be re-used when upgrading from a PIC16 to PIC18. If you’ve programmed PIC16s before you’ll immediately feel at home with any PIC18.

      1. Thank you for your reply!
        I’m trying to use ATMEL SAML21 series. And I’m struggling with making receive circuit design.
        I have one more question about your anemometer. How much is your anemometer’s resolution in wind speed and direction?

        Mondo Saito

        1. Hi Mondo
          I’m not familiar with the SAM21 series so I can’t give you much guidance here. Concerning the resolution: Native resolution is 1/48MHz = 21 nano seconds. With a sensor distance of 0.2 meters that is about 0.035 millimeters per second. So resolution is almost unlimited. Precision is a completely different story, of course, and depends much on the software.

          1. I’m chasing your trial and error, and feel many difficulties making Ultrasonic anemometer. What drives you to make it?

  28. Hi,

    I was wondering why you used two rails to power the HC4052 multiplexers. You did that to get lower switch resistance?


    1. You need the negative supply if you want to pass negative voltages through the multiplexer. A couple of 10th of a volt are fine without (up to a diode drop) but the gate voltage I pass through one of the multiplexers is plus/minus 3.3 volts so I absolutely need the negative supply at least on that mux.

  29. Hi Lukas,

    I used your design files and BOM to order parts and build boards – just got them assembled last night! I’m having a problem where when I apply 12V, the power supply immediately hits the current limit of 1A. I also tried applying 3.3V to that rail directly, and it steadily climbs until the limit is hit as well.

    Any suggestions on what could cause this behavior?

    One difference is that I’m in the US, so I tried to make a 1-for-1 swap to components I could get through Digikey. I can share the Digikey BOM, if that would help.

    Thanks! Dan

  30. Hi Lukas,

    I have built up a few of the boards using your files and BOM, and I’m seeing some weird behavior. When I apply 12V, the board immediately begins drawing the max current I have my supply set to, about 1A. Same thing happens when I power the 3.3V rail, it slowly ramps up to full current.

    Any suggestions on how to remedy this?


  31. Hi Lukas,

    Just a heads up on what I’ve been doing with this project.
    A little summary : . Apart from the micro choice (using a Teensy 3.6 in my case, so it’s a Freescale 32 bit micro), the design is very close to yours. I use different mosfet drivers and a lm324 to generate 12 V enable signals for those mosfet drivers. The main design difference is the multiplexer part where I use 3 4052 instead of just one. One 4052 for two transducers and then we combine everything in the third 4052. This makes it more easy to manage crosstalk .

    This design has been finished for quite a while now and is pretty stable.

    The signal treatment has been much more difficult than I anticipated. There is tremendous amount of jitter when measuring the phase of the packet. It’s caused but the system not being able to accuratly measure the maximum amplitude ( after the convolution ). So it sweeps back and forth between pulses around the true maximum. But, this is actually managable. The jitter is always a integer number of 25 ms ( a wavelength) so it is possible to detect and substract it. I just have to hope a wind gust will never be speedy enough to make a brutal 25ms or more phase shift between two adc measurements.

    There are more issues I had to take care of in firmware but I’m finally getting stable wind speed measurements. I don’t have access to a wind tunnel but a simple house fan and a 15 euros Uni-t anemometer confirmed the measurements to be at least realistic around 10-20 km/h. I will need to figure out a way to test the device for higher speeds.

    It took a while but I’m getting there 🙂

  32. Hello, it is very nice project!

    I tried about years ago to build sonic anemo (based od Raspberry and 2x ultrasonic range meters (very cheap parts)…) . It works, but limitation is it just work only with basic transducers (that which have no metal or plastic housing), if i use some waterproof it didnt work….

    Please it’s possible to buy or order complete soldered PCB? I have from my last experiments complete anemometer construction (from copper tubes)… I hope maybe finish the goal to measure wind by ultrasonic (outdoor, indoor i get it)…

    It could be perfect for my HD webcam at airfield – http://www.hyvris.cz

    Petr Ludera
    Czech republic

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