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Original question:

MSP430FR6043: Anemometer solution by USS

MSP430FR6043: About the anemometer using USS

U-SK
Genius 5840 points
Part Number: MSP430FR6043

Hello,

I am considering to develop anemometer using MSP430FR6043 referring to application note.

required specification is following.

Measurement Range : 0.0～100.0m/s

Resolution : 0.1m/s

Sensor's central frequency : 300kHz

Sensor installation angle : 45 °

Distance between sensors : 60mm

Do you think it is possible to develop anemometer based on application notes with the above requirements?

Are there any concerns?

Regards,

U-SK

 

  • 0
    Genius 5840 points

    Hi,

    Do you have any updates?

    Regards,

    U-SK

  • 0 in reply to U-SK
    TI__Expert 7365 points

    Hi U-SK,

    At a high level, it should be feasible to develop the anemometer solution based on TI's MSP430FR604x parts as indicated in the app note "High-Resolution Anemometers" (https://www.ti.com/lit/pdf/slaa969). The only aspect that is not clear is the range requirement of 0 - 100 m. Can you please elaborate on that?

    Srinivas

  • 0 in reply to Srinivas Lingam
    Genius 5840 points

    Hi Srinivas,

    Thank you for your reply.

    >Can you please elaborate on that?

    Is it mean that you need detail explanation about "Measurement Range : 0.0～100.0m/s"?

    I would like to measure wind speeds from 0.0m / s to 100m / s.

    Is it possible using USS?

    Regards,

    U-SK

  • 0 in reply to U-SK
    TI__Expert 7365 points

    Hi U-SK,

    As soon as I saw "range", I read it as 0-100 m instead of velocity range of 0-100m/s. Sorry for the confusion.

    A 0-100 m/s velocity range with air speed of ~ 343 m/s indicates the DToF can range as much as 110 us with the transducer spacing of 60 mm. The 110 us is derived from (t_UP = 1e6*(60e-3/(343-100))) us - t_DOWN = 1e6*(60e-3/(343+100)).

    This should be feasible with the MSP430FR604x device even though we have not tested or worked with such large DToF values for the gas meter applications. But it should definitely be feasible to meet the requirements with the device.

    With the gas meter application, the DToF that has been tested and required in most residential gas meter applications is closer to 10 us as can be seen in Fig. 22 of the TI Design guide on gas flow measurement (https://www.ti.com/tool/TIDM-02003) -> https://www.ti.com/lit/pdf/tiduej6. This corresponds to about 5 tones even with 500 kHz transducers where each tone has a cycle time of 2 us.

    For your requirements, using 300 kHz transducers, the 110us of max DToF corresponds to 33 tones. You will have to update the application SW to incorporate this range but it is definitely feasible to meet this requirement.

    Srinivas

  • 0 in reply to Srinivas Lingam
    Genius 5840 points

    Hi Srinivas,

    Thank you for your reply.

    I'm considering the anemometer as follows:

    So I think calculation is following.

    t_UP = 1e6*(60e-3/(240.4-100)) =176263ns

    t_DOWN = 1e6*(60e-3/(240.4+100))=427350ns

    DToF=427350-176263=251087ns

    Is my understanding correct?

    Is USS possible to measure 251us ToF?

    If yes, could you tell me what I should modify in software?

    If no, 

    What is the limit of measurable wind speed?

    Is there a solution to meet the specs I posted?

    Regards,

    U-SK

  • 0 in reply to U-SK
    Genius 5840 points

    Hi Srinivas,

    Do you have any updates?

    Regards,

    U-SK

  • 0 in reply to U-SK
    TI__Expert 7365 points

    Hi U-SK,

    I think, at the highest wind velocity of 100m/s,

    t_UP = 1e6*(60e-3/(340-100*cos(theta))) = 1e6*(60e-3/(340-70.71)) = 222.18us

    t_DOWN = 1e6*(60e-3/(340+100*cos(theta))) = 1e6*(60e-3/(340+70.71)) = 146.09us

    You need to consider the component of wind velocity in the direction of the acoustic wave.

    Max DToF = ~ 76.72 us. Using 300 kHz transducers, this corresponds to ~ 23 tones. As I mentioned in the earlier post, this should be feasible. 

    If you use the configuration as in the Application note which had 8 excitation pulses and 300 us of capture, you should not need to modify the SW. Depending on how the signal waveform looks, you might need to increase the capture duration to make sure both the upstream (UPS) and downstream (DNS) signals are captured even at the highest wind speed. 

    Also, you are using 45 degree reflection transducer alignment. One of my colleagues, the author of that App Note, also suggested you can look into a steeper angle that would reduce the max DToF further. For example, instead of 45 degree, if you use 60 degree, the max DToF that needs to be supported will now be ~ 53 us.

    Srinivas

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