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EVM430-FR6043: ADC Capture and dTof Calculation

Kons
Prodigy 60 points

Part Number: EVM430-FR6043

Hi Experts,

I have the following question about the ADC Capture: 

Q1: What is the reason for the signal curve in the marked region in picture 1 ?  This occurs even without transducers connected (picture 2)

Q2: Does the ADC capture show the direct translation of the voltage signals of the transducers, or is the result of the cross correlation shown there? 

Also, I would like to know if the calculation of the dTof and the absTof are independent of each other. I already reviewed a lot of documents about the calculation process. If I understand it correctly, the absTof and dTof calculations are based on different principles. While the absToF is calculated via a threshold in combination with the Hilbert transformation, the calculation of the dToF is done via a cross correlation. So if I measure the absToF with a high standard deviation, does this also affect the standard deviation of the dToF or are they independent?  

 

Thanks for help 

Best Regards,

Konstantin

  • 0
    TI__Genius 10060 points

    Hi Konstantin,

    I think that this artifact is due to the simulation pulse that excites the transducer.. What is your ADC delay set to?

    The pulse capture you have looks pretty clean. Typically it is no problem to ignore the initial part of the capture (by increasing the delay) to remove any artifacts.

    I will have to think about your second question.

    Regards,

    Evan

  • 0 in reply to Evan Lew
    Prodigy 60 points

    Hi Evan, 

    I intentionally chose the delay too short to show the artifact. Thanks for this tip anyway. So you mean the artifact is caused by the square pulse produced for the transducer excitation and has nothing to do with the transducer signal itself ? 

    When I increase the number of pulses, the artifact shifts to the right, so it appears "later". Is this due to the longer time needed to generate the pulse? 

    Regards,

    Konstantin

  • 0 in reply to Kons
    TI__Genius 10060 points

    Hi Konstantin,

    Sorry I'm behind, I'll respond on Monday.

    Evan

  • 0 in reply to Evan Lew
    TI__Genius 10060 points
    Kons said:
    When I increase the number of pulses, the artifact shifts to the right, so it appears "later". Is this due to the longer time needed to generate the pulse? 

    Yes, this seems correct to me, the more pulses in the initial (stimulus) pulse train the longer total time it will take.

    Regarding your other question:

    Kons said:
    So if I measure the absToF with a high standard deviation, does this also affect the standard deviation of the dToF or are they independent?  

    Since both measurements rely on the same data, I would think that more signal to noise ratio would improve the standard deviation of both measurements.

    Regards,

    Evan

  • 0 in reply to Evan Lew
    Prodigy 60 points
    Kons said:
    Q2: Does the ADC capture show the direct translation of the voltage signals of the transducers, or is the result of the cross correlation shown there? 

    Thanks, for your answer, can you maybe give some more information about this ? 

    Regards,

    Konstantin

  • 0 in reply to Kons
    TI__Genius 10060 points

    Yes, ADC capture shows ADC codes, there is not pre-processing preformed.

    Regards,

    Evan

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