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TDC7200EVM: TOF change

Hsiao victor
Prodigy 10 points
Part Number: TDC7200EVM


Using TDC1000-7200EVM to test the concentration, the temperature and concentration did not change. Why did the TOF value change from 125348 to 125051 after 3 hours?

  • 0
    TI__Mastermind 45315 points

    Hello Hsiao,

    Can you please provide some more information about the configuration?  Are you using 1Mhz transducer with water as the medium?  Do you have a log of the data?  I would like to see if this was a sudden shift or slowly changing over time.  Last, can you provide your GUI configuration?

  • 0 in reply to Eddie LaCost
    Prodigy 10 points
    　 TIME TOF Temperature
    1 09:58 125348 19.99
    2 10:15 125337 20.14
    3 10:58 125319 20.24
    4 11:30 125278 20.45
    5 12:08 125194 21.09
    6 13:33 125015 21.14
    7 14:14 124947 21.15
    8 　 　 　
    transducer 1MHZ 15mm*1mm
    water

    The distance from Transducer to reflector is 90mm
    The medium is water   

      Transducer 1MHZ diameter15mm*thickness1mmm

  • 0 in reply to Hsiao victor
    Prodigy 10 points

    Another test record TOF will also decrease.

    　 TIME TOF Temperature
    1 13:40 124834 20.87
    2 14:31 124823 21.9
    3 15:16 124802 21.1
    4 15:44 124790 21.07
    5 16:08 124782 20.94
    6 17:02 124755 20.88
    7 　 　 　
    8 　 　 　
    transducer 1MHZ 15mm*1mm
    water
  • 0 in reply to Hsiao victor
    TI__Mastermind 45315 points

    Hsiao,

    Thanks for the information.  This ToF decrease seems to be related to the temperature.  In the first data set, the temperature increase by 1.15C.  As the temperature increases, the speed of sound in water will increase resulting in a shorter time of flight.  The link below shows a chart of speed of sound vs. temperature.  You could consider using the temperature of the medium to adjust your ToF calculation.

    https://www.engineeringtoolbox.com/sound-speed-water-d_598.html