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TDC1000-TDC7200 The maximum frequency of measurements per second

Maksim Proh
Prodigy 30 points


 We produce flowmeters for measuring pulsating fluid flow. Pulsation produced by the pump amplitude of 30% of the mean flow frequency of 50 Hz For the correct result we need to perform measurements with a high repetition rate
Is it possible to chips TDC1000-TDC7200 realize flowmeter for solving this problem, a frequency measurement 250..1000 second?

Thank U!

  • 0
    TI__Mastermind 21685 points

    Our flow expert will get back to you on this. thanks.

  • 0 in reply to Vishy Viswanathan
    Prodigy 70 points

    Hi,

    I would like to increase the measuring cycle. This means more measurements per second. Only 100 ms as a minimum in the GUI 1.0.9.0 has the trigger update FREQU. I need but 10 ms, 1ms would be better.

    I can find no source code for the GUI. The text file is only in HEX-code.

    Can you easily lead to outside the trigger or is it only in the GUI.

    High frequencies are very important for my application.

    Greetings

    Frank

  • 0 in reply to user1029675
    TI__Mastermind 21685 points
    Frank,
    Trigger update frequency is generated and controlled in firmware. GUI only sends user selected value but in firmware you can override and select any faster update freq.
    Timer1 (see functions timer1_A0_init() in file timer_queue.c) is used to generate a 100ms interval and this is then used to generated other intervals (200ms, 300ms, etc.). You can modify this function and Timer1 A0 interrupt service routine to generate your own interval.
    When you go to smaller intervals you have to optimize and make sure up/down flow measurements as well as any data output on UART is done within the selected interval.
    Regards,
    Vishy
  • 0
    TI__Expert 3350 points
    Maksim,
    The acquisition rate you specified translate to a range from 1 sample every 4 msec to 1 sample every 1 msec.
    To determine if you can achieve the best case sampling scenario in your application use the following relationship:
    Ts = TOFF + TOT + TDN + TOV + TUP +TOF < 1 msec
    TS = Total time for one conversion
    TOFF = Time from "standby" state to "operating" state (if power cycling is used)
    TOT = Time from on state to trigger
    TDN = Time of flight downstream
    TOV = SW overhead time from last STOP pulse to trigger for upstream sequence
    TU = Upstream time of flight
    TOF= SW overhead to put TDC in the standby state
    So assuming 100 us time of flight in water application in some flow condition, no power cycling, there is approximately 800 us time budget left for the SW overhead, the most significant of which is TOV.
    Therefore the sampling rate of 250 sps to 1000sps is doable in this case if you keep the software over head to a minimum (under 800us) . But you need to workout the details about your system and see if the total time adds up to less than 1 msec.

    Regards,

    B. Mirshab
  • 0 in reply to Vishy Viswanathan
    Prodigy 10 points
    I would also like a faster sample rate. Can someone from TI fix the GUI so 0.5ms Trigger sample rate is possible and works with the graph and file saving functions.
  • 0 in reply to John Muehlebach
    TI__Mastermind 21685 points
    John,

    Sorry, we don't have plan to update the software for such high trigger speeds.

    Thanks,
    Vishy