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TDC1000-C2000EVM: Adjusting the period of the recieved Echo

Alexander Konradi
Prodigy 50 points
Part Number: TDC1000-C2000EVM
Other Parts Discussed in Thread: TDC1000

Hello,

I am currently working on a projekt where I am tried to measure the level of water in a Tank and concentration using the  TDC1000 EVM and Transducer. So far the setup and understanding of the GUI are working fine, but I have following problems.

1. The calculated distance with the input of the TOF doesnt match my measured fluid level. I am always off by about 2-3mm from my measured level and the more fluid the less this offset seems there seems to be. I have tried to change the parameters to get a more accurate calculation but havent been successful. Is it possible to delay the time of the recieved echo or change another parameter to get a more exact reading?

2.When measuring with one set of parameters from 5cm to about 19cm, I get a sudden and repetative signal loss. How come this happens? Is the echo signal to strong or to weak to create a Stop signal?

I hope that I will be able to get some answers.

Alex

  • 0
    Prodigy 50 points

    Hello,

    the first problem has been solved, now there is just the problem with the signal loss.

    Kind Regards

    Alex

  • 0 in reply to Alexander Konradi
    TI__Mastermind 31655 points
    Hi Alex,

    This is most likely the signal being too low to trigger the stop. You can adjust the Echo Quality Threshold and the PGA gain through trial and error to achieve a more stable signal, but the best method is to monitor the COMPIN signal with an oscilloscope while making adjustments.

    If the signal is still dropping out after adjusting these settings, please save the GUI register config file and post it here along with some scope captures of the COMPIN signal.

    Regards,
  • 0 in reply to Scott Cummins
    Prodigy 50 points

    Hello,

    thank you for your answer. I have attached the COMPIN, START and STOP signals to an oscilloscope and am recieving a very good and accurate signal on the oscilloscope, without any sign of signal loss.

    I came upon the idea of adjusting the TRIGGER UPDATE FREQ in the setup tab by changing it incrementally from 500ms to 800ms and recieved a very good signal with this method measuring from 185mm to 300mm. The problem is that im not sure if this is a legitimate solution to the problem or if it can be solved otherwise. With the settings in the TDC1000 Tab I am getting a very good signal on the oscilloscope, but adjusting the TRIGGER UPDATE FREQ enables the GUI to recieve a clear and stable signal.

    Please give me your input on this method.

    Kind Regards

    Alex

  • 0 in reply to Alexander Konradi
    TI__Mastermind 31655 points
    Hi Alex,

    It appears this is just a problem with the USB communication to the GUI. If changing the GUI update frequency fixes this, then it is a valid solution. Just to make sure it is not a problem with the actual echo data, try doing a 128 cycle average (NUM_AVG on the GUI) and make sure that your GUI update period is longer than the time it takes to make those measurements. If the resulting averages are very stable, then it is likely just a USB communication problem.

    Regards,
  • 0 in reply to Scott Cummins
    Prodigy 50 points
    Hi,

    we assumed that that might be the case but you just clarified the problem. Thank you for that. Nevertheless I have another issue. I can't seem to be getting stable measurements if I do the same measurements with the same parameters for multiple measurements over the course of a couple of days. I'll do a measurement with great results, then do the same measurement the next day and get a reading with a level measurement that is off by 1mm-2mm. This is an unacceptable case and I am wondering if it has something to do with the problem of the USB Connection.

    Thank you for your time and help.

    Regards,

    Alex
  • 0 in reply to Alexander Konradi
    TI__Mastermind 31655 points
    Hi Alex,

    Does the level change fluctuate both over and under by 1-2mm? Are you comparing the inaccurate measurement to the previous measurement or to a measurement with a ruler or something? If the tank you are testing with is open, is it possible that water is evaporating and resulting in a level change?

    Regards,
  • 0 in reply to Scott Cummins
    Prodigy 50 points

    Hello,

    Im am comparing the calculated level to a scale that is on the tank itself and the calculated level is always 1-2mm under the measurement of the scale, never over. The scale has increments of 1mm.

    The Tank is open but the fluid is filled up every day and we are measuring a range from 50mm to 350mm, therefore the error can't come from evaporating water. The offset of 1-2mm under the level of the scale is pretty much constant throughout the measuring range and like I have stated before, one day the reading is correct and one day it is off. 

    Regards, Alex