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TIDM-1019: it is so hard to configure parameter for precise measurement at precise flow under control

Yongseop Yun
Prodigy 20 points
Part Number: TIDM-1019

Hello,

 I have a problem. I can't control error factor.

I think I configured good parameter values. Design center shows great result at 2500LPH around 99,99%/

but When measuring at 40LPH with same parameters at 2500LPH, Desing center shows bad result aroung 90%.

so I configured parameter values(Meter constant, delay AbsToF) at 40 LPH, Design Center shows great reslut at 40 LPH but bad result around 90% at 2500LPH.

I think it is somgthing like symmetry error. how can i solve this problem?

Sorry for my bad english., thank you.

  • 0
    TI__Genius 13660 points
    Yongseop,

    It sounds like you have already done the work for determining the meter constants for high flow (2500LPH) and low flow (40LPH). A single meter constant only accurately supports a certain range of flow. A larger range of flow may require the use of multiple meter constants. The process for calibrating your application to work for both the high and low flow is described in detail in Secton 1.2, Item 11, of the Waveform Capture Based Approach for Ultrasonic Sensing Technology for Flow Metering app report ( www.ti.com/.../slaa837.pdf ).

    To apply what the app report recommends to your actual implementation, you will want to set one of your meter constant configurations as your nominal configuration; for this example let's say you use the configuration for low flow. Then you will want to find the function USS_runAlgorithmsFixedPoint(). Once that function returns you will need to add some code based off of the returned volumeFlowRate to see if the value returned is within the range for "low flow", perhaps from 40LPH to 400LPH. If the returned flow is above that range, then the equation in the app note will be used to calculate what the actual flow rate will be. In the case of the equation from the app report, you know M2 (meter constant for high flow), M1 (meter constant for low flow), and X (un-modified volumeFlowRate). All you would have to do is solve for Y (adjusted volumeFlowRate).

    Best regards,

    Matt
  • 0 in reply to Matt Calvo
    TI__Genius 13660 points
    Yongseop,

    If my previous answer helped resolve your issue please go ahead and select "Resolved" so we can close this thread. Have a nice day!

    Best regards,

    Matt
  • 0 in reply to Matt Calvo
    Prodigy 20 points

    Hello, Matt

    Sorry for repying late. I just have got some different spool.

    Im trying to figure out characteristics of spool in my test bench.

    What I asked for is showing result like pic.

     I set parameters and meter constant at high speed flow around 2500LPH. GUI and EVM(TIDM-1019) show great results.

    When setting water flow slower, error goes up.

    I'm trying to solve this problem with your suggestion.

    Thank you.

  • 0 in reply to Yongseop Yun
    TI__Genius 13660 points
    Yongseop,

    From what I can understand, you seem to have accurate meter constants for both high and low flow. As described in detail in my previous post and in the app report I linked, you will need to utilize both of those configurations if you'd like accurate flow measurements across such a large range. It looks like the high flow meter constant provides >99% accuracy for flow rates above ~800LPH. For flow rates below that, you will need compensate using the meter constant for the lower flow case. The process for how to do that is described above as well.

    Best regards,

    Matt

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