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AFE4300: Weight calculation

embedguy 15
Prodigy 50 points

Part Number: AFE4300

I am using afe4300 to measure weight  by connecting load cells. I am able to read adc values coming from the load cell bridge from the adc register. how do I calculate the weight from this? Is their any calculation from  TI for this? Pls assist. 

Thanks 

  • 0
    TI__Genius 12575 points
    Hi,

    You have to find the relation between the ADC counts and the weight by using two known weights placed one at a time.
    Later when unknown weight is placed , by looking at the ADC count we can estimate the weight.
    So from two known weights, try to fit y = mx +c relation where, y = ADC count, x = weight on load cell, m = slope and c = AFE's offset.

    For unknown weight you will have y, m, and c so you can back calculate the x.

    Regards,
    Prabin
  • 0 in reply to Prabin Yadav
    Prodigy 105 points

    Hello

    how i kann know the value of Slop and the AFE Offset and what do you mean with the ADC Count ? do you mean the ADC Values ? or how much Times times we Run it ? please help

  • 0 in reply to David Scheiner
    TI__Genius 12575 points
    Hi David,

    Yes, ADC count means the output of the AFE4300 ( i.e. ADC values, read from AFE).
    You can take few samples , ignore initial samples to remove the settling of the channel ( referred in datasheet as tUP) and take the later ones for calculation.
    The samples taken for calculation can be plotted ( only for first time ) to make sure that there is no settling behavior. Once verified take the average of those samples as use in your calculation.

    Regards,
    Prabin
  • 0 in reply to Prabin Yadav
    Prodigy 105 points
    Hello sir thank you for your reply when i have the 16 bit ADC Value how i can turn it to weight ? i have no idea how i can do that please help or explain us exactly with examples i appreciat that
  • 0 in reply to David Scheiner
    TI__Genius 12575 points
    Hi David,

    Here is an example.
    1) Keep a known weight ( x1) on the load cell. Read the ADC output. store this in y1.
    2) Keep next known weight ( x2) on the load cell. Read the ADC output. store this in y2.
    3) Find the slope as, m = (y2-y1)/(x2-x1)
    4) Calculate the offset as ,c = y2 - (m*x2)
    5) Place the unknown weight (x3) on the load cell as read the ADC output, store it in y3.
    6) To find the unknown weight as x3 = (y3-c)/m

    Hope this helps.

    Regards,
    Prabin