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Very high ADC value to small load using ADS1232

Vishal Algure
Prodigy 185 points
Other Parts Discussed in Thread: ADS1232

Hello,

We are designing one system with ADS1232 for weight measurement and below is the brief discription about it.

Load cell which has specification of 0.7 mV/V for full scale and we are using 200 gram full scale weight.

We are using 3.3V as reference and 128 is our AFE gain then our input range is limited to 25 mV and measured differential voltage from load sensor for full scale is around 3 mV.

 

But we are facing one issue that we are getting almost highest value for small load cell?

For small load around 20 gram measured ADC count is around 8380461 and after this ADC values restart from zero continoue to increase upto 1100461. So it seems like with no load/tare load we are getting highest value and full scale value we are getting lower ADC value. 

 

This issue observes some time and some time we get correct value for 0 gram to 200 gram.

 

Thanks and regards,

Vishal Algure

  • 0
    TI__Guru** 113765 points

    Hi Vishal,

    The ADS1232 output data is binary 2's complement.  It is possible that you are incorrectly interpreting the results or may have a communication issue.  When looking at your data results it may be best to view the data as it is being retrieved by using a logic analyzer or oscilloscope.  SCLK should be dwelling low and data should transition on the rising edge of SCLK and read at the falling edge of SCLK.

    With no weight on the scale you may see an offset resulting in a negative value returned.  You must sign-extend the negative code value appropriately.

    For troubleshooting you can verify the scope results to your micro code results to see if they are the same.

    Best regards,

    Bob B