• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 46 subscribers
  • Views 781 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ADS1256: ADS1256

Nuri Basar
Prodigy 20 points

Part Number: ADS1256

Hi,

I use ADC1256 to measure loadcell(wheatstone bridge) sensor.

Inıtialize fetures ;

data rate : 100 SPS

gain : 64

Vref : 1V

buffer : Disable

avdd : 5V 

dvdd : 3.3V

I use 4 differential channels. For example, firstly, I power on and apply necessary initializing settings. Then, I read channel 1 and count is 1605818 . It is stable and maximum mobility  200-300 count. It is suitable for me.

However, I  power off then again on , this count value is 1608563. Difference between these two values is 2745 count. 

How can I solve this problem?

Best regards,

Nuri Başar

  • 0
    TI__Guru 58841 points

    Hi Nuri Basar,

    When you say "count is 1605818", is this the code (in decimal) you are receiving from the ADC? Or is this some other value that you have manipulated from the ADC code?

    What happens if you power off the ADC again, after receiving the count of 1608563? Does it go back to 1605818?

    Do you calibrate your system each time you power up the ADC?

    -Bryan

  • 0 in reply to Bryan Lizon86
    Prodigy 20 points

    Hi Bryan,

    "count is 1605818" is decimal value that receiving from the ADC. If I power off/on a few times , the value go back to its original states.

    At the first, I send SELFCAL command in initializing function, but it is not solve my problem. I closed it in my code.

    my initialize settings:

    1-)WAIT DRDY

    2) Send Command (RESET);

    3) Delay 1000 ms

    4) Send Command (SDATAC);

    5) Write Register (DRATE_REG) //100 SPS

    6) Write Register (ADCON_REG) //set gain 64

    7) Write Register (STATUS_REG) //set buffer disable

    8) Delay 500ms

    9-)WAIT DRDY

  • 0 in reply to Nuri Basar
    TI__Guru 58841 points

    Hi Nuri Basar,

    Have you confirmed this is not an issue with the sensor itself? In other words, have you tried using a precision source e.g. lab equipment, a small battery, etc., to see if the issue is replicated?

    You can also try removing the sensor and shorting two ADC inputs together to measure the ADC noise. The ADC noise can then be compared to the datasheet (see Table 4 for RMS noise with buffer = off).

    Let me know what is the outcome of these tests

    -Bryan

  • 0 in reply to Bryan Lizon86
    Prodigy 20 points

    Hi Bryan,

    Thank you for helping.

    We produce the sensors ourselves. All sensors are tested with necessary test procedures. I will try your suggestions.

    Is my initialize settings true or not? Could my problem be caused by this?

    -Nuri 

  • 0 in reply to Nuri Basar
    TI__Guru 58841 points

    HI Nuri Basar,

    I don't see anything obviously wrong with the settings you have provided. Nor is there any obvious reason why the code would shift after being powered off and the back on. Or why it would return to the previous "good" code after a few more power cycles.

    Initially I thought that this might be a settling issue, where you are not waiting long enough after power-on to start taking data, so some of your analog circuitry might not be settled. But according to the initialization routine (which I assume is run after every power cycle), you are waiting almost 2 seconds before taking data. This should be plenty of time, but I defer to you to check your schematic / board to make sure

    Let me know the results of the tests I suggested.

    -Bryan