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ADS1248: ads1248

siddharth rana
Prodigy 75 points
Part Number: ADS1248


I have  two ADS1248 chip  for 8 differential channels.

using my code i switch between chip selection.

my hardware is designed such a way the same reference register is used for rtd calibration.refp0-refn0.

if i used single ADS chip ,i.e first four differential channel i m getting proper reading,but while using all the 8 channels simulationusly it disturb all my channels output reading.

please elobrate above problem.

  • 0
    TI__Guru* 98135 points
    Siddharth,



    There's not enough detail to adequately debug your problem. If you are able to get one device to properly take multiple readings over multiple channels, then there isn't a reason that you can't do this with two devices.

    What sort of error are you getting? Is the data a little higher or lower than expected? Is the data completely wrong? Does this error affect one device more than another? At this point, I don't have any detail about your system.

    To help debug this, I would need a schematic (or basic schematic) for your board. I would also need a flow diagram of what commands you set and the order of the measurements that you make. I would need to know how the device is set up with all the configuration settings (including PGA, data rate, IDAC and reference settings etc). I also need to know what data is coming out of your device and how it is in error (with raw data from the ADC. At the same time, it would also help to know what the reference and input values are, to compare with the ADC data.

    I've seen many systems that have multiple ADS1248 devices, and they have been operational without errors or problems in output data. I'll just need more information to help debug your problem or even give suggestions.



    Joseph Wu
  • 0
    TI__Guru* 98135 points
    Siddharth


    I haven't heard from you for a week on this problem, were you able to solve your problem reading data for the two ADS1248? As I mentioned previously, if you're able to read data correctly for one devices, there's no reason not to be able to get data for both.

    I'll close this post for now, but if you continue to have problems, post back and we can work on it again. I did notice the other post you have on thermocouple measurement, and I've already responded to that.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 75 points
    Yes with RTD my sampling rate was 40 ksps.as a result my reading were off by 3 to 4 degree Celsius .so adjusting it to 20 ksps .I got exact values.and yes with thermocouple I was missing ground connection .so I M getting some expected reading .thank you
  • 0 in reply to siddharth rana
    TI__Guru* 98135 points
    Siddharth,


    Ok thanks. In that case, I'll consider this post closed. It seems like there might have been some settling issues as you change measurement from channel to channel.

    If you have further questions, feel free to post back.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 75 points
    Hello Joseph Wu,
    Does PGA setting affect my linearity.
    I M using a universal calibrator and injecting millivolt in ADC CHANNEL .
    for PGA setting = 2 my linearity stays upto 30 mv
    For PGA setting = 4 my linearity stays upto 10 mv
    For max PGA = 128 it is upto 1mv .
    Above all other the variation drops to low
  • 0 in reply to siddharth rana
    TI__Guru* 98135 points
    Siddharth,


    This question was asked in an alternate post. I'll close this post and we can discuss the answer there. For reference, the new post can be found at this link:

    e2e.ti.com/.../2701204


    Joseph Wu