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ADS131M08: ADS131M08 How to avoid more gain use for sensor calibration??

Mrityunjai Kumar
Prodigy 10 points
Part Number: ADS131M08
Other Parts Discussed in Thread: ADS1256

Hi,

We are using  ADS131M08 for our new project. We are faced with a list of issues.

 

  1. After 4 gains if we used our readout jumping and my noise level also is high.
  2. Both (ADS1256 and ADS131M08) block diagrams are different means analog input > filter > gain format is followed in ADS1256 but in ADS131M08 analog input > gain > filter section is there. How we control the filter for effective results.
  3. How to avoid more gain use for sensor calibration.

Looking for suggestion.

Thanks,

Vijay 

  • 0
    TI__Mastermind 18900 points

    Hi Vijay,

    Mrityunjai Kumar said:
    After 4 gains if we used our readout jumping and my noise level also is high.

    Higher than what is expressed in the datasheet when doing an input short test?

    If the noise matches the datasheet when shorting the inputs, and then the noise increases when connecting externally, then the external circuits are the source of the noise.

    Mrityunjai Kumar said:
    Both (ADS1256 and ADS131M08) block diagrams are different means analog input > filter > gain format is followed in ADS1256 but in ADS131M08 analog input > gain > filter section is there.

    Not sure what you mean by this, both have the same structure.

    ADS1256:

    ADS131M0x:

     

    Mrityunjai Kumar said:
    How we control the filter for effective results.

    The digital filter diagram shows that OSR, PHASE, and PGA_GAIN are the most important registers to change the digital filter behavior.

    Mrityunjai Kumar said:
    How to avoid more gain use for sensor calibration.

    Noise and maximizing dynamic range (more gain to utilize more codes) are in opposition to another. Depending on bandwidth needs you could implement an external analog filter or front load the gain externally. You could implement a digital filter after receiving the data, such as a moving average (which is effectively another sinc filter). Most of this is external to the device.

    Really the only option to decrease noise is to increase OSR, which decreases your data rate and bandwidth capabilities. 

    Best,

    -Cole