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ADS1248: Schematics review.

Naser S.
Genius 11605 points

Part Number: ADS1248

Team: Customer is using several ads1248 in 4 wire configuration to measure a resistor.
The different devices differ in their result. They would like to know, how they could correct that.

They´re using the configuration as in figure 1 one this site: http://www.electronicdesign.com/analog/improve-noise-immunity-rtd-ratiometric-measurements

Let me know and I can send you exact configuration and schematics for review. Thanks.

  • 0
    TI__Guru** 113765 points

    Hi Naser,

    For configuration and schematic review you can contact me directly or through :

    pa_deltasigma_apps@ti.com

    Each ADS1248 will measure differently for a number of reasons which requires calibration.  Some of these reasons include variation in IDAC current, tolerance and actual value of the reference resistor used, as well as offset and gain error of the ADS1248. 

    For each ADS1248 the offset can be self-calibrated by the device by issuing a SELFOCAL command.  The ADS1248 is trimmed for gain error so that may not be the significant issue.  Most likely the difference that is being seen is due to the variation of IDAC output and the differences in the reference resistor values.  To calibrate this effect, the ADS1248 cannot do this directly so the customer will have to create a routine in the firmware to calibrate and then use the calibration data to adjust or correct the conversion result.

    Best regards,

    Bob B