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ADS1247 calibration question. PGA accuracy question.

Kristoffer Stork
Prodigy 60 points
Other Parts Discussed in Thread: ADS1247

Hello, I'm about to use ADS1247 to read a shunt resistor.

Normally the ADC will be used with the PGA gain of 16.

This shunt can read ranges of up to 50A and has a resistance of 2mOhm. I have access to a precision 6 1/2 digit current DMM. However, the maximum current is 10A.

Reading the datasheet, it looks like there is separate calibration registers for all the different PGA settings. This leads me to believe that I can use the 64x PGA setting (or higher) to increase the accuracy during calibration at lower current. Is this correct?

- Kristoffer Stork

  • 0
    TI__Guru** 113765 points

    Hi Kristoffer,

    There is not separate registers, but separate internal values used when switching the gains.  If you use a system calibration then you will need to store the FSC register values externally.  However your usage would be correct assuming you are in the correct common mode range.  If the shunt measurement has the shunt connected to ground, then the ADS1247 must be connected to bipolar supplies (+/- 2.5 V).

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 60 points

    Thank you Bob :)

    Also, thank you for making me think twice about bipolar supplies - bidirectional current will be sensed. And bipolar seems like the easiest solution. Creating bipolar supplies is new to me. In a different part of the forum I think these parts were suggested (Can't find the topic). Can you look at my proposed bipolar-supply? (Or should this be posted in the power management section of the forum?)

    Looking forward to getting this circuit to work.

    Sincerely,

    Kristoffer Stork