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When to use MCU vs External ADC in RTD Application

John Lee76982
Prodigy 55 points
Other Parts Discussed in Thread: LMP90100, ADS1148, ADS1248

Hello,

I am interested in RTD temperature monitoring, and it seems that RTDs are typically coupled with an external ADC rather than using the MCU's. I am wondering what is the rationale for not using the included adc on a given MCU, and what are the conditions for the MCU's ADC to be 'good enough'?

Thank you for your response in advance.

John

  • 0
    TI__Guru** 113765 points

    Hi John,

    RTDs require excitation and often times gain is needed.   It is not just a matter of 'good enough' but precision and accuracy over a specific range.  Also, a ratiometric measurement can give you better results with respect to noise and drift.  If the micro can deliver the desired results, then great.  Often times though it will not.  A device like the ADS1248, ADS1148 and related products like the LMP90100 family can provide excitation current as well as the ADC.  

    Best regards,

    Bob B