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ADS1220: How to use ADS1220 measure 2 2-wire RTD?

Will Wang47
Expert 5470 points
Part Number: ADS1220
Other Parts Discussed in Thread: ADS124S08

Hi team,

I get one question from customer. They want to use ADS1220 to measure 2 2-wire RTD. They prefer resistor method, and they find our Tech note "Low-Cost, Single-Chip, Differential Temperature Measurement Solution Using Precision Delta-Sigma ADCs". However the problem is when one RTD is disconnected, the system stop work. So could a good solution to help customer achieve this function?

http://www.ti.com/lit/an/sbaa235a/sbaa235a.pdf 

  • 0
    TI__Guru** 112765 points

    Hi Will,

    Yes, for the application circuit in SBAA235 there will be an issue if there is a wire break.  However, for the Heat Meter (or similar) application, the circuit is localized in that if there is an issue with the RTD the functionality breaks and the unit will have to be replaced anyway.

    So the choice of circuit used is dependent on the use case.  A similar circuit can be used by placing a mux to route the current through individual paths with each RTD connected to AGND.  If higher gain is required, the RTD can be adjusted to the correct common-mode by placing a bias resistor between the RTD and AGND.  A different ADC, such as the ADS124S08 could also be used.  So there are many possible configurations depending on the use case.  Can you share more information about the application?

    Best regards,

    Bob B