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Original question:

ADS124S08: Can I use the ADS124S08 to acquire several PT100 RTD?

ADS124S08: PT100 RTD ratiometric measurement if PT100 is open wire then ADC reference is off ?

Youness Mandour
Prodigy 20 points
Part Number: ADS124S08

Tool/software:

Hello,

The RTD measurements with an ADC made with a ratiometric measurements where a single IDAC excitationcurrent source and a the voltage accross the Reference resistance is used as voltage reference for the ADC.

My question is: What happens if an RTD sensor is cut (fails and it become equivelent to an open circuit) ? wouldn't that stop the flow of current, therefore no longer have a voltage reference for the ADC and that would screw up the ADC ?

Maybe I don't understand something.

Thank you in advance.

  • 0
    TI__Mastermind 22815 points

    Hi Youness,

    welcome to our e2e forum and thanks a lot for your interest in our ADS124S08.

    Your understanding is absolutely correct, if you are using only one excitation current source to measure a 3-wire RTD.
    The reference voltage for the ADC will be 0V in that case. The conversion results will then be quite undetermined, but most likely +FS or -FS.
    To detect this fault situation I added the reference undervoltage monitor in the ADS124S08.

    If you want to learn more about sensor fault detection with our ADCs, I can highly recommend the following app note:
    RTD Wire-Break Detection Using Precision Delta-Sigma ADCs

    Regards,
    Joachim Wuerker