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ADS124S08: RTD Measurement Schematic Review

alikaan
Expert 2315 points
Part Number: ADS124S08

Hi,

Please review my schematic. I'll use the "Honeywell - 135-105QAF-J01" RTD for my application. Measurement circuit attached as below.

Also I'll use the ADC0, ADC1, ADC8 and ADC9 for general purpose measurement. ADC3 and ADC2 is for RTD measurement.

Thanks!

7077.ADC.pdf

  • 0
    TI__Guru** 113765 points

    Hi Alikaan,

    It is not clear what your intentions are with the 'RTD'.  You are showing a high-side ratiometric input for a 3-wire RTD, but the sensor you intend to use is a 1M thermistor based on the part number that was given.  The values used in your schematic are not going to work as the minimum IDAC current is 10uA.

    So are your intentions to use a thermistor or an RTD?  If you plan to use an 3-wire RTD then you would need to provide additional information.  I would suggest reviewing the information in A Basic Guide to RTD Measurements.  I would also recommend some additional protection, such as a diode, to prevent an overvoltage on the IDAC2.

    If the measurement is with a thermistor, then you must make sure that the resistance range and the reference resistor chosen will maintain the compliance voltage required for the IDAC.  Also, your reference must also be able to measure the highest value of resistance of the thermistor.  This may be more easily done with a low-side reference and using just a single IDAC.

    Best regards,

    Bob B