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ADS124S08EVM: Multiple RTD configuration with single Rsense

Sarumathi R
Intellectual 480 points
Part Number: ADS124S08EVM


Hi Team,

Please clarify the below quires,

1. Shall we use the same Rsense resistor value for different type of RTD(like PT100, PT1000 and PT500)

for example if we configured the channel 1,2 and 3 for sense resistor, channel 4 and 5 for PT100 2-wire RTD, channel 6 and 7 for PT1000 2-wire RTD, channel 8 and 9 for PT500 2-wire RTD then shall we able to calibrate/process the all the three type of RTDs(PT100, PT1000 and PT500) with same value of Rsense(lets say 1k or 2k) or we need to put different Rsense resistor for each type(like for PT100 the Rsense will be 1k for PT1000 Rsense will be 2k)?

Kindly help on this.

Thanks in advance.

  • 0
    TI__Guru 54046 points

    Hi Sarumathi,

    Typically you can use 1x sense resistor with different RTD types, though you will have to change the IDAC and gain settings to get the best performance out of your system. If you have RTDs with very different nominal resistances - say, a Cu10 and a Pt1000 - it might be challenging to get the best performance with just 1x sense resistor however. But for Pt100 to Pt1000, this should certainly be possible.

    You would generally want to set the sense resistor to be ~5-10% larger than the largest resistance you need to measure, which in this case would be the highest temperature for the Pt1000. Then you can scale the gain and/or the IDAC value for the other RTD types. Just make sure to consider the min/max input voltages on the ADC's analog pins and VREF inputs.

    Here is a link to our RTD cookbook for lots more information on performing RTD measurements with our ADCs:https://www.ti.com/lit/an/sbaa275/sbaa275.pdf?ts=1607522918643&ref_url=https%253A%252F%252Fwww.google.com%252F

    -Bryan