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ADS1248 RTD

Akhil Francis
Intellectual 420 points

Other Parts Discussed in Thread: ADS1248, ADS124S08

Hai experts,

I am using four, 4 wire RTDs with 1 pressure sensor . So for this I selected the  ads 1248 but i can not connect all four RTDS and one pressure sensor with ads1248.

which IC i could use for my application?

 Thanks in Advance

Akhil Francis

  • 0
    TI__Guru** 101305 points

    Ahkil,


    One possibility would be to use the ADS124S08 use 8 inputs for the four RTDs. This would require you to stack up pairs of RTDs and use two inputs driving the IDAC currents. A final pair of inputs would be used for the pressure sensor. I'm including a figure below to show how it could be done.


    If you do use this device, you would need to consider several things about the RTD measurement topology. First, the IDAC currents may need to be lower to prevent the stack voltage of the RTDs from being high enough go above the IDAC compliance voltage. Additionally, you need to consider the common-mode voltage of each RTD so that the measurement of each RTD is within the input range of the ADC's PGA. You can find further guidance in the datasheet regarding the PGA. If you bypass the PGA, then your measurement will fall within the ADC input range, but you may lose resolution in the measurement because the RTD voltage range will be smaller compared to the reference voltage.

    If you decide that you can't stack the RTDs, then you'd need to come up with an analog mux to swap out measurements and/or IDAC current drivers.

    The product folder for the ADS124S08 is found below. There link available there for the datasheet.


    I'd note that the topology I showed could be used with the ADS1248 for measuring just the four RTDs because it has two outputs for IDACs that are not shared with analog inputs (IEXC1, IEXC2) but you would still be without a measurement for the pressure sensor that would require a second device.


    Joseph Wu