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ADS1263: Can I use separate devices to measure a 3 - wire RTD and multiple thermocouples

Ben Popoola91
Prodigy 40 points
Part Number: ADS1263
Other Parts Discussed in Thread: ADS1262, ADS124S08, ADS1220, ADS122U04

The 3-wire RTD application example (Figure 156, page 114 of the ADS1263 datasheet) shows the RTD solution requires 6 analog inputs to implement. I have a multi-zone furnace application that requires me to monitor 15 thermocouples. Also, I wish to use a 3-wire RTD, as part of my cold junction compensation solution.

Is it reasonable to be able to measure the thermocouples accurately using multiple ADC1263 devices, where one device is dedicated to measuring the RTD, using the application example provide in Figure 156 of the datasheet?

  • 0
    TI__Mastermind 23235 points
    Hi Ben,

    welcome to the e2e forum and thanks a lot for your question.

    You can certainly use multiple ADS1262 or ADS1263 to measure 15 thermocouples plus an RTD for CJC (cold junction compensation).
    However this ADC is one of our highest-end ADCs and it would seem a little overkill to me to use such a device in a furnace controller.
    If you didn't select the ADS1263 because of the high data throughput then I would suggest looking at ADS124S08. This device could measure up to 6 thermocouples or even more if you can tie the 'negative' leads of all thermocouples together.
    In case you want to use a separate ADC for the CJ measurement, then you might want to look at ADS1220 or ADS122U04.

    The evaluation modules of all above mentioned devices provide provisions to directly connect thermocouples and RTDs to them in case you want to evaluate the solution.

    Regards,
  • 0 in reply to Joachim Wuerker
    Prodigy 40 points
    Hi Joachim

    The reason why I have chosen the ADS1263 is indeed because of its high sample rate. Our processes are integrated and driven by Statistical Process Control (SPC) and the thinking, at the moment, is that the ADS1263 will provide us with the high throughput required without the fear of dropping samples. At most 5 thermocouples will be connected to each ADS1263.

    I like the idea of using the ADS1220, as a separate device for CJ measurement. Is there any disadvantage of not using the same device, as the thermocouples?
  • 0 in reply to Ben Popoola91
    TI__Mastermind 23235 points
    Hi Ben,

    thanks a lot for the clarification. I am not sure I understand your fear about dropping samples though.
    How much time do you have to measure 5 thermocouples with one ADC?

    I don't see any disadvantage in using ADS1220 instead of ADS1263 for the RTD measurement.
    You will certainly have to write slightly different firmware to communicate with ADS1220 and the data rates will be different than in ADS1263. Means you need to think about your strategy of how or when you want to read the data from each device.

    Regards,