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Original question:

ADS1248: how to do calibration for ADS1248 measurement with 3-wire PT100?

ADS1248: how to do calibration for ADS1248 measurement

jkw
Prodigy 100 points
Part Number: ADS1248

https://e2e.ti.com/support/data-converters/f/data-converters-forum/957203/ads1248-how-to-do-calibration-for-ads1248-measurement-with-3-wire-pt100?ReplyFilter=Answers&ReplySortBy=Answers&ReplySortOrder=Descending

sorry for my so late reply.

I do not understand the answer in the previous thread provided by TI expert

" Usually to calibrate an RTD system, you would select 2x high-accuracy precision resistors - typically 1x on the low end of your temperature measurement range and 1x on the high end of the temperature measurement range. You would then apply the IDAC current across these resistors and measure each to get the endpoints of a line that can be compared to the ideal."

can you provide further explanation by picture or something else?

  • +1
    TI__Mastermind 34921 points

    Hi JKW,

    When you measure a Pt100, you are measuring a changing resistance. The calibration method here just takes two of those resistances and calculates a straight line approximation between them.

    For example, if you needed to measure a Pt100 from -100°C to 500°C, then you might select 0°C and 400°C to calibrate. Note that I just randomly chose these values, and you might have to modify them from your specific system.

    A Pt100 at 0°C is 100Ω, while a Pt100 at 400°C is 247.1Ω (note there are different types of Pt100 with different alpha values, so this may be different for the sensors you are using). With this information, choose precision resistors with these values (100Ω and 247.1Ω), place them in your system and take several readings to get an ADC output code. Now you can correlate those resistance / temperature values with the ADC code that you receive, which accounts for gain and offset errors both at the ADC and system level.

    -Bryan

  • 0 in reply to Bryan Lizon86
    Prodigy 100 points

    Bryan,

    Thanks for the further explanation.

    I get your point now.