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Original question:

ADS1247: ADS1247

ADS1247: Schematic Review

Lumina Gui
Genius 3235 points
Part Number: ADS1247

Hi Sir,

Our customer report that they using ADS1247 to connect to PT100 for temperature measurement. But the measured temperature is 10°C lower than the actual temperature (which measured by the temperature calibration instrument). Can you help to review the schematic of ADS1247 for this problem?

The schematic is as follows:

Thanks,

Best Regards

  • 0
    TI__Mastermind 44741 points

    Hi Lumina,

    Has the customer tried testing the system with a precision resistor instead of an actual RTD? This is a good first step to confirm the signal chain is behaving as it was designed before measuring a real RTD. Let me know the outcome of this test and if they get better performance. Then we can try to troubleshoot the real RTD.

    Can you let me know the settings the customer is using?

    • IDAC value, PGA gain, data rate, etc.?
    • Is this a 3-wire RTD that is being measured with 2x IDACs or 1x IDAC?
    • What is the AVDD voltage?

    Also, the input filter on AIN2 and AIN3 is not really doing much. The cutoff frequency is ~800 kHz, so it is not performing any anti-aliasing. I would suggest reducing the filter resistors a bit and increasing the size of the capacitors. You can take a look at the ADS1248EVM as an example: https://www.ti.com/lit/sbau378

    You should also add some nonzero resistance to the reference path.

    -Bryan