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Original question:

ADS1248: ADS1248 interface with PT1000 using STM32

ADS1248: PT1000 4 channel 2 wire RTD

ALEX A
Prodigy 20 points
Part Number: ADS1248

Tool/software:

Hi,

     I have designed a 4-channel, 2-wire PT1000 sensor interface using the ADS1248 IC and written the firmware based on the datasheet for my design. I successfully obtained the ADC output for all 4 channels, which is 8388608 in decimal or 7FFFFFh in hexadecimal. Referring to the ADS1248 datasheet (https://www.ti.com/lit/ds/symlink/ads1248.pdf Page 41, under the "Data Format" section), this value appears to be correct when the RTD is not connected to the respective pins. However, when I connect the PT1000 sensor to the corresponding RTD pins, the ADC output does not change. I am unable to identify the issue with my design. Could someone please help me resolve this problem?. ADS1248 schematic.pdf

  • 0
    TI__Mastermind 45071 points

    Hi ALEX A,

    You probably have an issue with your reference voltage if you can only get +FS code (7FFFFFh). The ADC is provides a code that is approximately the input voltage (VIN) divided by the reference voltage (VREF). If VREF is missing i.e. you have selected REFP0/REFN0 as your reference voltage instead of REFP1/REFN1, you are effectively trying to divide VIN by 0. This will give you the full scale code (7FFFFFh).

    Ensure that you have the correct VREF voltage source selected, and that the IDACs are turned on.

    -Bryan