Thanks Joseph, I looked over the settings you mentioned and I'm not seeing what I expect. I'm currently in a room that is approximately 80F (26.7C) and the Thermistor measures at 1.529V to GND with a multimeter. My registers are now set like this: Register 0x00 = 0x08 (ID_ADDR_MASK) Register 0x01 = 0x00 (STATUS_ADDR_MASK) Register 0x02 = 0x8c (INPMUX_ADDR_MASK) Register 0x03 = 0x00 (PGA_ADDR_MASK) Register 0x04 = 0x14 (DATARATE_ADDR_MASK) Register 0x05 = 0x1a (REF_ADDR_MASK) Register 0x06 = 0x00 (IDACMAG_ADDR_MASK) Register 0x07 = 0xFF (IDACMUX_ADDR_MASK) Register 0x08 = 0x00 (VBIAS_ADDR_MASK) Register 0x09 = 0x01 (SYS_ADDR_MASK) Register 0x0a = 0x00 (OFCAL0_ADDR_MASK) Register 0x0b = 0x00 (OFCAL1_ADDR_MASK) Register 0x0c = 0x00 (OFCAL2_ADDR_MASK) Register 0x0d = 0x00 (FSCAL0_ADDR_MASK) Register 0x0e = 0x00 (FSCAL1_ADDR_MASK) Register 0x0f = 0x40 (FSCAL2_ADDR_MASK) Register 0x10 = 0x00 (GPIODAT_ADDR_MASK) Register 0x11 = 0x00 (GPIOCON_ADDR_MASK) The readings are consistent. The output does not vary if I heat the Thermistor. Some observations and readings: If I turn the IDAC off as per the dump above (IDACMUX = 0xFF, IDACMAG = 0x00) the raw data reading I'm getting from the ADC is 128 (0x80) If I turn the IDAC off, but leave the IDAC magnitude set (IDACMUX = 0xFF, IDACMAG = 0x05) the raw data reading I'm getting from the ADC is 32896 (0x80C0) If I do not turn off the IDAC and leave it at the defaults I use with the PTC's (IDACMUX = 0x30, IDACMAG = 0x05), the raw data reading I'm getting from the ADC is 8421376 (0x808000) I'm pretty sure that this is related to how my two RTD's are connected to the REF-pins, so here is the full schematic for the ADC + the Thermistor.
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