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AD7124 different measures with two power modes

Question asked by Arnaud_srett on Jun 14, 2018
Latest reply on Jul 17, 2018 by JellenieR

Hi,

 

I'm using the AD714-4 to measure the temperature using a pt1000.

 

My problem is that with the same configuration, I get two different measures in low or full power mode:

  • Low power mode: 
    • count : 12301575
    • pt1000 resistor : 1096.18 Ohm
    • Temperature : 24.04 °C
  • Full power mode: 
    • count : 12416560
    • pt1000 resistor : 1128.39 Ohm
    • Temperature : 32.09 °C

 

I don't think that this is due to the fact that the full power is more precise because the difference between the two measures is too important. (the correct measure is the low power one)

Does someone have an idea why the ad7124 does this?

 

My registers are in default state except for:

  • The input pins.
  • The reference is external ( 250 µA output from the ADC in a 4700 Ohm resistor = 1.175 V).
  • Gain = 2.
  • Bipolar mode.
  • No internal calibration for gain or offset.
  • Data rate : FS = 2047.

 

Best regards,

 

Arnaud

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