I'm mesure 100 mV from Pt100. I set gane from 1 to 128 and using internal Vref.
I recived such 16 bit digital codes from ADC:
x1 - 5413
x2 - 10819
x4 - 11038
x8 - 21722
x16 - 25780
x32 - 26957
x64 - 28497
x128 - 56952
I do not understand why each successive value of the code is not equal to the previous multiplied by 2?
We are looking into this. We'll get back to you as soon as possible.
Thanks and Best Regards,
FOR undeкstanding, I get 16 bits from 24 bits by discarding the third byte.
Can you provide details on how the ADC is configured?(ex. Buffer enabled, excitation currents, etc.)
Each time that the gain is changed, an internal FS calibration should be performed to calibrate the gain error due to the PGA. Can you repeat your test and include the internal FS calibration when the gain is changed.
Also, take note that the differential input voltage range of the AD7793 is between +/-Vref/Gain. Once this limit is exceeded, the ADC will not perform properly.
So for example, if we have a gain=128 internal voltage reference enabled; given the equation:
AIN=differential input voltage
Gain= gain set in the PGA
Hence, the differential input voltage range of the ADC is limited:
=+/- 1.17V/ 128
Thanks and Best Regards,Chris