I've a problem with the AD7793.
when i try to measure a thermocouple using AD7793 at the sample rates faster than 16.7Hz, then an slow rate sinusoidal harmonic noise appears in the waveform.
For Example, if the temperature is 500 deg C, Then the measured waveform with AD7793 is a sinusoidal line around 480 to 520 deg C periodically.
Input Stage Filter is: 1k ohm, 100nF, 10nF, Like the example.
Reference Voltage is: ADR441ARMZ
Gain is: 32
"Vbias and boost" is enabled
"BurnOut" is disabled
Speed: (6) fADC=39Hz and tSETTLE=48ms
Input: Thermocouple Type J (Also by Calibrator)