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AD7793 Thermocouple measurement

Question asked by Reza on Sep 10, 2013
Latest reply on Sep 17, 2013 by ChrisD.Rama


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)