Hi, I've been trying to calibrate the ad7730, and I suspect the Zero-Scale System Calibration Mode calibration is wrong (I haven't considered Self-Calibration Mode).
I am using a cell simulator, which at its minimum value reaches the AD7730 the voltage of 0V and at its maximum value it reaches 10mv.
The system calibration process is these 3 steps:
step1: I perform the Zero-Scale System Calibration Mode and obtain offset values.
step2: I proceed with the Full-Scale System Calibration Mode, I get gain values
step 3: finally I continuously read the data and if I can get the data.
Apparently the calibration of the system-full is done correctly, because when reading the maximum value of the simulator the data shows me 65535 (max value of 16 bits), now if the value of the load simulator lowers it to the minimum (0 volts in the ad7730 input) the ad7730 data oscillates between 00E0 (224DEC) when it should be ZERO (0 decimal).
Is it normal that the minimum value does not reach zero?
What am I failing when it comes to Zero-Scale System Calibration Mode?
maybe it could be that the ad7730 is damaged?
When calibrating, is it necessary to do so by deactivating CHOP mode?
When is Self-Calibration Mode necessary?
For this calibration process I am configuring the same filter register value in both calibrations (full and zero Scale System Calibration Mode) - AC activated, chop mode activated, SF = 256, filter register value = 20 00 30 hex
the value of the dac register is 0x20 (it does not subtract or add voltage)