I extracted "Offset Error" specification from ADuC7036 datasheet as below.
Offset Error 1, 3 Chop on, normal mode +0.5(min) −1.25(typ) −3(max) μV
note 1:These numbers are not production tested but are guaranteed by design and/or characterization data at production release.
note 3:Vhese numbers include temperature drift.
From footnote 1, 3, this specification is not performed calibration.
Is it correct?
Offset error is usually 16mV in the customer's system.
However, what is abnormal is also 40mV.
(Customer was using in the "chop on " mode.)
Please be teaching what you think is a something cause.