I am studying to design with your 12 AD7657s that have same lot number.
So I met the error problem.
Why is this trouble happen?
Please give me your good advice reason why?
When I input 10V dc here, your AD7657 converted the result 8111 to 8131digit.
This have higher 50 or 60 digit than a theoretical value.
Also input -10V dc here, the converted result was -8111 to -8131 digit.
And when I put this on high tempereture area, the convert value have higher around 100 digit than a theoretical value.
Of cource AD7657 have the positive full scale error +/-0.61%.
This means 2^14 * 0.0061=99digit, correct?
If so, 50 or 60 digit means within the full scale error, and no problem correct?
In this case, the reason why is come from Vref drift, I thought.
But Vref come from extrnal source and stable.
At in front of analog input(T/H AMP), there is a buffer OPAMP as voltage follower such as your good OP07.