I have a question about Gain Adjust Register of AD5421.
The Gain Adjust Register of AD5421 cannot adjust the value upward.
Why isn't there upward adjustment value?
Hi Mr. K,
If you require a higher swing, you could use one of the higher ranges (e.g.3.8mA-21mA) and adjust the gain downwards as you require.
This is to ensure retention of the accuracy specs of the part.
Thank you for your reply.
I think that the gain error has the possibility of deflecting to a plus side or a minus side from the ideal as shown in figure.
I think that it cannot adjust the gain error by this register when the gain deflects the plus side.
Because this register has only the adjustment value of the downward.
Is this idea correct?
Gain error is a measure of the span error of the DAC. It is the deviation in slope of the DAC transfer function from the ideal and so an adjustment of the gain will affect every code's equivalent analog output.
Taking the case of positive fullscale and substituting into the 4-20mA transfer function, we can see that the max value for "Gain" is 65535, thus not allowing an expansion of the output beyond the fullscale 16mA value.
The idea of the Gain adjust facility is to be able to calibrate out any extra system gain if required.
The expansion cannot be adjusted by this gain register when the gain error is lower than 16mA.
(@4-20mA mode, output is full-scale)
I want to know the reason why the gain register doesn't support the expansion adjustment.
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