Question
Sometimes our measurement setup requires signal integration times of several
seconds, so it is obvious that the low-frequency behavior of the AD210 is of
importance to us. Now we are wondering why the AD210 data sheet gives
specifications only down to a frequency of 10 Hz. From the plot in the data
sheet it appears that the 1/f corner frequency is about 100 Hz (at a gain of
100), and if the noise below really behaves asymptotically like 1/f, the AD210
may indeed be useful to us down to the 1 Hz or 0.1 Hz that we sometimes
require. (The DC offset of several mV is not a problem, as it can be addressed
in the subsequent stage.)
Answer
Back when the AD210 module was designed the Input gain amplifier was a TL082
(from TI) and the graph for the Input noise was based on that part (see
attached graph).
The AD210 modules manufactured currently use the ADTL082 (from ADI) and the
input noise performance should be more like the performance of this part,
however the AD210 datasheet has not changed and we can only guarantee the
specifications in the AD210 datasheet. Although it is possible that the
amplifier could change in the future, we currently do not have any plans to
make a change.
The ADTL082 noise graph is attached