"Both units ADIS16209 and ADIS 16210 state something which they call "Relative Accuracy" of +/- 0.1 deg.
It is not clear what that means: accuracy relative to what? I guess this brings us back to the readout repeatability…
ADI>> That means that when you move from one orientation to the next, the relative change in angle between those two points with be accurate to +/-0.1 degrees, within the conditions associated with that specification. There are too many variables, outside of the ADIS162xx device's influence to specify these products in absolute terms. For example, 17um of flatness error in the mounting surface can introduce 0.1 deg of error in an ADIS16209-based system. The ADIS162xx devices offer an auto-null function to establish the reference point, which helps translate the relative specification into an absolute accuracy, because it accounts for the mechanical error stack-up, with respect to the gravity reference.
Is it correct to assume both units have the same accuracy? This looks a bit strange since ADIS16210 is three time more expensive…
ADI>> Yes, but accuracy is not the only driver for cost. From a value point of view, the ADIS16210 supports this accuracy over 6x the dynamic range, while only costing ~3x as much: +/-180deg vs +/-30 deg. This requires a third axis; the complexity associated with supporting the third axis adds a disproportionate amount of cost to the materials, assembly, calibration and testing.
Also it is not clear if the units are internally temperature compensated or some sort of temperature correction should be introduced in our software? If yes – what is the correction formula?
ADI>> It is compensated internally, but is that the key information? The conditions associated with the accuracy specifications indicate that they cover a fairly broad temperature range.
There is some wording in ADIS16210 saying that "it does not require any initialization procedure".
Does the ADIS16209 require an initialization procedure? What is it?
ADI>> The ADIS16209 does not require initialization; that statement came into our standard datasheet descriptions after the ADIS16209 was originally released, but before the ADIS16210. The operation and interface are similar in both products: no initialization required, but there are registers which allow you to optimize for particular circumstances.
The ADIS16210 data sheet states that it's "…MEMS sensor elements are bound to an aluminum core for tight platform coupling and excellent mechanical stability" Is this not the case for ADIS16209? What data sheet parameter indicates on this structural difference between the two? "
ADI>> There is no parameter to describe this because the ADIS16209 packaging is completely different from that of the ADIS16210. The aluminum bond is a selling point for the ADIS16210, which comes from this module package style and is part of the expense you refer to above. I am not sure that this is relevant, but in the ADIS16209, the sensor is mounted to a rigid BT laminate structure; no aluminum is used.