Is the resulting dynamic resolution in SR0 12bit? Olov
Yes, that is correct.
Why map to 16 bit? It´s a waste of space and bandwidth. Olov
I understand where you are coming from. The primary reason is to capture the bit growth associated with the averaging and different range options available in the REC_CTRL2 register.
I don´t see the logic in that but that may be me, we tried various REC_CTRL2 settings with same result. It´s just the FS setting. Olov
I agree that you need to have averaging (from the lower sample rate settings) in order to have bit growth to capture. To your question, if we just kept the range at 20g, it would seem like we would run out of digital resolution before we reached the lowest setting in the AVG_CNT register, wouldn't we?
No that´s not how it works IRL. We checked at the lower ranges to verify behaviour, 1g I think and it overloaded at 65000 + counts still having 12 bit resolution as can be seen as we entered a lo freq sinus signal and looking at the statistics where you can see "lumping" at every 32 count steps. It can even be seen that 2 steps miss match and don´t have exactly 32. So the finding is that the 12 bit resolution is mapped to 16 bits at every range setting. There are no single bit jitter either that would otherwise expected. You would not be thinking of a 3-axis ADXL001 in a package so we could A/D convert as we like? In that case we are looking at AD1974 or AD176-2 would you suggest one of those or another? Olov
I see where you are coming from, but still believe that there is value in what is offered, even if not in your situation. We appreciate the consideration but we are not considering this type of product at this time.
With respect to your last post in this discussion, I wanted to add one more thing. The bit growth doesn't come from the range reduction, but the averaging filter that is associated with the AVG_CNT register. Have you seen the 12-bit resolution observations hold true at the sample rate settings you have been using? At SR6, I would have expected to see dither into the 16-bits of the register, regardless of the resolution level.
We have tested some settings and they gave the same 12 bit result. I will try SR6 at some time. Olov
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