Dewe43 and dsi-acc noise at high frequency

Tristan Jones

Posted on 04.03.2017 10:31

Hi just wondering if you could advise me of the expected signal noise using a dewe43a and dsi acc input modules. I have noted a substansial difference in the measurement noise between 100ksamples and 200 with no low pass filtering.

My test setup requires a high logging rate for some specific measurements. As soon as i setup for the high rate channels i saw the previously low noise channels see a significant increase in noise, i ensured the logging rate of each previously setup channel was unchanged. details of noise below. Logger and sensors were not attached to test item they were on my desk as i was setting up the logger for testing.

Logger set to 100ksamples/ Channel set to 100ksamples using a 0.5mV/g accelerometer has approx +/-0.5g noise peak to peak

Logger set to 200k samples/Channel set to 50ksamples, 100ksamples or 200ksamples sees that increase to about +/-10g.

Is this an expected result when increasing the logger sample rate (ensuring the channel sample rate stays the same 100ksamples or less) sample rate from ? And if so what is the best method of removing this noise (eg enable dsi acc anti ailising filter, 30khz low pass filter)?


Tristan Jones

Posted on 05.03.2017 20:15

Hi please see attached logger files.


Logger set to 100k channel 1-3 set to 100k

Logger set to 200k channel 1-3 set to 100k


Attached files:
Tristan Jones

Posted on 10.03.2017 07:41

Hi just wondering if you have any thoughts on this?


Regards

DEWESoft Support
Technical support
Posted on 15.03.2017 10:16

Hi,

I'm sorry that you had to wait a while for our response, but I have some information that I believe will be useful for you. This is the expected behavior because you're using a sample rate divider. What this means is that data is still being acquired with the full rate (in your case 200 kHz), but some samples are then discarded. Because of that, the signal will still contain higher frequencies which show up as an increase in noise (aliasing). To solve this, we have several software filters that you can use.

The latest and probably most effective is the AAF (zero-phase distortion), which can be selected directly through the channel setup interface as a Low-pass filter. We have a new manual which explains this exact predicament and can be accesed on this link. If you have any additional questions please let me know.



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