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Topic: filter low pass gives me a faster data
Replies: 6   Last Post: Jul 11, 2014 6:06 AM

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inti

Posts: 23
Registered: 5/4/14
filter low pass gives me a faster data
Posted: Jul 4, 2014 9:13 AM
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I'm using a SensorTag which contain 6 sensors. here i'm interessing just for KJ9's accelerometer( data sheet of Kionix KJ9's accelerometer (http://www.willow.co.uk/html/components/com_virtuemart/shop_image/product/OEM%20Component%20Level%20Accelerometers/pdfs/KXTJ9-1007%20Specifications%20Rev%204.pdf)

10hz is a sampling frequency, and i choose a 0.6 as a cut-off frequency (arbitrairy).

My goal is to analyze acceleration's data and isolate a gravity's acceleration. For this reason, i applied a butterworth filter (low and high). Normally i should applied just a low filter, but the problem that gives me a filter's data value > data before applied a filter. for example :

data before filtred :
-0.34
-0.25
-0.31

data after filtred:
-0.08
-0.27
-0.34

(sometimes data after filtred is faster than data before filtred) it is normal?

Thanks in advance for any suggestion



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