EN
 
English
Italian
French
German

Cascading Filters

nick arran

Posted on 18.11.2014 15:37

Hi,

In dewesoft X SP5:

I need to filter some data with a 2 pole low pass filter formed from two different single pole filter sections.

Seems a simple thing:  just feed the output of one single pole IIR filter to the input of another IIR filter....  but it doesn't always work.

Generally adding a second filter to the cascade does work, but once the original filter is altered the output of the second filter becomes a constant 0.  Changing the filter back to the original specification doesn't make it work again.

EG:  

The first filter is a 2 pole 2.4Hz low pass

I add a second filter (a 1 pole 0.5Hz IIR) to filter the output of the first filter .. the output of the second filter is OK

I modify the original filter to a 1 pole 2.4Hz LP IIR filter; now the output of this first filter is OK, but the output of the second filter is 0.

I return the original filter to a 2 pole 2.4Hz filter; the output of the first filter is still OK but the output of the second filter is still 0.

Bug? Fix?  Anyone have the answer?

Thanks

Nick A

nick arran

Posted on 20.11.2014 10:55

More information .... in fact the above problem is only present in Post Maths.  

I created a new setup file on a PC with the dewe-43 plugged into it, and everything works fine.

But when attempting to create a filter cascade in Post Maths (ie reprocessing an old data file) it doesn't.

DEWESoft Support
Technical support
Posted on 06.01.2015 08:38

Hi,

this is already fixed and it works with DEWESoft X1 SP6.

Login to reply to this topic. If you don't have account yet, you can signup for free account .
This website uses cookies to ensure you get the best experience on our website. Learn more