Cascading Filters
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
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.
Technical support
Hi,
this is already fixed and it works with DEWESoft X1 SP6.