Bessel Filter

[Thorsten]

Hi,

I have a problem with the Bessel-Filter. Could it be that the filter
cascades? If I try a selfmade filter 6th order lowpass I get the
coefficents as expected. If I try the bessel filter.vi I get other
coefficents. My problem is, I don't want to make a VI of every order
and filter type I need, so what can I do, to get the 'wright'
coefficents of the bessel filter.vi ?


Thorsten

[Philip_Courtois]

Hi Thorsten,

If you read the documentation for the Bessel Filter VI, it states that after calling the Bessel Coefficients VI, the Bessel Filter VI calls the IIR Cascade Filter VI to obtain a Bessel Filtered X sequence. You can also verify this by double clicking on the Bessel Filter VI.

Please provide me with an example VI that shows how the results differ from your expected values.

Best regards,
Philip C.
Applications Engineer
National Instruments

[Thorsten]

Hi Philip,

how can I post you the VI without knowing your e-mail adress?

Thorsten

[Philip_Courtois]

Hi Thorsten,

You can create a small example and attach it to your comment with the "Attach Files" button.

If you don't want the VI to be public, go to our Technical Support website and request email support. You can include my name in the email if you will.

Best regards,
Philip C.
Applications Engineer
National Instruments

[Rolfe]

Thorsten -

So far as I can tell from the documentation, Bessel Coefficients VI returns coefficients for a cascade filter (the order of the cascade stages is included in the IIR Filter Cluster output). Try using the Cascade->Direct Coefficients VI to convert the coefficients to direct form.

Jason