Crash CFC digital filter (chncfcfiltcalc)

[rhunzinger@exponent]

Need some clarification on the chncfcfiltcalc routine. Is it a 2 pass Butterworth?
We have some data that has a 4 g shift at the beginning of the data when filtered w/ CFC_60, and endpoints. Switching to zero-magnitude somewhat alleviates the problem. However, this is a 'program' that other 'non-programming' engineers use, and they should not have to recognize this data tail off at the beginning of the file, enter the SUD and change to Zero Magnitude. We have not seen this tail off as typical in the past. Any suggestions?

Thanks,

Bobby

[Walter_Rick]

Hi Bobby,
The Butterworth filter is a 4 pass.
For further information I attached a document which describes principals of the Crash Analyse functions. More detailed infos you find in the SAE J211 (Appendix C) in which the 'zero-magnitude' (FIGURE C3 and C4) is explained.

I hope this answers your question.

Greetings

Walter

[pgstein]

Sorry to dig up an old thread, but I am trying to implement a CFC 1000 filter in LabVIEW 2009.

The pdf states:

3 dB limit frequency : 1650 Hz

Stop damping: -40 dB

Sampling Frequency: at least 10 khz

From another thread I got the following information:

for CFC1000  IIR, Butterworth, order 4, Force zero phase, Lowpass, Filter freq = 1650 Hz

How would I implement this? I am using a Digital IIR Filter, what would the filter parameters be?

Thanks,

Paul