CFC Filter Analysis Object (Digital Filters Option)
This analysis object allows you to filter a data set with a CFC filter. CFC is short for Channel Frequency Class.
Filter Type
This allows you to set the filter coefficients. As a digital filter, a 4-pole Butterworth low pass filter is used with a linear phase and specific starting conditions. To achieve the filter, the data must pass through the two-pole filter twice, once forward and once backward, in order to prevent phase shifts.
You can choose from the following filters:
Filter type |
3 dB cut-off frequency |
Stopband attenuation |
Sampling frequency |
|---|---|---|---|
CFC60 |
100 Hz |
-30 dB |
≥ 600 Hz |
CFC180 |
300 Hz |
-30 dB |
≥ 1800 Hz |
CFC600 |
1000 Hz |
-40 dB |
≥ 6 kHz |
CFC1000 |
1650 Hz |
-40 dB |
≥ 10 kHz |
The sampling frequency of the signal must be greater than 6 times the 3 dB cut-off frequency of the selected filter.
Algorithm
The equations for calculating the filter coefficients deviate slightly from each other in the two standards ISO 6487 and SAE J211. Here you choose the standard that you want to use for calculating the coefficients.
Observed Standards
Standard |
Description |
|---|---|
ISO 6487:2000 |
Road Vehicles - Measurement Techniques in Impact Tests - Instrumentation. |
SAE J211/1 MAR95 |
Instrumentation for Impact Test - Part 1 - Electronic Instrumentation |