Butterworth Filter PtByPt (Not in Base Package)

Generates a digital Butterworth filter using the sampling frequency, low cutoff frequency, high cutoff frequency, order, and filter type by using the Butterworth Coefficients algorithm.

initialize, when TRUE, initializes the internal state of the VI.
filter type specifies the passband of the filter.

0Lowpass
1Highpass
2Bandpass
3Bandstop
input data is a set of input data.
sampling freq: fs is the sampling frequency. sampling freq: fs must be greater than zero. The default for sampling freq: fs is 1.0. If the value is less than or equal to zero, the VI sets output data to a set of zeros.
high cutoff freq: fh is the high cutoff frequency. high cutoff freq: fh must observe the Nyquist criterion. The VI ignores this parameter when filter type is 0 (lowpass) or 1 (highpass). The default is 0.45. The Nyquist criterion is defined as

,

where is the cutoff frequency and is the sampling frequency. If high cutoff freq: fh is less than zero or greater than half the sampling frequency, the VI sets output data to a set of zeros.

Note  All cutoff frequencies must be less than half .
low cutoff freq: fl is the low cutoff frequency. low cutoff freq: fl must observe the Nyquist criterion. The default is 0.125. The Nyquist criterion is defined as

,

where is the cutoff frequency and is the sampling frequency. If low cutoff freq: fl is less than zero or greater than half the sampling frequency, the VI sets output data to a set of zeros.

Note  All cutoff frequencies must be less than half .
order must be greater than zero. If order is less than or equal to zero, the VI sets the set of output data to an empty scale. The default is 2.
output data is the filtered output data.
error returns any error or warning condition from the VI. Refer to Point By Point Error Codes for more information about these conditions.