Estimates the Butterworth filter order.
The type of filter that this node estimates.
Name | Description |
---|---|
Lowpass |
Estimates a lowpass filter. |
Highpass |
Estimates a highpass filter. |
Bandpass |
Estimates a bandpass filter. |
Bandstop |
Estimates a bandstop filter. |
Default: Lowpass
Band edge frequencies of the filter, in Hz.
First passband edge frequency in Hz.
Default: 0.2
First stopband edge frequency in Hz.
Default: 0.3
Second passband edge frequency in Hz. The node ignores this input for lowpass and highpass filters.
Default: 0
Second stopband edge frequency, in Hz. The node ignores this input for lowpass and highpass filters.
Default: 0
Ripple level in the passband and stopband of the filter.
Ripple level in the passband.
Default: 0.1
Ripple level in the stopband.
Default: 60
Error conditions that occur before this node runs.
The node responds to this input according to standard error behavior.
Standard Error Behavior
Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.
Default: No error
The sampling frequency in Hz.
This value must be greater than zero.
Default: 1.0 Hz, which is the normalized sampling frequency
Minimum order value that the filter requires to meet the specifications you set.
Low cutoff frequency. The cutoff frequency corresponds to the half-power frequency or the 3 dB frequency.
High cutoff frequency. The cutoff frequency corresponds to the half-power frequency or the 3 dB frequency.
Error information.
The node produces this output according to standard error behavior.
Standard Error Behavior
Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.
This node uses the following equations to estimate the order of a Butterworth filter:
The following table lists the equations for calculating ${\mathrm{\Omega}}_{p}$ and ${\mathrm{\Omega}}_{s}$ for different types of filters:
Filter Type | Equation |
---|---|
Lowpass filter |
${\mathrm{\Omega}}_{p}={\mathrm{\Omega}}_{p1}$ ${\mathrm{\Omega}}_{s}={\mathrm{\Omega}}_{s1}$ |
Highpass filter |
${\mathrm{\Omega}}_{p}=1/{\mathrm{\Omega}}_{p1}$ ${\mathrm{\Omega}}_{s}={1/\mathrm{\Omega}}_{s1}$ |
Bandpass filter |
$\begin{array}{c}{\mathrm{\Omega}}_{p}={\mathrm{\Omega}}_{p2}-{\mathrm{\Omega}}_{p1}\end{array}$ $\begin{array}{c}{\mathrm{\Omega}}_{s}=\mathrm{min}\left(|{\mathrm{\Omega}}_{s1}-\frac{{\mathrm{\Omega}}_{p1}{\mathrm{\Omega}}_{p2}}{{\mathrm{\Omega}}_{s1}}|,|{\mathrm{\Omega}}_{s2}-\frac{{\mathrm{\Omega}}_{p1}{\mathrm{\Omega}}_{p2}}{{\mathrm{\Omega}}_{s2}}|\right)\end{array}$ |
Bandstop filter |
$\begin{array}{c}{\mathrm{\Omega}}_{p}=\mathrm{max}\left(\left|\frac{1}{{\mathrm{\Omega}}_{p1}-\frac{{\mathrm{\Omega}}_{s1}{\mathrm{\Omega}}_{s2}}{{\mathrm{\Omega}}_{p1}}}\right|,\left|\frac{1}{{\mathrm{\Omega}}_{p2}-\frac{{\mathrm{\Omega}}_{s1}{\mathrm{\Omega}}_{s2}}{{\mathrm{\Omega}}_{p2}}}\right|\right)\end{array}$ $\begin{array}{c}{\mathrm{\Omega}}_{s}=\frac{1}{{\mathrm{\Omega}}_{s2}-{\mathrm{\Omega}}_{s1}}\end{array}$ |
where the various $\mathrm{\Omega}$ values equal as follows:
Where This Node Can Run:
Desktop OS: Windows
FPGA: Not supported
Web Server: Not supported in VIs that run in a web application