Last Modified: January 12, 2018

Computes the frequency response and the coherence and returns the results as the real and imaginary parts of the averaged frequency response.

This node calculates the frequency response of the channels in the stimulus signal against the channels in the response signal according to the following table:

Stimulus Signal | Response Signal | Results |
---|---|---|

One channel | One channel | One output. |

Multiple channels | One channel | The first channel in the stimulus signal against the single channel in the response signal. This node ignores the remaining channels in the stimulus signal and returns a warning. |

One channel | Multiple channels | The single channel in the stimulus signal against the first channel in the response signal. This node ignores the remaining channels in the response signal and returns a warning. |

Multiple channels | Multiple channels | The first channel in the stimulus signal against the first channel in the response signal, the second channel in the stimulus signal against the second channel in the response signal, and so on. If the number of channels in the stimulus signal and response signal do not match, the node ignores the remaining unmatched channels and returns a warning. |

Empty | Empty | If either the stimulus signal or the response signal is empty, the result is empty and the node returns an error. |

A value that affects the output coefficients when **window type** is Kaiser, Gaussian, or Dolph-Chebyshev.

If **window type** is any other type of window, this node ignores this input.

This input represents the following information for each type of window:

**Kaiser**—Beta parameter**Gaussian**—Standard deviation**Dolph-Chebyshev**—The ratio of the main lobe to the side lobe,*s*, expressed in decibels

**Default: **NaN—Causes this node to set beta to 0 for a Kaiser window, the standard deviation to 0.2 for a Gaussian window, and *s* to 60 dB for a Dolph-Chebyshev window

Time-domain window to apply to the signal.

Name | Value | Description |
---|---|---|

Rectangle | 0 | Applies a rectangle window. |

Hanning | 1 | Applies a Hanning window. |

Hamming | 2 | Applies a Hamming window. |

Blackman-Harris | 3 | Applies a Blackman-Harris window. |

Exact Blackman | 4 | Applies an Exact Blackman window. |

Blackman | 5 | Applies a Blackman window. |

Flat Top | 6 | Applies a Flat Top window. |

4 Term B-Harris | 7 | Applies a 4 Term B-Harris window. |

7 Term B-Harris | 8 | Applies a 7 Term B-Harris window. |

Low Sidelobe | 9 | Applies a Low Sidelobe window. |

Blackman Nutall | 11 | Applies a Blackman Nutall window. |

Triangle | 30 | Applies a Triangle window. |

Bartlett-Hanning | 31 | Applies a Bartlett-Hanning window. |

Bohman | 32 | Applies a Bohman window. |

Parzen | 33 | Applies a Parzen window. |

Welch | 34 | Applies a Welch window. |

Kaiser | 60 | Applies a Kaiser window. |

Dolph-Chebyshev | 61 | Applies a Dolph-Chebyshev window. |

Gaussian | 62 | Applies a Gaussian window. |

Force | 64 | Applies a Force window. |

Exponential | 65 | Applies an Exponential window. |

**Default: **Hanning

A Boolean that specifies whether the node restarts the selected averaging process.

True | Restarts the averaging process. |

False | Does not restart the averaging process. |

When you call this node for the first time, the averaging process restarts automatically. A typical case when you restart averaging is when a major input change occurs in the middle of the averaging process.

**Default: **False

Settings that define how this node computes the averaging.

The mode this node uses to compute the averaging.

Name | Description |
---|---|

No averaging | Does not use averaging. |

Vector averaging | Uses vector averaging. |

RMS averaging | Uses RMS averaging. |

Peak hold | Uses peak hold averaging. |

**Default: **No averaging

Weighting mode for RMS and vector averaging.

Name | Description |
---|---|

Linear | Uses linear weighting. |

Exponential | Uses exponential weighting. |

**Default: **Exponential

Number of averages to use for RMS and vector averaging.

If **weighting mode** is Exponential, the averaging process is continuous. If **weighting mode** is Linear, the averaging process stops after this node computes the specified number of averages.

**Default: **10

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 mode this node uses to compute the frequency response function (FRF).

If you know that noise, which does not propagate through the system under test, infiltrates the input or output signals, you can select the method for computing the FRF to minimize the measurement error.

Name | Description |
---|---|

H1 | Minimizes errors in the result when extraneous noise contaminates the output signal. |

H2 | Minimizes errors in the result when extraneous noise contaminates the input signal. |

H3 | When noise contaminates both the input and output signals, H1 and H2 provide the lower and upper bounds of the true frequency response of the system. In this case, select H3, the average of H1 and H2. |

**Default: **H1

Real part of the averaged frequency response of the input signals.

This output can return a cluster or a 1D array of clusters.

Start frequency, in Hz, of the spectrum.

Frequency resolution, in Hz, of the spectrum.

Real part of the averaged frequency response.

Imaginary part of the averaged frequency response of the input signals.

This output can return a cluster or a 1D array of clusters.

Start frequency, in Hz, of the spectrum.

Frequency resolution, in Hz, of the spectrum.

Imaginary part of the averaged frequency response.

A Boolean that indicates whether the number of averages this node completed is greater than or equal to the specified number of averages.

True | The number of averages this node completed is greater than or equal to the specified number of averages. |

False | The number of averages this node completed is less than the specified number of averages. |

** averaging done** is True if **averaging mode** is No averaging.

Number of averages this node completed.

Error information.

The node produces this output according to standard error behavior.

Standard Error Behavior

**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.

Coherence of the averaged frequency response of the input signals.

This output can return a cluster or a 1D array of clusters.

Start frequency, in Hz, of the spectrum.

Frequency resolution, in Hz, of the spectrum.

Coherence of the averaged frequency response.

**Where This Node Can Run: **

Desktop OS: Windows

FPGA: This product does not support FPGA devices

Web Server: Not supported in VIs that run in a web application