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# Advanced | SIFREQ

**FUNDAMENTAL FREQUENCY – [SIFREQ]**

Compute the exact fundamental frequency of a signal.

**CATEGORY**

Advanced

**DESCRIPTION**

Compute the fundamental frequency of the input signal in Hertz [Hz] using an approximate fundamental frequency and using the Brent method

**RESULT VARIABLES AND PARAMETERS**

Result | Fundamental frequency [Hz]. If the function returns zero as a result, this means that the fundamental frequency was not found, probably because the deviation from the approximate fundamental frequency provided is too large. |

Signal | Input signal to perform the calculation |

Freq_Approx | Approximate and initial fundamental frequency in Hz. |

Begin_time | Time at which the analysis of a signal must start. This time is expressed in milliseconds [ms]. This value must be greater than 0 and lower than the size of the acquisition buffer. The default value is 0. |

End_time | Time at which the analysis of a signal must end. This time is expressed in milliseconds [ms]. The value of this time must be larger than the specified begin_time and smaller than the duration of the test. Use the “HUGE” value to specify the end of the test. The default value is HUGE. |

Factor | Multiplying factor for the results generated by the function. The default value of the multiplying factor is 1.0 and has no effect on the results. |

SYNTAX

res = sifreq(input, 60, 0, HUGE, 1)

**CHARACTERISTICS**

Data type support

Double Floating point**EXAMPLE**

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