Exact frequency

When you press the Setup button on new activated Exact frequency line, the following Exact frequency setup window will open:

Math_FDA_ExactFrequency_Setup

The Exact frequency supports multiple input channels.

For detailed information about basic settings of the input and output channels see -> Setup screen and basic operation.

The Exact frequency is a very nice procedure for determining the exact frequency of the signals. Even with lower sampling rates which don’t allow methods like period measurement and even with signals with not that clear level crossing this method will work very nicely.

The method is based on finding the best fit to the theoretical sine wave. It can measure millihertz accurate with sampling rates only a few kHz and a low block size. The method works best on the signals close to the pure sine wave. It will search and lock to the highest harmonic component in the signal.

In the right area of the window are - Output settings - Calculation parameters- with:

  • Block size - Block size defines the calculation interval. The resulting frequency will be updated with this speed, but we need to take care that this interval will be longer than 10 measured periods of the signal.
  • Use amplitude threshold - Amplitude threshold defines the minimum amplitude where the signal is still calculated. If the RMS of the signal is below this limit, the frequency will not be calculated at all.