FFT Settings

FFT Points and Number Points are tightly coupled, so changes to one should be followed by changes to other.

Default Settings

Note: By Default, changing FFT Points will increase the # Points to Record proportionally for ease of use.

Effects of increasing FFT Points:

Pros	Cons
Measure lower frequencies Lowest Measureable Frequency = 8000(or Nyquist Freq) / FFT Points Finer FFT Resolution	More FFT points = more processing time during autotuning If Number Points is not increased, data may become noisier

Effects of Increasing Number of Points

Pros	Cons
Smoother Data, more raw data points averaged per FFT data point	More time will be spent during the excitation portion of bode measurements to collect the data

Examples will be shown in the Manual Tuning Section.

Review:

FFT Points and Number Points are tightly coupled, when one is modified, the other should be too.

To get better low frequency data, increase FFT Points to 32768, this will generate a frequency measurement at 0.25Hz. Also increase Number of Points to 240000 – if this is not increased, the measurement will likely be noisy.

Default settings are good for most systems. As loads get more complex, manual tweaking may be required to obtain a quality measurement.