Curve Fitting Guidelines

1. Overlay the Measurements

A resonance peak should appear at the same frequency in every FRF, except where node points (zero residues) of the mode shape occur.

2. Inspect the Impulse Response Functions (IRFs)

Wrap around error (shown below) is not harmful to frequency domain curve fitting.

Impulse Response Functions.

3. Use the Mode Indicator

4. Use Quick Fit First

5. Use the Band cursor

If the Band cursor is displayed, only data in the cursor band is used for curve fitting.
Otherwise, all of the data in each M# is used for curve fitting.

6 Verify Fundamental Mode Shapes

Low frequency modes have simple bending and torsional mode shapes.
Points that animate substantially different from neighboring Points on the structure model are indications of poor measurements, poor curve fits, or both.

7. Compare Results from Different Curve Fitting Methods