Operational Modal Testing

EDM Modal Operational Modal Testing (OMA Testing) includes a dedicated test setup and operation process flow using ambient vibration data. Using a large channel count data acquisition system (e.g., Spider- 80X or Spider-80Xi), the excitation method provides a much higher efficiency and accuracy for FRF measurements while minimizing local stresses on the test article.

Typical modal analysis methods and procedures are based on forced excitation tests carried out in the laboratory. Frequency Response Functions (FRFs) are measured as input to modal parameter identification. However, the real loading conditions to which a structure is subjected often differs considerably from those used in a laboratory testing. In many cases, (i.e., excitation of off-shore platforms or traffic/wind excitation of a bridge,) forced excitation tests are very difficult, if not impossible to conduct; at least when using standard testing equipment. In such cases, operational vibration data is often the only resource available.

Operational modal testing is designed to measure and process ambient vibration response data, which will be ready for parameter identification. The resulting cross power spectrum vector(s) can be further smoothed by using the de-convolution method.


The modal analysis process is seamlessly integrated with Operational Modal testing.


  • Ease of use testing process
  • Point/direction auto/manual increment
  • User defined reference channel
  • Scope tab to view channel data before measurement
  • Expanded cross power spectrum for all input channel vs. reference channel
  • Cross power spectrum vector(S) smoothing, multiple times or cancel