Resonant column testing: The inherent counter EMF effect

Yu Hsing Wang*, Giovanni Cascante, J. Carlos Santamarina

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

40 Scopus citations


The standard magnet-coil driving system in resonant column devices provides the required cyclic excitation; however, it inherently produces a counter electromotive force that opposes the motion. In this study, the resonant column is modeled as an electro-mechanical system to quantitatively examine the counter electromotive effect and to explore its effect on resonant frequency and damping ratio computed from voltage-based measurements. The model is verified with two independent sets of experiments. Experimental and analytical results show that the measurement bias is more pronounced on the damping ratio than on the resonant frequency, the damping bias is not a device constant but varies with frequency, and the error is particularly relevant in low-loss and low-stiffness specimens (such as dry sands at low confinement). The electro-mechanical model permits developing device-specific correction charts that can be used to reexamine previously published damping ratio data gathered with voltage-based resonant column procedures.

Original languageEnglish (US)
Pages (from-to)342-352
Number of pages11
JournalGeotechnical Testing Journal
Issue number3
StatePublished - Sep 2003
Externally publishedYes


  • EMF effect
  • Magnet-coil driving system
  • Resonant column testing

ASJC Scopus subject areas

  • Geotechnical Engineering and Engineering Geology


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