Eliminating the Resonance Frequency with the Anti-Oscillation Unit

Every force transducer has a resonance frequency at which it vibrates. The SI-AOSUB allows you to locate that frequency and filter the signal to mitigate the noise of the resonance frequency. Since each force transducer is unique, the anti-oscillation unit must be calibrated for each force transducer. Likewise, the tissue mounting hardware affects the resonance frequency. Therefore, the system must be calibrated with the mounting hardware attached to the force transducer.

The SI-AOSUB Anti Oscillation module operates in conjunction with the SI-BAM21-LCB module and the motor controller to actively cancel the force transducer’s natural harmonic resonance. This is critical when performing dynamic muscle contraction and release studies to ensure the integrity of the force signal from the tissue.


  • Adjustable amplitude and frequency of pulse generation to ping transducer resonant frequency
  • LED amplitude meter peaks when resonant frequency is generated

NOTE: When the SI-HTB or SI-MT electronics are configured at the factory for the muscle Tester systems, the signal is routed internally from the SI-BAM21-LCB module to the SI-AOSUB module.

Scope trace for antioscillation

The upper trace is a force transient obtained directly from the bridge amplifier output, and the lower trace shows the signal after it passes through the “anti-oscillation” unit.

The anti-oscillation filter is adjusted at the factory using the force transducer that is supplied with the SI-H Muscle Tester system. Normally, the filter does not need to be reset, unless a different force transducer is connected to the unit. To adjust the anti-oscillation filter properly, the transducer is excited at its resonance frequency using a magnetic driver or pulser (WPI #97204).

The Pinger

The Pinger (WPI #97204) is included with the anti-oscillation module.

See Selection