Origin of frequency difference between damped and sustained modes in vibrating wire sensors

• Vibrating wire sensors resonant frequency differs according operating mode.
• Average magnetic force and coil–coil coupling are responsible for this difference.
• Effects are calculated and modeled yielding equivalent circuits.
• Measurements allow to validate models and theoretical analysis.
• Correction procedure allows to shift from continuous to damped mode operation.

Vibrating wire sensors can operate in two modes, damped mode and sustained mode. In practice, the resonant frequency measured in sustained mode is higher than the one measured in damped mode. In this paper, the theoretical analysis indicates that average magnetic force and coil coupling are responsible for the frequency difference. This prediction is experimentally confirmed by measuring the resonant frequencies for different values of the two parameters. It is shown how to correct measurements in order to obtain the same results for the two modes.