A vibrating-wire sensor couples an external physical parameter, for example strain or displacement, to the tension of a taut wire within the gage. Because the tension in the wire is related to the wire’s fundamental resonant frequency, measuring the resonant frequency of the wire measures the external physical parameter:
The taut wire in a vibrating-wire sensor is similar to a guitar string. By increasing the tension in the wire (or guitar string), the wire’s resonant frequency increases. While energy is coupled to a guitar string by plucking it, energy is coupled to the wire in a vibrating-wire sensor with a frequency-swept magnetic field that is included in the sensor, as shown in Fig. 3.
Once the wire is vibrating, data-acquisition equipment determines the resonant frequency of the wire and converts this resonant frequency into the desired engineering units.