Measurement Principle

The key components of a standard single-coil vibrating wire (VW) sensor are the following:

• A taut wire suspended between two anchor points
• An electromagnetic coil positioned at the center of the wire

The coil serves two functions:

1. As an actuator to put energy into the wire
2. As a pickup to detect the motion of the wire

Static VW measurements are typically performed in a two-step process of exciting the wire and then measuring the wire response for a period to determine its resonant frequency. The excitation waveform must be spectrally broad, such as a swept-frequency sine wave, so as to provide sufficient energy at the unknown resonant frequency of the wire. After the excitation, the resonant motion of the wire is sampled, the frequency is determined, and then the resonant energy dissipates prior to making the next measurement. The time required for these steps typically limits this approach to measurement rates slower than 1 Hz.