AVW200
2-Channel Vibrating-Wire Spectrum Analyzer
The AVW200 interface module applies a new method for measuring a sensor's frequency. The AVW200 eliminates the problem of incorrect readings due to noise sources. The noise problems are overcome by an advancement in technology and mathematical processing, resulting in frequency-based measurements—a complete departure from previous time-domain-based measurements.
In the traditional time-domain approach, the natural or resonant frequency at which the wire is oscillating is determined by exciting the wire with an AC excitation, stopping the excitation, and then measuring time between response pulses.
In addition to refining the AC excitation, the new method featured in the AVW200 takes advantage of its built-in spectrum analyzer that uses spectral interpolation instead of the traditional pulse-timing approach. It samples the returned signal, performs an FFT (fast Fourier transform) to discriminate between spectral components, and then identifies and measures the resonant frequency of the sensor. This means that even in noisy environments the sensor’s resonant frequency can be identified and accurately measured.
The new method also provides much better measurement resolution (improving from 0.01 Hz to 0.001 Hz) as well as diagnostic information about the measured frequency. This diagnostic information includes the signal-to-noise ratio, amplitude of the dominant frequency, and an optional spectrum showing all of the frequency components.
The AVW200 can be used via SDI-12, RS-232, or PakBus network protocol. Its low power consumption and rugged design match the durability and long-term stability of vibrating-wire sensors. Wireless versions are also available, allowing for remote deployment separate from the datalogger.
