Campbell Scientific AVW200-series Vibrating Wire Interfaces - Manual (Page 15)

AVW200-series 2-Channel Vibrating Wire Spectrum Analyzer Modules
FIGURE 1-3. Network of AVW200 Interfaces (SDI-12)
2. Measurements
2.1 Vibrating Wire
The spectral approach implemented by the AVW200 offers significantly
improved noise immunity when compared to older period-averaging techniques
implemented by other vibrating-wire interfaces (AVW1, AVW4, and
AVW100). Testing revealed more than two to three orders of magnitude better
noise immunity with the AVW200. In addition, the spectral analysis gives
improved frequency resolution (0.001 Hz rms) during quiet conditions.
The AVW200 measures the resonant frequency of the taut wire in a vibrating
wire sensor (see FIGURE 2-1) with the following procedure. First, the
AVW200 excites the wire with a swept-frequency excitation signal. Next, the
AVW200 records the response from the vibrating wire. Finally, the AVW200
Fourier transforms the recorded response and analyzes the resulting spectrum
to determine the wire’s resonant frequency. This analysis also provides
diagnostic information indicating the quality of the resonant-frequency
measurement.
CR10X
CR5000
CR23X
CR800, CR850
CR1000
CR3000
AVW200
SDI-12
AM16/32B
Datalogger MUST Control
Multiplexers in SDI-12 Mode
0
1
2
3
7