Campbell Scientific CR6 CR6 Measurement and Control System - Page 351

Figure 97. Unconditioned Vspect Data Section 8. Operation Vspect Diagnostics The following data are diagnostic for the condition of a vibrating-wire sensor: • Decay ratio • Signal-to-noise ratio • Low signal-strength amplitude warning • Invalid voltage-supply warning The time-series data graphed in the figure Unconditioned Time-Series Data (p. 350) show the decay from the start of the sampling, labeled Beginning Amplitude, to the end of the sampling, labeled Ending Amplitude. "Decay" is the dampening of the wire over time. The decay ratio is calculated as follows: Decay Ratio = Ending Amplitude / Beginning Amplitude Some sensors will decay very rapidly. A good practice is to characterize sensor decay and amplitude when a sensor is new, so the condition of the sensor can be monitored over time. The spectrum data shown in the figure Unconditioned Spectrum-Analysis Data (p. 351) are derived from the time-domain data through an FFT (p. 495). These data emphasize the amplitude of the natural-resonant frequency, labeled Response Amplitude, and the amplitude of noise frequencies, labeled Noise Amplitude. The signal-to-noise ratio is calculated as follows: Signal-to-Noise Ratio = Response Amplitude / Noise Amplitude Decay Ratio Diagnostic The time-series data graphed in the figure Unconditioned Time-Domain Data (p. 350) show the decay from the start of the sampling, labeled Beginning Amplitude, to the end of the sampling, labeled Ending Amplitude. "Decay" is the dampening of the wire over time. The decay ratio is calculated as follows: Decay Ratio = Ending Amplitude / Beginning Amplitude Some sensors will decay very rapidly. A good practice is to characterize sensor decay and amplitude when a sensor is new, so the health of the sensor can be monitored over time. 351