Campbell Scientific AVW200 AVW200-series Vibrating Wire Interfaces - Page 16

AVW200-series 2-Channel Vibrating Wire Spectrum Analyzer Modules Diaphragm Vibrating Wire Plucking/ Pickup Coil FIGURE 2-1. Cutaway of Vibrating Wire Sensor There are three user-determined inputs to the AVW200 measurement process and five outputs from the measurement process. The input parameters control the excitation frequency range (BeginFreq and EndFreq) and the excitation amplitude (ExVolt); see TABLE 2-1. The frequency range supported spans from 100 Hz to 6500 Hz. TABLE 2-1. AVW200 Measurement Inputs Input Units Description BeginFreq Hz Minimum excitation and analysis frequency EndFreq Hz Maximum excitation and analysis frequency ExVolt Unitless Excitation voltage 1: 5 Volts peak to peak 2: 12 Volts peak to peak Therm50_60Hz (see Section 2.2) Unitless Thermistor measurement parameter 0: No thermistor measurement _60Hz Use 60 Hz noise rejection _50Hz: Use 50 Hz noise rejection The measurement outputs are resonant frequency, response amplitude, signalto-noise ratio, noise frequency, and decay ratio; see TABLE 2-2. The raw frequency measurement output of the AVW200 is in Hertz unlike our previous interfaces, which output kHz2 or 1/T2 (where T is the period in milliseconds). The Hertz output is converted to the appropriate units of measurement (e.g., pressure, strain, displacement) by using information provided on the sensor's calibration report. Read more! You can find an example of converting Hertz to displacement in Appendix A and an example program that converts Hertz to displacement in Section 7.1.2. 8