Campbell Scientific CDM-VW300 Series Dynamic Vibrating-Wire Analyzer System - Manual (Page 47)

CDM-VW300 Series Dynamic Vibrating-Wire Analyzers
Options:
• 0 = reset histogram each output / 1 = Do not reset histogram.
• 0 = Divide bins by total count / 1 = use the total of each bin.
• 0 = Open form (includes half cycles) / 1 = Closed form (use full
cycles)
Settings in DVWTool are selected from lists.
7.6 Sensor Selection
CDM-VW300 series analyzers work well with standard vibrating-wire sensors
that use a single-coil circuit design. In this design, two sensor leads are used to
both excite the sensor and read back the resonant frequency. When selecting a
vibrating-wire sensor, consider its frequency range and the sample rate at
which that frequency will be sampled by the datalogger or PC.
7.6.1 Frequency Considerations
In general, sensors with higher resonant-frequency ranges are more versatile
when used with a CDM-VW300 series analyzer. Higher sample rates require a
higher-frequency range on the sensor.
Based on the dynamic rate used to sample the sensor, be aware of the low-end
(minimum) frequency limitations of the CDM-VW300 as given in the
following table:
TABLE 7-2. Relationship of Sample Rate and Sensor Frequency
Sample
Rate (Hz)
Min Sensor
Freq (Hz)
Max Sensor
Freq (Hz)
20 290 6000
50 290 6000
100 580 6000
200 1150 6000
333.3 2300 6000
Be sure that the expected frequency response of the sensor does not fall outside
the specified limits even when responding to maximum or minimum
measurement conditions.
7.6.2 Noise Performance
See Section 5.2, Specifications, for more information about the noise and
accuracy of frequency readings at various sampling rates.
7.7 System Connections
IMPORTANT — Do not connect the CDM-VW300 analyzer or SC-CPI
interface to a PC until AFTER installing DVWTool 1.0 or later or DevConfig
2.04 or later. Consult Section 7.1.1, Software and Driver Installation, for more
information.
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