Campbell Scientific CDM-VW300 Series Dynamic Vibrating-Wire Analyzer System - Manual (Page 46)

CDM-VW300 Series Dynamic Vibrating-Wire Analyzers
7.5.11 Channels Enabled
Each channel on a CDM-VW300 series analyzer can be individually enabled
for measurement. If a channel is not enabled, the LED corresponding to it will
not flash. If the channel is enabled, but there is a diagnostic warning, the LED
will flash red. If the device is enabled and obtaining a reading properly from
the attached sensor, the LED will flash green. Channels are enabled either with
check boxes or Boolean values.
7.5.12 Desired Resonant Amplitude
This is the target amplitude, measured in volts, for keeping the wire of the
sensor in constant excitation. The excitation voltage is adjusted automatically
by the analyzer to accommodate the target resonant amplitude. This is set to a
minimum of 100 µV and a maximum of 10 mV. Default is 2 mV.
7.5.13 Minimum- and Maximum Cut-Off Frequencies
Band-pass filters can be set to isolate a certain frequency range within which a
reading is expected to fall. See Section 7.11.1, Frequency Range, for more
information. Settings are frequency values.
7.5.14 Frequency-Output Format
Use this setting to select whether the output from the sensor will be given as
frequency (Hz) or frequency squared (Hz
2 ). Settings are selected from lists in
the PC software. Entry in CRBasic is Boolean (0 = Hz, 1 = Hz 2 ).
7.5.15 Multipliers and Offsets
Multipliers (gain, slope, or scaling) and offsets (y-intercept or shifting) allow
for linear scaling of the frequency output of each sensor. Some vibrating-wire
sensors, however, require polynomial calculations to obtain the desired
engineering units. If transformation other than linear scaling is required, the
multiplier should be set to 1 and the offset to 0, and the transformation made
through other datalogger calculations or by post-processing of the data. Please
refer to the calibration sheet that came with each sensor to understand how the
frequency output should be transformed to obtain the desired engineering units.
Appendix D, Digits Conversion, and Appendix E, Calculating Measurement
Error, contain additional information about conversion from frequency to
engineering units.
7.5.16 Steinhart-Hart Coefficients
These coefficients are used to convert thermistor resistance from ohms to
temperature in degrees Celsius. See Appendix F, Thermistor Information, for
more information.
7.5.17 Rainflow-Histogram Output Configurations
Output configuration settings in DevConfig and CRBasic are three digit values.
For example, an entry of 100 means reset histogram, divide bins by total count,
and use open form.
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