Campbell Scientific CDM-VW300 Series Dynamic Vibrating-Wire Analyzer System - Manual (Page 64)

CDM-VW300 Series Dynamic Vibrating-Wire Analyzers
that those readings are correct and can be viewed with RTDAQ or
LoggerNet.
4. If temperature and battery measurements in step 1 are successful,
reconnect the CDM-VW300 to the datalogger and send the 1 Hz program
listed in Appendix G.2, Static Measurements, to the datalogger. If the
temperature and battery measurement are unsuccessful, contact a
Campbell Scientific application engineer.
8.4 Filtering Harmonics
Occasionally, a sensor output can consistently report a harmonic instead of the
fundamental frequency. Most vibrating-wire sensors are designed such that
harmonic frequencies are much less prominent in the signal than the
fundamental. However, especially in worn or damaged sensors, harmonics can
become a significant part of wire motion. A knowledge of the spectral response
of a sensor will help set the maximum and minimum response frequencies
properly. See Section 7.11.1, Frequency Range, and Section 8.5.1.2,
Calculating Low- and High-Frequency Boundaries, for more details. If
adjustment of max and min response settings does not remedy the problem,
force the CDM-VW300 device to re-assess the primary frequency by a)
disabling and re-enabling a channel, or b) re-sending the CRBasic program to
the datalogger.
8.5 Diagnostic Outputs
Diagnostic outputs given by CDM-VW300 series analyzers include:
• Long integer diagnostic codes output at 20, 50, 100, 200 or 333.3 Hz
for each enabled channel.
• Standard deviation calculated from the dynamic readings output at 1
Hz for each enabled channel.
8.5.1 Diagnostic Codes (Dynamic)
Diagnostic codes are returned with each dynamic frequency measurement
made by the CDM-VW300 analyzer. Each diagnostic code is a 32-bit
unsigned integer encoded with five diagnostic parameters. This method of
reporting diagnostics minimizes data sent over the CPI bus, which helps to
maximize measurement throughput rates. The five diagnostic parameters are:
1. Excitation strength
2. Low-amplitude warning flag
3. High-amplitude warning flag
4. Low-frequency warning flag
5. High-frequency warning flag
Each parameter is explained fully in Section 8.5.1.1, Description of Diagnostic
Parameters. The third argument of the CDM_VW300Dynamic() instruction
specifies the variable array to which the 32-bit diagnostic codes are written.
This array is dimensioned up to a number equal to the maximum number of
channels of the analyzer. For example, when the CDM-VW305 is measuring
eight channels at 100 Hz, the diagnostic code array should be dimensioned to
(8). Each variable in the array receives 100 diagnostic codes per second, or
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