Campbell CDM-VW300 Series User Manual Download

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CDM-VW300 Series Dynamic Vibrating-Wire Analyzers

Low-amplitude warning flag

— flag is set true when the resonant amplitude of

the vibrating wire falls to or below 50% of the value entered in

DVWTool

CDM_VW300Config()

. Resonant amplitude must be maintained higher than

50% to ensure an accurate measurement.

High-amplitude warning flag

— flag is set true when the resonant amplitude of

the vibrating wire reaches or exceeds 200% of the value entered in

DVWTool

CDM_VW300Config().

Resonant amplitude must be maintained less than 200%

to ensure an accurate measurement.

Low-frequency warning flag

— flag is set true when the frequency of the

vibrating wire falls between the

Actual Min Freq (Hz)

shown in

DVWTool

and

the

Minimum Frequency (Hz)

entered in

DVWTool

. The

CDM_VW300Config()

instruction equivalent to

Minimum Frequency (Hz)

the

LowFreq

parameter. When a low-frequency limit is entered into

DVWTool

the CRBasic program, an error window is created that spans the bandwidth
between the frequency cut-off requested (

Minimum Frequency

LowFreq

) and

the frequency cut-off the analyzer can actually establish (

Actual Min Freq

). If a

measured frequency falls within the error band, the low-frequency warning flag is
set true.  For example, if a low-frequency limit of 500 Hz is entered, and the
closest the analyzer can come to complying is to set the limit at 476.85 Hz, any
frequency below 476.85 Hz is discarded, and any frequency above 476.85 Hz is
used.  However, any frequency between 476.85 Hz and 500 Hz will activate the
low-frequency warning flag, indicating that the data includes at least one
measurement below the user set limit.  See Section 8.5.1.2,

Calculating Low- and

High-Frequency Boundaries

, for more information.

High-frequency warning flag

— flag is set true when the frequency of the

vibrating wire falls between the

Actual Max Freq (Hz)

shown in

DVWTool

and

the

Maximum Frequency (Hz)

entered in

DVWTool

. The

CDM_VW300Config()

instruction equivalent to

Maximum Frequency (Hz)

the

HighFreq

parameter. When a high-frequency limit is entered into

DVWTool

or the CRBasic program, an error window is created that spans the bandwidth
between the frequency cut-off requested (

Maximum Frequency

HighFreq

)

and the frequency cut-off the analyzer can actually establish (

Actual Max Freq)

If a measured frequency falls within the error band, the high-frequency warning
flag is set true.  For example, if a high-frequency limit of 1000 Hz is entered, and
the closest the analyzer can come to complying is to set the limit at 1049.07 Hz,
any frequency above 1049.07 Hz is discarded, and any frequency below 1049.07
Hz is used.  However, any frequency between 1000 Hz and 1049.07 Hz will
activate the high-frequency warning flag, indicating that the data include at least
one measurement above the user set limit.  See Section 8.5.1.2,

Calculating Low-

and High-Frequency Boundaries

, for more information.

8.5.1.2

Calculating Low- and High-Frequency Boundaries

The easiest way to minimize the size of the low- and high-frequency error
windows is to enter estimated limits into the

Minimum Frequency

and

Maximum Frequency

columns in the

DVWTool

main screen, record the resulting

values displayed in the

Actual Min Freq

and

Actual Max Freq

columns, then

turn around and enter those values back into the

Minimum Frequency

and

Maximum Frequency

columns or the

LowFreq

and

HighFreq

parameters in the

CDM_VW300Config()

CRBasic instruction.

However, to calculate the actual-minimum and actual-maximum frequencies,  use
the information in Table 8-1 to size the value.  For example, to calculate the
actual-minimum frequency, assuming a measurement is to be taken at a scan rate
of 20 Hz, use an integer multiple of 47.68 to calculate the actual-minimum
frequency.  If the low-frequency limit is estimated to be 150 Hz, enter 3 x 47.68,