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9.7.1 Amplitude warning flags
An accurate measurement requires the resonant amplitude of the sensor to be greater than 50 %
and less than 200 % of the Resonant Amplitude setting. If the resonant amplitude is less than 50
% of the resonant amplitude setting, a low-amplitude warning flag is triggered. Greater than 200
% triggers a high-amplitude warning flag. Most sensors respond well to the default amplitude
setting. Weak sensors will require a stronger excitation pulse to achieve the amplitude setting
target value. Raising the amplitude setting gives a larger signal-to-noise ratio but subjects the
sensor to stronger excitation energy.
When the frequency of a sensor changes fast, the measured phenomenon is probably changing
fast. When this happens, energy in the vibrating wire may drop briefly until the excitation
mechanism can insert energy at the new frequency. A low-amplitude warning flag may occur
briefly; this is usually OK.
If a warning flag is present for a long time, check the source of the error as follows:
l
Check the sensor connection.
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Check that the sensor is outputting correct data.
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Fine tune the VWIRE 305 scan rate. See Sample Rate in
l
Check that the frequency being output by the sensor is within one of the frequency output
ranges supported by the VWIRE 305. See the first and third columns in
9.7.2 Diagnostic codes
The VWIRE 305 outputs binary diagnostic codes with each measurement at the VWIRE 305
sample rate. These codes include information about excitation strength, frequency warning flags,
and amplitude warning flags.
When using a data logger with the VWIRE 305, write program code to interpret the diagnostic
codes. An alternative is to save diagnostic codes with the measurement data and interpret the
codes with post processing.
Each diagnostic code is a 32 bit unsigned integer encoded with the following diagnostic
parameters.
l
Excitation strength
l
Low-amplitude warning flag
l
High-amplitude warning flag
l
Low-frequency warning flag
l
High-frequency warning flag
When there are no warning flags, the diagnostic code is between 0 and 255 and indicates only
excitation strength. When there are warning flags the diagnostic code is greater than 255 and is
VWIRE 305
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