Aalborg Vortex Insertion - Manual (Page 46)

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The Flow Damping value can be selected between 0 and 99 seconds. The value
represents the response time for a 0 - 66 % step flow rate change. When damp-
ing value set to 0 it is disabled.
A Noise Reduction Filter algorithm (running average of the individual flow
inputs) is available in the flow meter when pulsating flow or especially noisy sig-
nals are encountered.
There are three parameters that make up Signal Processing Control:
- Number of Samples
- Time Limit
- Error Limit
They are described individually below.
Number of Samples [NRF]: The sample number value can be selected between 1
and 32. The number of samples value represents the number of previous individ-
ual inputs used to calculate the average value. Eventually the number of samples
in the running average also affects the response time. The more samples is used,
the more inertial flow output reading will be to the actual flow change. A suggest-
ed nominal number of 16 samples is a good starting point for most applicable
process fluids.
Time Limit: can be selected between 0 and 99 seconds. The value represents the
response time of the running average flow rate change. The higher the Time Limit
the longer the response time of the filter. If noise reduction filter is not desired it
may be disabled by setting Time Limit parameter to zero. By default unit shipped
from the factory with Time Limit value set to 6.
Error Limit: can be selected between 0.0 and 100.0 % of full scale. The value rep-
resents the difference of the signal sample from previous measured value. Error
Limit is configured to reject noise spikes within the flow range while allowing nor-
mal frequency variation of the vortex signal. The factory setting 2.0% of full scale
optimizes noise rejection in most applications.
The Turbulence Flow Window parameter is used to define turbulence conditions.
The value represents the difference between two consecutive measurements in %
of full scale. If the difference between two consecutive measurements will be high-
er than value set for Turbulence Flow Window parameter, the Turbulence Event
will be triggered. Default settings are 30.
NOTE: NRF settings only applicable to PWM algorithm.
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