Aalborg PWE Digital - Manual (Page 51)

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The digital filter only works with pulse width measurement method and is not
applicable for flow measurement mode (a) – “number of pulses over measure
interval”. A typical display with Measure Mode selection is shown below. By
default unit shipped from the factory with Measure Mode set to “Pulse Width”.
4.9.5 Submenu Noise Reduction Filter Damping
Time Numerical entry
A noise reduction filter algorithm (running average of the individual flow inputs) is
available in the flow meter when pulsating flow or especially noisy signals are
encountered. There are two parameters that make up Signal Processing Control:
Damping Time and Number of Samples. They are described individually below.
Damping Time: The damping value can be selected between 0 and 99 seconds.
The value represents the response time of the running average flow rate change.
The higher the damping value the longer the response time of the filter. If noise
reduction filter is not desired it may be disabled by setting Damping Time param-
eter to zero. By default unit shipped from the factory with Damping Time value set
to 5. A typical display with Damping Time selection is shown below.
4.9.6 Submenu Noise Reduction Filter Sample
Number Numerical entry
This is the second parameter that makes up noise reduction filter algorithm. The
sample number value can be selected between 1 and 32. The number of samples
value represents the number of previous individual 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 out-
put reading will be to the actual flow change. A suggested nominal number of 5
samples is a good starting point for most applicable process fluids. A typical dis-
play with Sample Number selection is shown below.
Measure Mode
Pulse Width
NRF Damping Time
05 Seconds