Filter Page
Figure 68: Filter settings
Filter Method
The DXN flow meter offers several levels of signal filtering:
• None
imposes no filtering on the signal from the transducers .
• Simple with Rejection
uses
Damping
and
Bad Data Rejection
to filter the flow data .
• Adaptive
filtering allows the meter’s software routines to alter the filtering, depending on the variability of the transducer’s
signal . The
Adaptive
filter uses a combination of
Damping
,
Bad Data Rejection
,
Sensitivity
and
Hysteresis
to modify the flow
input data .
Damping (Range 0…100 Seconds)
Damping
is the approximate amount of time the filtering routines use to attain a 99% stable rate value . Generally, the higher
the damping value, the more stable the rate readings are—but at the expense of response time .
Sensitivity (Range 0…100%)
Sensitivity
determines how fast the adaptive filtering responds to a change in rate . Increasing the sensitivity decreases the
filtering, which allows the display to respond to rate changes more rapidly .
Hysteresis (Range 0…25%)
Hysteresis
creates a window around the average flow measurement reading, defining the limits at which the automatic
damping increases occur . If the rate varies within the hysteresis window, greater damping occurs up to the maximum values
set by the flow filter
Damping
entry . The filter also establishes a flow rate window where measurements outside of the
window are captured by the
Bad Data Rejection
window . Enter the value as a percentage of actual flow rate .
For instance, a
Hysteresis
setting of 5% allows the flow to vary ± 5% from the currently established flow rate without
automatically decreasing the value of the
Damping
.
For example, if the average flow rate is 100 gpm and the
Hysteresis
is set to 10%, a filter window of 90…110 gpm is
established . Successive flow measurements that reside within that window are recorded and averaged in accordance with the
Damping
setting . Flow readings outside of the window are rejected or accepted in accordance with the
Bad Data Rejection
setting .
Filter settings for this example:
Filter Method
Adaptive
Damping
40 seconds
Sensitivity
60%
Hysteresis
10%
Bad Data Rejection
3
Meter Group
Page 54
November 2016
HYB-UM-00090-EN-04