CiDRA SONARtrac PW VF-100 - Manual (Page 163)

20834-01 Rev 04 Page 8-19
consecutive measurements is less than the measurement range
(default of 100 % for GVF) times (‘Percent’ / 100).
The allowable Reading-to-Reading Variation (RRV) is the device
Maximum Measurable Value (MaxMV) in % GVF minus the device
Minimum Measurable Value (MinMV)
in % GVF times the ‘Delta’ input
by the user to be used for the filter; or:
RRV = [(MaxMV – MinMV) * Delta]
For example, in a device with a GVF MaxMV of 100% GVF and GVF
MinMV of 0% and a ‘Percent’ of 5%, reading variations greater than
5% will be rejected.
RRV = [(100 – 0) * 0.05] = 5%
Therefore, measured points that have measurement variations greater
than 5% will not be displayed or outputted until the number of
consecutive readings that do not vary by more than RV is greater than
that set by ‘Filter Len’.
8.3.8.5 Percent Len
The Percent Len (Filter Percentage Window Length) is used in
conjunction with the ‘Percent’ or ‘Delta’ parameter. After ‘Percent Len’
measurements with good quality have been displayed a new
measurement with good quality is deemed valid and displayed when
the difference between the maximum and minimum of the present
measurement and (‘Percent Len’ - 1) previous consecutive
measurements is less than the measurement range (default of 27fps
for Flow) times (‘Percent’ / 100).
8.3.8.6 Example VF Spike Filter
The following is an example of application of the Spike Filter
8.3.8.6.1 Settings:
No Flow Length = 5
Filter Length = 3
Up Count = 3
Down Count = 2
Percent = 20%
Percent Length = 3
Flow Max = 30 ft/s
Flow Min = 3 ft/s
Measurement Range = (Flow Max
– Flow Min) = 27 ft/s
8.3.8.6.2 No Flow Condition
When the device first powers up it starts in what is called a No Flow
Condition. While in a No Flow Condition the device displays dashes.
This condition is maintained until No Flow Length consecutive good
quality measurements have been made. In this example, the device