CiDRA SONARtrac PW VF-100 - Manual (Page 162)

20834-01 Rev 04 Page 8-18
counter becomes less than or equal to zero then the current
measurement is displayed. If the quality counter becomes greater
than or equa
l to (‘Filter Length’ x ’Up Count’) then the device is forced
into a ‘No Flow’ condition and displays dashes.
8.3.8.2 Down Count
This parameter is used in conjunction with the ‘Up Count’ parameter
and is used when the device is ‘Holding’ a previous measurement due
to a new measurement with bad quality. Each time a measurement
with bad quality is made ‘Up Count’ is added to an entity called the
quality counter and each time a measurement with good quality is
made ‘Down Count’ is subtracted from the quality counter. If the
quality counter becomes less than or equal to zero then the present
measurement is displayed. If the quality counter becomes greater
than or equal to (‘Filter Length’ x ’Up Count’) then the device is forced
into a ‘No Flow’ condition and displays dashes.
8.3.8.3 Percent (VF only)
This parameter is used in conjunction with the ‘Percent Len’
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).
The allowable Reading-to-Reading Variation (RRV) is the device
Maximum Measurable Value (MaxMV) in ft/sec minus the device
Minimum Measurable Value (MinMV) in ft/sec times the ‘Percent’
(‘Delta’ for GVF) input by the user to be used for the filter; or:
RRV = [(MaxMV – MinMV) * Percent]
For example, in a device with a velocity MaxMV of 30 fps and velocity
MinMV of 3 fps and a ‘Percent’ of 10%, reading variations greater than
2.7 fps will be rejected.
RRV = [(30 – 3) * 0.10] = 2.7 fps
Therefore, measured points that have measurement variations greater
than 2.7 fps 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’.
8.3.8.4 Delta (GVF only)
This parameter is used in conjunction with the ‘Percent Len’
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