dynasonics TFXL series - Filtering Tab

Filtering Tab
The Filtering tab contains several filter settings for the transmitter. These filters can be adjusted to match response times and
data “smoothing” performance to a particular application.
Figure 34: Filtering tab
Parameter Meaning Option Description
Time Domain
Filter
Number of
raw data sets
averaged
together
1…256
Time Domain Filter (range 1…256) adjusts the number of raw data sets (the wave forms viewed
on the software Diagnostics Screen) that are averaged together. Increasing this value will provide
greater damping of the data and slow the response time of the transmitter. Conversely, lowering
this value will decrease the response time of the transmitter to changes in flow/energy rate. This
filter is not adaptive, it is operational to the value set at all times.
OTE:N The transmitter completes a measurement in approximately 350…400 mS. The exact
time is pipe size dependent.
Flow Filter
(Damping)
Maximum
adaptive filter
value
(Enter a numeric
value)
Flow Filter (Damping) establishes a maximum adaptive filter value. Under stable flow conditions
(flow that varies less than the Flow Filter Hysteresis entry), this adaptive filter will increase the
number of successive flow readings that are averaged together up to this maximum value. If
flow changes outside of the flow filter hysteresis window, the filter adapts by decreasing the
number of averaged readings and allows the transmitter to react faster.
The damping value is increased to increase stability of the flow rate readings. Damping values
are decreased to allow the transmitter to react faster to changing flow rates. The factory settings
are suitable for most installations. Increasing this value tends to provide smoother steady-state
flow readings and outputs.
Flow Filter
Hysteresis
Allows variations
in flow
(Enter a numeric
value)
Flow Filter Hysteresis creates a window around the average flow measurement reading allowing
small variations in flow without changing the damping value. If the flow varies within that
hysteresis window, greater display damping will occur up to the maximum values set by the flow
filter entry. The filter also establishes a flow rate window where measurements outside of the
window are examined by the Bad Data Rejection filter. The value is entered as a percentage of
actual flow rate.
For example, if the average flow rate is 100 gpm and the Flow Filter Hysteresis is set to 5%, a
filter window of 95…105 gpm is established. Successive flow measurements that are measured
within that window are recorded and averaged in accordance with the Flow Filter Damping
setting. Flow readings outside of the window are held up in accordance with the Bad Data
Rejection filter.
Flow Filter
MinHysteresis
Minimum
hysteresis window
(Enter a numeric
value)
Flow Filter MinHysteresis sets a minimum hysteresis window that is invoked at sub 0.25 fps (0.08
mps) flow rates, where the “of rate” flow filter hysteresis is very small and ineffective. This value
is entered in pico-seconds (ρsec) and is differential time. If very small fluid velocities are to be
measured, increasing the flow filter minhysteresis value can increase reading stability.
Flow Filter
Sensitivity
Sets damping
speed
(Enter a numeric
value)
Flow Filter Sensitivity allows configuration of how fast the Flow Filter Damping will adapt in the
positive direction. Increasing this value allows greater damping to occur faster than lower
values. Adaptation in the negative direction is not user adjustable.
Bad Data
Rejection
Sets the number
of readings to
measure
(Enter a numeric
value)
Bad Data Rejection is a value related to the number of successive readings that must be
measured outside of the Flow Filter Hysteresis or Flow Filter MinHysteresis windows before the
transmitter will use that flow value. Larger values are entered into Bad Data Rejection when
measuring liquids that contain gas bubbles, as the gas bubbles tend to disturb the ultrasonic
signals and cause more extraneous flow readings to occur. Larger Bad Data Rejection values tend
to make the transmitter more sluggish to rapid changes in actual flow rate.
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Page 36 April 2016TTM-UM-00369-EN-03