Dynasonics TFX Ultra Transit Time Flow Meters - Manual (Page 46)

Low Flow Cut-off
FL C-OFF — Low Flow Cut-off (Value)
0…100%
A low flow cut-off entry is provided to allow very low flow rates (that can be present when pumps are off and valves are
closed) to be displayed as zero flow. Typical values that should be entered are between 1.0% and 5.0% of the flow range
between MIN RATE and MAX RATE.
Damping Percentage
DAMP PER — System Damping (Value)
0…100%
Flow filter damping establishes a maximum adaptive filter value. Under stable flow conditions (flow varies less than 10%
of reading), 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 10% window, the flow filter adapts by decreasing the number of averaged
readings which allows the meter to react faster. Increasing this value tends to provide smoother steady-state flow readings
and outputs. If very erratic flow conditions are present or expected, other filters are available for use in the software utility. See
SOFTWARE UTILITY of this manual for further information.
CH1 Menu — Channel 1 Menu
CH1 MENU — 4-20 mA Output Menu
4-20 MA — 4-20 mA Setup Options (Values)
FL 4MA Flow at 4 mA
FL 20MA Flow at 20 mA
CAL 4MA 4 mA Calibration
CAL 20MA 20 mA Calibration
4-20 TST 4-20 mA Test
The CH1 menu controls how the 4-20 mA output is spanned for all flow meter models and how the frequency output is
spanned for the flow only model.
The FL 4MA and FL 20MA settings are used to set the span for both the 4-20 mA output and the 0…1000 Hz frequency output
on the flow only meter versions.
The 4-20 mA output is internally powered (current sourcing) and can span negative to positive flow/energy rates. This output
interfaces with virtually all recording and logging systems by transmitting an analog current that is proportional to system
flow rate. Independent 4 mA and 20 mA span settings are established in firmware using the flow measuring range entries.
These entries can be set anywhere in the –40…40 fps (–12…12 mps) range of the instrument. Resolution of the output is
12-bits (4096 discrete points) and the can drive up to a 400 Ohm load when the meter is AC powered. When powered by a DC
supply, the load is limited by the input voltage supplied to the instrument. See Figure 23 for allowable loop loads.
FL 4MA — Flow at 4 mA
FL 20MA — Flow at 20 mA
The FL 4MA and FL 20MA entries are used to set the span of the 4-20 mA analog output and the frequency output on flow only
versions. These entries are volumetric rate units that are equal to the volumetric units configured as RATE UNT and RATE INT
discussed previousley.
For example, to span the 4-20 mA output from –100…100 gpm, with 12 mA being 0 gpm, set the FL 4MA and FL 20MA inputs
as follows:
FL 4MA = –100.0
FL 20MA = 100.0
If the meter were a flow only model, this setting would also set the span for the frequency output. At –100 gpm, the output
frequency would be 0 Hz. At the maximum flow of 100 gpm, the output frequency would be 1000 Hz, and in this instance a
flow of zero would be represented by an output frequency of 500 Hz.
BSC MENU – BASIC MENU
Page 46 March 2014