Dynasonics TFXM Series Ultrasonic Multi-Channel Flow Meter - Manual (Page 53)

Rev. 8/02
-3. 15- TFXM
Integral 4-20mA Output
FL 4MA
FL 20MA
CAL 4MA
CAL 20MA
4-20 TST
The 4-20 mA Output interfaces with virtually all recording and
logging systems by transmitting an analog current signal that is
proportional to system flow rate. The output can be configured
to be either internally or externally powered by setting the left
DIP-switch at SW1 for Channel 1 and SW2 for Channel 2. Re-
fer to the Field Wiring Diagram at Figure 1.4 for terminal block
and DIP -switch locations.
When powered from internal power, the 4-20 mA output can
provide loop current for a maximum of 800 ohms of total loop
resistance. When powered externally, the maximum load varies
with the level of the voltage source. The insertion loss of the 4-
20 mA circuit is 5Vdc, so the maximum loop load that can be
powered is calculated by the equation:
Max Loop Load = (External Supply Voltage - 5)
0.02
The FL 4MA and FL 20MA entries are used to set the span of
the 4-20 mA analog output. These entries are volumetric rate
units that are equal to the volumetric units configured as Engi-
neering Rate Units and Engineering Units Time Interval entered
on page 3.10. These entries may be entered anywhere in the
flow measurement range of the instrument (velocity range of –
40 to +40 FPS [-12 to +12 MPS]).
For example, to span the 4-20mA output from –100 GPM to
+100 GPM, with 12mA being 0 GPM, set the FL 4MA and FL
20MA inputs as follows:
FL 4MA = -100.0
PART 3 - KEYPAD CONFIGURATION
2&3. OUTPUT 1 and 2 MENUS
Standard
4-20mA
4-20mA Span