CiDRA SONARtrac PW VF-100 - Manual (Page 104)

20833-01 Rev 04 Page 7-10
7.3.4 CUR1 (Primary 4-20mA Output)
These terminals are used for connection to the primary 4-20mA output
from the transmitter. The transmitter can be configured such that an
external supply can be used for power (i.e. the 4-20mA loop current is
driven externally) or such that the transmitter itself will power the loop
(internal power). A combination of power wiring and internal software
settings will ensure that the 4-20mA output will function properly. The
following figures show proper wiring for internal and external power.
The software configuration must be set to match the external wire
connections for proper operation of this output. The primary 4-20mA
output is the only 4-20mA output that supports HART communication.
7.3.5 CUR2 (Secondary 4-20mA Output)
These terminals are used for connection to the secondary 4-20mA
output from the transmitter. As with the primary 4-20mA line, the
transmitter can be configured such that an external supply can be
used for power or such that the transmitter itself will power the loop. A
combination of power wiring and internal software settings will ensure
the 4-20mA output will function properly. The software configuration
must be set to match the external wire connections for proper
operation of this output.
7.3.5.1 Internally Powered 4-20mA Loop Configuration
The connections for a 4- 20mA interface configured as “Internally
Powered” are shown below. The maximum value of R
L
is 500 Ohms.
The voltage across R
L
must be measured differentially. The V
-
INT
connection is tied to a
–10V reference internal to the transmitter and
must not be connected to ground in the plant control system.
Figure 9 Internally (Transmitter) Powered 4 –20mA Loop
-
+
(-10v)
R
L
Plant control system
Measure
differentially
Do Not Tie
R
L
To GND
Transmitter
4-20mA
driver
+
+12v
-
+
+10v
-