Emerson 8800A, Product Manual

Page: 145 / 160

D-3
Model 268 Communicator
CONNECTIONS
AND HARDWARE The Model 268 can communicate with a transmitter from the control
room, the transmitter site, or any other wiring termination point in the
loop. To communicate, it must be connected in parallel with the
transmitter; the connections are non-polarized.
NOTES
The HART Communicator needs a minimum of 250 ohms resistance in
the loop to function properly. The HART Communicator does not
measure loop current directly.
The Model 268 cannot measure loop current directly.
Figure D-2. Connecting the Model 268 to a Transmitter Loop
Figure D-4. Connecting the Model 268 to a Transmitter Loop
A HART-based communicator may be
connected at any termination point in the
signal loop. Signal loop must have 250
ohms minimum load for communications.
R
L
˜
250
W
Electronic
Totalizer/Counter
–
+
+
+
1K
W
Typical
+
Communicator
Test
Ammeter
(1)Resistor may be internal or external
to Electronic Totalizer/Counter.
dc Volts
Resistor < 0.12 A.
30 V dc
(Max) Out
(1)
+
Power
Supply
Housing Ground
Counter
Input
+
–
–
–
88
00
-0
0
0
0
A
0
3B
A HART-based communicator may
be connected at any termination
point in the signal loop. Signal loop
must have 250 ohms minimum load
for communications.
R
L
˜
250
W
+
+
+
–
–
–
+
+
Test
Ammeter
+
–
Power
Supply
(30 V max)
+
Power
Supply
Housing Ground
Communicator
+
–
–
+
–
88
00-
0
00
0A
0
3
A