41
Reference Manual
00809-0400-4101, Rev BA
Electrical Installations
January 2018
Electrical Installations
Figure 4-5. Load Limitation
The total resistance load is the sum of the resistance of the signal leads and the load resistance of the
controller, indicator, I.S. Barriers, and related pieces. If intrinsic safety barriers are used, the resistance
and voltage drop must be included.
4.6.3 Wiring the transmitter
Note
Use shielded twisted pairs to yield best results. To ensure proper communication, use 24 AWG or larger
wire and do not exceed 5000 ft. (1500 m).
Figure 4-6. 4–20 mA HART
A. DC power supply
B. R
L
≥ 250 (necessary for HART communication only)
Perform the following procedure to make wiring connections:
1. Remove the housing cover on terminal compartment side. Do not remove the cover in explosive
atmospheres when the circuit is live. Signal wiring supplies all power to the transmitter.
Maximum loop resistance = 43.5 ⫻ (Power supply voltage – 10.5)
The Field Communicator requires a minimum loop resistance of 250
Ω
for communication.
Do not connect the power signal wiring to the test terminals. Incorrect wiring can damage test circuit.
V
Load (Ωs)
Operating
Region
1387
1000
500
0
10.5 20 30
42.4
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