Emerson Rosemount Analytical HART 5081-A-HT, Instruction Manual

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10
MODEL 5081-A SECTION 2.0
INSTALLATION
2.4 POWER SUPPLy/CURRENT LOOP
2.4.1 Power Supply and Load Requirements.
Refer to Figure 2-3.
The supply voltage must be at least 12.0 Vdc at the trans-
mitter terminals. The power supply must be able to cover the
voltage drop on the cable as well as the load resistor (250
W
minimum) required for HART communications. The maxi-
mum power supply voltage is 42.0 Vdc. For intrinsically
safe installations, the maximum power supply voltage is
30.0 Vdc. The graph shows load and power supply require-
ments. The upper line is the power supply voltage needed
to provide 12 Vdc at the transmitter terminals for a 22 mA
current. The lower line is the power supply voltage needed
to provide 30 Vdc for a 22 mA current.
The power supply must provide a surge current during the
first 80 milliseconds of startup. The maximum current is
about 24 mA.
For digital communications, the load must be at least 250 ohms. To supply the 12.0 Vdc lift off voltage at the transmitter,
the power supply voltage must be at least 17.5 Vdc.
FIGURE 2-3. Load/Power Supply Requirements
FIGURE 2-4. Power Supply/Current Loop Wiring
2.4.2 Power Supply-Current Loop
Wiring.
Refer to Figure 2-4.
Run the power/signal wiring through
the opening nearest terminals 15
and 16. Use shielded cable and
ground the shield at the power sup-
ply. To ground the transmitter, attach
the shield to the grounding screw on
the inside of the transmitter case. A
third wire can also be used to con-
nect the transmitter case to earth
ground.
NOTE
For optimum EMI/RFI
immunity, the power sup-
ply/output cable should be
shielded and enclosed in an
earth-grounded metal con-
duit.
Do not run power supply/signal
wiring in the same conduit or cable
tray with AC power lines or with
relay actuated signal cables. Keep
power supply/signal wiring at least
6 ft (2 m) away from heavy electrical
equipment.
DWG. NO. REV.
45081A01 A