Emerson Rosemount 3144P, Справочное руководство

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20
Reference Manual
00809-0100-4021, Rev JA
Installation
April 2017
Installation
2.5.6 Multichannel installation (HART/4–20 mA only)
Several transmitters can be connected to a single master power supply (see figure below). In this case,
the system may be grounded only at the negative power supply terminal. In multichannel installations,
where several transmitters depend on one power supply and the loss of all transmitters would cause
operational problems, consider an uninterrupted power supply or a back-up battery. The diodes shown
in
Figure 2-10 prevent unwanted charging or discharging of the back-up battery.
Figure 2-10. Multichannel Installations
A.Transmitter no. 1
B. Transmitter no. 2
C. R
Lead
D. Readout or controller no. 1
E. Readout or controller no. 2
F. Battery Backup
G. dc Power supply
2.6 Wiring
2.6.1 HART/4–20 mA
Field wiring
The power to the transmitter is supplied over the signal wiring. Signal wiring does not need to be
shielded, but twisted pairs should be used for best results. Do not run unshielded signal wiring in conduit
or open trays with power wiring or near heavy electrical equipment because high voltage may be present
on the leads and may cause an electrical shock. To wire the transmitter for power:
1. Remove the transmitter covers. Do not remove the transmitter covers in an explosive atmosphere
when the circuit is live.
2. Connect the positive power lead to the terminal marked “+” and the negative power lead to the
terminal marked “–” as shown in Figure 2-11 . Crimped lugs are recommended when wiring to screw
terminals.
3. Tighten the terminal screws to ensure good contact is made. No additional power wiring is required.
4. Replace the transmitter covers making sure both transmitter covers are fully engaged to meet
explosion-proof requirements.
A
B
C
D
E
F
G
H
Between 250 and 1100
Ω
If
no load resistor
Between 250 and 1100
Ω
If
no load resistor