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Reference Manual
00809-0100-4021, Rev DA
November 2004
Rosemount 3144P
2-10
Multichannel Installation
(HART / 4–20 mA only)
You can connect several transmitters to a single master power supply (see
Figure 2-7). 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 2-7 prevent unwanted
charging or discharging of the back-up battery.
Figure 2-7. Multichannel
Installations.
WIRING
HART / 4–20 mA Field Wiring
All 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 the best
results. Do not run unshielded signal wiring in conduit or open trays with
power wiring or near heavy electrical equipment. High voltage may be present
on the leads and may cause electrical shock. To wire the transmitter for
power, follow the steps below.
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 2-8.
Crimped lugs are recommended when wiring to screw terminals.
3. Tighten the terminal screws to ensure that good contact is made. No
additional power wiring is required.
4. Replace the transmitter covers. Both transmitter covers must be fully
engaged to meet explosion-proof requirements.
NOTE
Do not apply high voltage (e.g., ac line voltage) to the transmitter terminals.
Abnormally high voltage can damage the unit.
Transmitter
No. 1
Readout or
Controller No. 1
Transmitter
No. 2
Readout or
Controller No. 2
Battery
Backup
To Additional
Transmitters
dc
Power
Supply
3044-0131A
Between 250 and 1100 Ω
If No Load Resistor
R
Lead
R
Lead
R
Lead