20
Reference Manual
00809-0100-4021, Rev GC
Section 2: Installation
April 2014
Installation
2.4.5 Multichannel installation (HART / 4–20 mA only)
Several transmitters can be connected to a single master power supply (see Figure 2-8). 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 2-8 prevent unwanted charging or discharging of
the back-up battery.
Figure 2-8. Multichannel Installations
2.5 Wiring
2.5.1 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 2-9. 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.
Note
Do not apply high voltage (e.g., AC line voltage) to the power or sensor terminals, since 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
Between 250 and 1100 If
No Load Resistor
R
Lead
R
Lead
R
Lead
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