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4.6.1 Power Supply
The 3100 Pressure Transmitter requires an 11.9 – 45 VDC power
supply. A 250 ~ 550Ω (24 VDC) loop resistance is recommended
for HART
®
communication. Loop resistance is the sum of the
resistance in the loop.
Max. Loop Resistance [Ω] = (E-11.9) [vdc] / 0.022 [mA]
4.7 Wiring
4.7.1 Wiring Caution
1.
Install the signal cables away from potential sources of
electrical noise such as transformers, electrical motors, etc.
2.
Before wiring, remove electrical conduit cap.
3.
All screwed connections on the housing must be sealed with
waterproof sealant. We recommend use of silicone based
sealants to minimize post-hardening.
4.
Avoid running DC signal and AC power cables in the same
ducts/cable conduits to avoid signal noise issues.
5.
All explosion-proof transmitters must meet the wiring &
installation requirements specified within the applicable
electrical codes.
4.7.2 Selecting the Wiring Materials
1.
Use 600V shielded PVC wire or standard wire
of the same class. (To ensure proper communication use 24
AWG or larger wire, and do not exceed 5000 feet)
2.
Use shielded wire in areas with electrical noise.
3.
In areas with high or low ambient temperatures, use wire or
cable that is rated for the extreme temperatures.
4.
If the wire or cable is going to be used in oil, solvent, toxic
gas or liquid, make sure it is rated accordingly.
5.
Process wire or cable must not be soldered to the terminal
lug. Spade connectors are recommended to connect the
process wires to the transmitter.
4.7.3 Connecting External Wires to Transmitter Terminal Box
1.
Open the cover indicated "FIELD TERMINAL". Do not open
the cover if the transmitter is located in an explosion-proof
area and powered. Connect the power supply to the
terminal indicated "+PWR"(left terminal) and "-" in the
central terminal. Do not connect "+" power supply to "+"
terminal "TEST". It will damage the test diode.
2.
Seal and close the conduit connection to prevent humidity
and explosion-proof atmosphere from entering the housing.
3.
Transmitter power is supplied by signal wire. Do not install
near high voltage wires or high voltage equipment.
4.
Close the transmitter cover. To meet the explosion-proof
ratings make sure the covers are fully engaged.
NOTE: Do not power the transmitter with high voltage (AC).
It can damage the transmitter.
5.
You must connect a 250~550 Ohm Resistor in Current
Loop (between Power Supply and Transmitter) for HART
®
Communication. See Figure 4-2.
4.7.4 Wiring
Warning
Explosion can result in death or serious injury:
• Do not remove the transmitter covers in an
explosion-proof environment when the circuit is
powered.
• Both transmitter covers must be fully engaged to
meet explosion-proof requirements
A.
Loop Configuration
Mercoid
®
3100 Pressure Transmitters use a two-wire
system for power, 4~20mA analog signal transmission and
HART
®
digital transmission.
A DC Power Supply is required for the transmitter loop. The
transmitter and power supply should be connected as
shown below.
COMM
TEST
COMM
TEST
Figure 4-2 Wiring the 3100 Pressure Transmitter
Figure 4-3 Picture of Transmitter Wiring Terminal
COMM
TEST
COMM
TEST
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