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Reference Manual
00809-0100-4690, Rev EA
March 2007
Rosemount 2088 and 2090
3-12
Figure 3-9. Transmitter
Load Limitations
Field Wiring All power to the transmitter is supplied over the signal wiring. Signal wiring
need not be shielded, but use twisted pairs for best results. Do not run
unshielded signal wiring in conduit or open trays with power wiring, or near
heavy electrical equipment. For high EMI/RFI environments, shielded twisted
pair cable should be used. To power the transmitter, connect the positive
power lead to the terminal marked “PWR/COMM+” and the negative power
lead to the terminal marked “–” (see Figure 3-10). Tighten the terminal screws
to ensure that proper contact is made. Avoid contact with the leads and the
terminals. No additional power wiring is required for transmitters with
4-20 mA output. For low power transmitters, connect positive signal lead to
“test +” and negative signal lead to terminal marked “-.”
To connect test equipment for monitoring the output of the Rosemount 2088
Smart during maintenance procedures, connect one lead to the terminal
labeled “TEST+” and the other lead to the terminal labeled “–” (see Figure
3-10). Avoid contact with the leads and the terminals.
Signal wiring may be grounded at any one point on the measurement loop, or
it may be left ungrounded. The negative side of the power supply is a
recommended grounding point. The transmitter case may be grounded or left
ungrounded.
Conduit connections at the transmitter should be sealed to prevent moisture
accumulating in the field terminal side of the transmitter housing. Also, install
wiring with a drip loop with the bottom of the drip loop lower than the conduit
connection of the transmitter housing.
(1) For CENLEC EX ia Approval, power supply must not exceed 30 volts.
NOTE
Minimum load impedance for Output Code N is 100 kilohms.
Operating
Region
Max. Load = 45.4 (Power Supply Voltage) –10.5
10.5 15 20 25 30
(1)
36
POWER SUPPLY (DC VOLTS)
LOAD (OHMS)
1158
1000
800
600
400
200
0