Rosemount 248, Reference Manual

Page: 19 / 80

Reference Manual
00809-0100-4825, Rev BB
August 2005
2-9
Rosemount 248
If the sensor is installed in a high-voltage environment and a fault condition or
installation error occurs, the sensor leads and transmitter terminals could
carry lethal voltages. Use extreme caution when making contact with the
leads and terminals.
NOTE
Do not apply high voltage (e.g., ac line voltage) to the transmitter terminals.
Abnormally high voltage can damage the unit. (Sensor and transmitter power
terminals are rated to 42.4 V dc.) Use extreme caution when making contact
with the leads and terminals.
For multichannel installations, see above. The transmitters will accept inputs
from a variety of RTD and thermocouple types. Refer to Figure 2-7 on
page 2-10 when making sensor connections.
Use the following steps to wire the transmitter:
1. Remove the terminal block cover (if applicable).
2. Connect the positive power lead to the “ + ” terminal. Connect the
negative power lead to the “ – ” terminal (see Figure 2-6). Use extreme
caution when making contact with the leads and terminals.
3. Tighten the terminal screws.
4. Reattach and tighten the cover (if applicable). All connection head
covers must be fully engaged to meet explosion-proof requirements
.
5. Apply power (see “Power Supply”).
Figure 2-6. Rosemount 248
Wiring
Sensor Connections
The Rosemount 248 is compatible with a number of RTD and thermocouple
sensor types. Figure 2-7 shows the correct input connections to the sensor
terminals on the transmitter. To ensure a proper sensor connection, anchor
the sensor lead wires into the appropriate compression terminals and tighten
the screws. Use extreme caution when making contact with the leads and
terminals.
Power, Communication and
Sensors Terminals Connecting a Communicator to a Transmitter Loop
Note: Signal loop may be grounded at any single point or left ungrounded.
Note: A 375 Field Communicator may be connected at any termination point in the signal loop. The
signal loop must have between 250 and 1100 ohms load for communications.
44.0 (1.7)
33 (1.3)
12.9 (0.51)
24.5 (0.97)
250
≤
R
L
≤
1100
Power
Supply
HART Communicator