Considerations; General; Electrical; Mechanical - Emerson Rosemount 3144P Reference Manual

Reference Manual
00809-0100-4021, Rev AA
March 2002

CONSIDERATIONS

General

Electrical

Mechanical

Environmental

Electrical temperature sensors, such as resistance temperature detectors
(RTDs) and thermocouples (T/Cs), produce low-level signals proportional to
temperature. The Model 3144P transmitter converts low-level sensor signals
to a standard 4–20 mA dc signal. This current signal is then transmitted to the
control room via two power/signal wires.
Figures 2-6 and 2-7 show recommended mounting configurations for
transmitters and sensor assemblies.
Proper electrical installation is essential to prevent errors due to sensor lead
resistance and electrical noise. Shielded cable should be used for best results
in electrically noisy environments. The current loop must have between 250
and 1100 ohms in order to communicate with a HART communicator. Refer to
Figure 2-10 on page 2-13 for sensor and current loop connections.
Use the following information when preparing the installation site and
selecting transmitter options.
The transmitter may be mounted directly to or remotely from the sensor.
Using optional mounting brackets, the transmitter may be mounted to a flat
surface or to a two-inch diameter pipe (see "Optional Transmitter Mounting
Brackets" on page A-8).

Temperature Effects

The transmitter will operate within specifications for ambient temperatures
between –40 and 185 °F (–40 and 85 °C). Heat from the process is
transferred from the thermowell to the transmitter housing. If the expected
process temperature is near or beyond specification limits, consider the use of
additional thermowell lagging, an extension nipple, or a remote mounting
configuration to isolate the transmitter from the process. Figure 2-4 describes
the relationship between transmitter housing temperature rise and extension
length.
Model 3144P
2-3