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Reference Manual
00809-0100-4021, Rev DA
November 2004
1-3
Rosemount 3144P
Environmental 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 1-1 describes
the relationship between housing temperature rise and extension length.
Figure 1-1. 3144P Transmitter
Housing Temperature Rise
versus Extension Length for a
Test Installation.
Example:
The maximum permissible housing temperature rise (T) can be calculated
by subtracting the maximum ambient temperature (A) from the
transmitter’s ambient temperature specification limit (S). For instance,
suppose A = 40 °C.
T = S - A
T = 85 °C – 40 °C
T = 45 °C
For a process temperature of 540 °C (1004 °F), an extension length of 3.6
inches (91.4 mm) yields a housing temperature rise (R) of 22 °C (72 °F),
which provides a safety margin of 23 °C (73 °F). A six-inch extension
length (R = 10 °C (50 °F)) would offer a higher safety margin (35 °C (95
°F)) and would reduce temperature-effect errors but would probably
require extra transmitter support. Gauge the requirements for individual
applications along this scale. If a thermowell with lagging is used, the
extension length may be reduced by the length of the lagging.
Moist or Corrosive
Environments
The 3144P temperature transmitter has a highly reliable dual compartment
housing designed to resist moisture and corrosion. The sealed electronics
module is mounted in a compartment that is isolated from the terminal side
conduit entries. O-ring seals protect the interior when the covers are properly
installed. In humid environments, however, it is possible for moisture to
accumulate in conduit lines and drain into the housing.
Housing Temperature Rise, Above
Ambient °C (°F)
3 4 5 6 7 8 9
0
60 (108)
50 (90)
40 (72)
30 (54)
20 (36)
10 (18)
3.6
22
Extension Length (in.)
3044-0123A
815 °C (1500 °F) Oven Temperature
540 °C (1000 °F)
Oven Temperature
250 °C (482 °F) Oven Temperature