2-11
Installation
ENVIRONMENTAL
CONSIDERATIONS
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 2-11 describes the relationship between
transmitter housing temperature rise and extension length.
Figure 2-10. Model 3144/3244MV
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.
For a process temperature of 540 °C (see Figure 2-10), an extension
length of 3.6 inches yields a housing temperature rise (R) of 22 °C,
which provides a safety margin of 23 °C. A six-inch extension length
(R = 10 °C) would offer a higher safety margin (35 °C) and would
reduce temperature-effect errors but would probably require extra
support for the transmitter. 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.
HOUSI
N
G
T
EMPERA
T
URE
RI
SE
ABO
VE
AMBI
ENT
°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
Transmitter Housing
Temperature Rise vs.
Extension Length for a
Test Installation
EXTENSION LENGTH (IN.)
30
44-
0123
A
54
0
°C
250
°C
Oven Temperature
(1,0
00
°F)
8
1
5
°C
(1
,5
00
°F
)
Ov
en
Temp
eratu
re
(482°F)
Oven
Tempera
ture
T
S
A
–
=
T
85 °C
40 °C
–
=
T
45 °C
=
