Environmental - Emerson Rosemount 248 Reference Manual

Section 1: Introduction
March 2014
1.3.5

Environmental

The transmitter electronics module is permanently sealed within the housing, to resist moisture
and corrosive damage. Verify that the operating atmosphere of the transmitter is consistent
with the appropriate hazardous locations certifications.
Temperature effects
The transmitter operates within specifications for ambient temperatures between –40 and 185
°F (–40 and 85 °C). Process heat from the process is transferred from the thermowell to the
transmitter housing so if the expected process temperature is near or above specification limits,
consider using an additional thermowell lagging, and extension nipple, or a remote mounting
configuration to isolate the transmitter from the process.
Figure 1-1
rise and extension length.
Figure 1-1. Rosemount 248 Transmitter Connection Head Temperature rise vs. Extension
Length
60
50
40
30
20
10
0
Example
The transmitter specification limit is 85 °C. If the ambient temperature is 55 °C and the process
temperature to be measured is 800 °C, the maximum permissible connection head temperature
rise is the transmitter specification limit minus the ambient temperature (moves 85 to 55 °C), or
30 °C.
In this case, an extension of 100 mm meets this requirement, but 125 mm provides a margin of
8 °C, reducing any temperature effects in the transmitter.
4
provides an example of the relationship between transmitter housing temperature
75 10 125 150 175 200
Extension length (mm)
225
Reference Manual
00809-0100-4825, Rev CB
Introduction