Emerson Rosemount 148, Reference Manual, Page: 8 / 36

Temperature effects
The transmitter will operate within specifications for ambient temperatures between –40
and 85 °C (–40 and 185 °F). Heat from the process is transferred from the thermowell to
the transmitter housing. If the expected process temperature is near or above
specification limits, consider using additional thermowell lagging, and extension nipple, or
a remote mounting configuration to isolate the transmitter from the process.
Figure 1-1 provides an example of the relationship between transmitter housing
temperature rise and extension length.
Figure 1-1: Rosemount 148 Transmitter Connection Head Temperature Rise vs.
Extension Length
Example
The transmitter specification limit is 85 °C (185 °F). If the ambient temperature is 55 °C
(131 °F)and the process temperature to be measured is 800 °C (1472 °F), the maximum
permissible connection head temperature rise is the transmitter specification limit minus
the ambient temperature (moves from 85 to 55 °C), or 30 °C (86 °F).
In this case, an extension of 100 mm (3.94-in.) meets this requirement, but 125 mm (4.92-
in.) provides a margin of 8 °C (46.4 °F), thereby reducing any temperature effects in the
transmitter.
1.4 Return of materials
To expedite the return process in North America, call the Emerson National Response
Center toll-free at 1-800-654-7768. This center, available 24 hours a day, can assist with
any needed information or materials.
The center will ask for the following information:
• Product model
• Serial numbers
• The last process material to which the product was exposed
Introduction Reference Manual
June 2019 00809-0100-4148
8 www.Emerson.com