Reference Manual
00809-0100-4148, Rev BA
July 2010
1-3
Rosemount 148
CONSIDERATIONS
General
Electrical temperature sensors such as RTDs and thermocouples produce
low-level signals proportional to the sensed temperature. The Rosemount 148
converts the low-level sensor signal to a standard 4–20 mA DC signal that is
relatively insensitive to lead length and electrical noise. This current signal is
transmitted to the control room via two wires.
Mechanical
Location
Take into account the need for access to the transmitter when choosing an
installation location.
Special Mounting
Special hardware is available for mounting a Rosemount 148 head mount
transmitter to a DIN rail.
Electrical
Proper electrical installation is necessary to prevent errors due to sensor lead
resistance and electrical noise. For best results, shielded cable should be
used in electrically noisy environments.
Make wiring connections through the cable entry in the side of the connection
head. Be sure to provide adequate clearance for cover removal.
Environmental
The transmitter electronics module is permanently sealed within the housing,
resisting moisture and corrosive damage. Verify that the operating
atmosphere of the transmitter is consistent with the appropriate hazardous
locations certifications.
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 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.