Hardware Maintenance; Diagnostic Messages - Emerson Rosemount 248 Reference Manual

Operation and Maintenance
May 2019
4.5

Hardware Maintenance

The Rosemount 248 has no moving parts and requires minimal scheduled maintenance.
4.5.1 Sensor checkout
To determine whether the sensor is at fault, replace it with another sensor or connect a
test sensor locally at the transmitter to test remote sensor wiring. Do not remove the
thermowell while in operation. Select any standard, off-the-shelf sensor for use with a
Rosemount 248, or consult the factory for a replacement special sensor and transmitter
combination.
4.6

Diagnostic messages

4.6.1 Hardware troubleshooting
If a malfunction is suspected, despite the absence of diagnostics messages on the Field
Communicator display, follow the procedures described in
transmitter hardware and process connections are in good working order. Under each of
four major symptoms, specific suggestions are offered for solving the problem.
Table 4-2: Rosemount 248 Troubleshooting Chart
Symptom
Transmitter
Does Not
Communicate
with Field
Communicator
High Output
50
Note
HART Revision 7 is only compatible with AMS Device Manager 10.5, and greater.
AMS Device Manager version 10.5 requires a software patch to be compatible.
Potential source
Loop Wiring
Sensor Input
Failure or
Connection
Table 4-2
Corrective action
• Check for a minimum of 250 ohms resistance between
the power supply and Field Communicator connection.
• Check for adequate voltage to the transmitter. If a Field
Communicator is connected and 250 ohms resistance is
in the loop, the transmitter requires a minimum of
12.0 V at the terminals to operate (over entire 3.75 to
23 mA operating range).
• Check for intermittent shorts, open circuits, and
multiple grounds.
• Specify the transmitter by tag number. For certain non-
standard transmitter installations, it may be necessary,
because of excessive line length, to specify the
transmitter tag number to initiate communications.
• Connect a Field Communicator and enter the
transmitter test mode to isolate a sensor failure.
• Check for a sensor open or short circuit.
• Check the process variable to see if it is out of range.
Rosemount 248 Temperature Transmitter Reference Manual
Reference Manual
00809-0100-4825
to verify that