Diagnostic Messages; Hardware - Emerson Rosemount 248 Reference Manual

Reference Manual
00809-0100-4825, Rev CB
4.4

Diagnostic messages

4.4.1

Hardware

If a malfunction is suspected, despite the absence of diagnostics messages on the Field
Communicator display, follow the procedures described in
hardware and process connections are in good working order. Under each of four major
symptoms, specific suggestions are offered for solving the problem.
Table 4-1. Rosemount 248 Troubleshooting Chart
Potential
Symptom source
Transmitter Loop Wiring
Does Not
Communicate
with Field
Communicator
High Output Sensor Input
Failure or
Connection
Loop Wiring
Power Supply
Electronics
Module
Erratic Output Loop Wiring
Electronics
Module
Operation and Maintenance
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.

Check for dirty or defective terminals, interconnecting pins, or

receptacles.
Check the output voltage of the power supply at the transmitter

terminals. It should be 12.0 to 42.4 V dc (over entire 3.75 to 23 mA
operating range).
Connect a Field Communicator and enter the transmitter status mode

to isolate module failure.
Connect a 375 Field Communicator and check the sensor limits to

ensure calibration adjustments are within the sensor range.
Check for adequate voltage to the transmitter. It should be 12.0 to

42.4 V dc at the transmitter terminals (over entire 3.75 to 23 mA
operating range).
Check for intermittent shorts, open circuits, and multiple grounds.

Connect a Field Communicator and enter the Loop test mode to

generate signals of 4 mA, 20 mA, and user-selected values.
Connect a Field Communicator and enter the transmitter test mode to

isolate module failure.
Section 4: Operation and Maintenance
Table 4-1 to verify that transmitter
March 2014
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