Emerson Rosemount 248, Справочное руководство

Страница: 55 / 92

47
Reference Manual
00809-0100-4825, Rev CB
Section 4: Operation and Maintenance
March 2014
Operation and Maintenance
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
Table 4-1 to verify that 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 4-1. Rosemount 248 Troubleshooting Chart
Symptom
Potential
source
Corrective action
Transmitter
Does Not
Communicate
with Field
Communicator
Loop Wiring

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.
High Output Sensor Input
Failure or
Connection

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.
Loop Wiring

Check for dirty or defective terminals, interconnecting pins, or
receptacles.
Power Supply

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).
Electronics
Module

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.
Erratic Output Loop Wiring 
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.
Electronics
Module

Connect a Field Communicator and enter the transmitter test mode to
isolate module failure.