Rosemount 248, Reference Manual

Page: 43 / 80

Reference Manual
00809-0100-4825, Rev BB
August 2005
4-5
Rosemount 248
DIAGNOSTIC
MESSAGES
Hardware
If a malfunction is suspected despite the absence of diagnostics messages on
the HART 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 HART
Communicator Loop Wiring
• Check for a minimum of 250 ohms resistance between the power supply and 375 Field
Communicator connection.
• Check for adequate voltage to the transmitter. If a 375 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 375 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 375 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 375 Field Communicator and enter the Loop test mode to generate signals of 4 mA, 20
mA, and user-selected values.
Electronics
Module
• Connect a 375 Field Communicator and enter the transmitter test mode to isolate module failure.
Low Output or No
Output Sensor Element
• Connect a 375 Field Communicator and enter the Transmitter test mode to isolate a
sensor failure.
• Check the process variable to see if it is out of range.
Loop Wiring
• Check for adequate voltage to the transmitter. It should be 12.0 to 42.4 V dc (over entire 3.75 to
23 mA operating range).
• Check for shorts and multiple grounds.
• Check for proper polarity at the signal terminal.
• Check the loop impedance.
• Connect a 375 Field Communicator and enter the Loop test mode.
• Check wire insulation to detect possible shorts to ground.
Electronics
Module
• Connect a 375 Field Communicator and check the sensor limits to ensure calibration adjustments
are within the sensor range.
• Connect a 375 Field Communicator and enter the Transmitter test mode to isolate an electronics
module failure.