Maintenance; Test Terminal; Sensor Checkout - Emerson Rosemount 3144P Reference Manual

Reference Manual
00809-0100-4021, Rev AA
March 2002

Maintenance

POTENTIAL
SYMPTON SOURCE
Low Output or Sensor Element
No Output
Loop Wiring
Electronics Module
The Model 3144P transmitter has no moving parts and require a minimum
amount of scheduled maintenance. The transmitter features modular design
for easy maintenance. If a malfunction is suspected, check for an external
cause before performing the diagnostics as discussed later in this section.
Refer to "Return of Materials" on page 1-3 to return failed transmitters or parts
to a Rosemount Service Center for inspection, repair, or replacement.

Test Terminal

The test terminal, marked as TEST or T on the terminal block, and the
negative terminal accept MINIGRABBER
in-process checks (see Figure 2-9 on page 2-12). The test and the negative
terminals are connected across a diode through which the loop signal current
passes. The current measuring equipment shunts the diode when connected
across the test and negative terminals; so long as the voltage across the
terminals is kept below the diode threshold voltage, no current passes
through the diode. To ensure that there is no leakage current through the
diode while making a test reading, or while an indicating meter is connected,
the resistance of the test connection or meter should not exceed 10 ohms. A
resistance value of 30 ohms will cause an error of approximately 1.0 percent
of reading.

Sensor Checkout

If the sensor is installed in a high-voltage environment and a fault condition or
installation error occurs, the sensor leads and transmitter terminals could
carry lethal voltages. Use extreme caution when making contact with the
leads and terminals.
To determine whether the sensor is at fault, either replace it with another
sensor or connect a test sensor locally at the transmitter to test remote sensor
wiring. Transmitters with Option Code C7 (Trim to Special Sensor), are
matched to a specific sensor. Select any standard, off-the-shelf sensor for use
with the transmitter, or consult the factory for a replacement special
sensor/transmitter combination.
Model 3144P
CORRECTIVE ACTION
• Connect a HART communicator and enter the
transmitter test mode to isolate a sensor failure.
• Check if the process variable is out of range.
• Check for adequate voltage to the transmitter. It
should be 12.0 to 42.4 V dc (over entire 3.90 to 20.5
mA operating range).
• Check for shorts and multiple grounds.
• Check for proper polarity at the signal terminal.
• Check the loop impedance.
• Connect a HART communicator and enter the loop
test mode.
• Check wire insulation to detect possible shorts to
ground.
• Connect a HART communicator and check the sensor
limits to ensure calibration adjustments are within the
sensor range.
• Connect a HART communicator and enter the
transmitter test mode to isolate an electronics
module failure.
™
, or alligator clips, and facilitate
4-3