Emerson Rosemount 644h, Справочное руководство

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Reference Manual
00809-0100-4728, Rev HA
December 2002
Models 644H and 644R
4-6
Scaled Output Trim
The Scaled D/A Trim command matches the 4 and 20 mA points to a
user-selectable reference scale other than 4 and 20 mA (2–10 volts, for
example). To perform a scaled D/A trim, connect an accurate reference
meter to the transmitter and trim the output signal to scale as outlined in
the ”Output Trim” procedure.
HARDWARE
Maintenance
The Model 644H has no moving parts and requires minimal scheduled
maintenance.
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.
Select any standard, off-the-shelf sensor for use with a Model 644, or consult
the factory for a replacement special sensor and transmitter combination.
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. Model 644H
Troubleshooting Chart
Fast Key Sequence 1, 2, 2, 3
Symptom Potential Source Corrective Action
Transmitter Does
Not Communicate
with HART
Communicator Loop Wiring
• Check the revision level of the transmitter device descriptors (DDs) stored in the communicator.
The communicator should report Dev v6, DD v1.
• Check for a minimum of 250 ohms resistance between the power supply and Model 275 HART
Communicator connection.
• Check for adequate voltage to the transmitter. If a Model 275 HART 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 Model 275 HART 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).