170
Reference Manual
00809-0100-4021, Rev JA
Operation and Maintenance
April 2017
Operation and Maintenance
5.2.1
Test terminal (HART
®
/4–20 mA only)
The test terminal, marked as TEST or (“T”) on the terminal block, and the negative (–) terminal accept
MINIGRABBER
™
, or alligator clips, facilitate in-process checks (see
). The test and
the negative terminals are connected across a diode through the loop signal current. The current
measuring equipment shunts the diode when connected across the test (T) and negative (–) terminals;
so as long as the voltage across the terminals is kept below the diode threshold voltage, no current
passes through the diode. To ensure 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.
5.2.2
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, 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 a standard, off-the-shelf sensor for use with the
transmitter, or consult the factory for a replacement special sensor/transmitter combination.
5.2.3
Electronics housing
The transmitter is designed with a dual-compartment housing. One compartment contains the
electronics module, and the other contains all wiring terminals and communication receptacles.
Removing the electronics module
Note
The electronics are sealed in a moisture-resistant plastic enclosure referred to as the electronics module.
This module is a non-repairable unit and the entire unit must be replaced if a malfunction occurs.
The transmitter electronics module is located in the compartment opposite the wiring terminals.
Use the following procedure to remove the electronics module:
1. Disconnect the power to the transmitter.
2. Remove the cover from the electronics side of the transmitter housing (see
). Do not remove the covers in explosive atmospheres with a live circuit. Remove
the LCD display, if applicable.
3. Loosen the two screws anchoring the electronics module assembly to the transmitter housing.
4. Firmly grasp the screws and assembly and pull straight out of the housing, taking care not to damage
the interconnecting pins.
Note
If you are replacing the electronics module with a new one, make sure that the alarm switches are set in
the same positions.
Summary of Contents for Rosemount 3144P
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Page 10: ...8 Reference Manual 00809 0100 4021 Rev JA Title Page April 2017 Title Page ...
Page 16: ...6 Reference Manual 00809 0100 4021 Rev JA Introduction April 2017 Introduction ...
Page 38: ...28 Reference Manual 00809 0100 4021 Rev JA Installation April 2017 Installation ...
Page 235: ...225 Reference Manual 00809 0100 4021 Rev JA April 2017 ...
