Emerson Rosemount 644 Reference Manual page 78

Electrical Installation
March 2021
Shielding recommendations
The following are recommended practices from API Standard 552 (Transmission Standard)
section 20.7, and from field and laboratory testing. If more than one recommendation is
given for a sensor type, start with the first technique shown or the technique that is
recommended for the facility by its installation drawings. If the technique does not
eliminate the transmitter alarms, try another technique. If all of the techniques do not
eliminate or prevent the transmitter alarms because of high EMI, contact an Emerson
representative.
To ensure proper grounding, it is important that the instrument cable shield be:
• Trimmed close and insulated from touching the transmitter housing
• Connected to the next shield if cable is routed through a junction box
• Connected to a good earth ground at the power supply end
Ungrounded thermocouple, mV, and RTD/Ohm inputs
Each process installation has different requirements for grounding. Use the grounding
options recommended by the facility for the specific sensor type, or begin with grounding
option 1 (the most common).
Ground the transmitter: option 1
Procedure
1. Connect sensor wiring shield to the transmitter housing.
2. Ensure the sensor shield is electrically isolated from surrounding fixtures that may
3. Ground signal wiring shield at the power supply end.
78
be grounded.
A
A. Sensor wires
B. Transmitter
C. Shield ground point
D. 4-20 mA loop
Reference Manual
00809-0200-4728
B
C
DCS
D
Emerson.com/Rosemount