60
Reference Manual
00809-0200-4728, Rev SA
Operation and Maintenance
July 2018
Operation and Maintenance
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, Ohm, and RTD 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).
Option 1
1. Connect sensor wiring shield to the transmitter housing.
2. Ensure the sensor shield is electrically isolated from surrounding fixtures that may be grounded.
3. Ground signal wiring shield at the power supply end.
A. Sensor wires
B. Transmitter
C. Shield ground point
Option 2
1. Connect signal wiring shield to the sensor wiring shield.
2. Ensure the two shields are tied together and electrically isolated from the transmitter housing.
3. Ground shield at the power supply end only.
To Next Page
Loading...
Need help?
General
