Emerson Rosemount, Reference Manual

Page: 36 / 252

26
Reference Manual
00809-0100-4021, Rev GC
Section 2: Installation
April 2014
Installation
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 Process Management representa-
tive.
Ungrounded thermocouple, mV, and RTD/ohm Inputs
Option 1: Recommended for ungrounded transmitter housing
1. Connect the 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 the shield at the power supply end only.
4. Ensure the shield at the sensor is electrically isolated from the surrounding fixtures that
may be grounded.
a. Connect shields together, electrically isolated from the transmitter.
Option 2: Recommended for grounded transmitter housing
1. Ground the transmitter housing then connect the sensor wiring shield to the
transmitter housing (see
“Transmitter housing” on page 27 ).
2. Ensure the shield at the sensor end is electrically isolated from surrounding fixtures that
may be grounded.
3. Ground the signal wiring shield at the power supply end.
A. Sensor Wires C. 4-20 mA loop E. DCS
B. Transmitter D. Shield ground point
A. Sensor Wires C. 4-20 mA loop E. DCS
B. Transmitter D. Shield ground point
A
B
D
C
E
A
B
D
C
E
D