Surges/Transients; Grounding - Emerson Rosemount 3144P Reference Manual

Reference Manual
00809-0100-4021, Rev JA
Figure 2-16. Load Limits
Maximum load = 40.8
1240
1100
1000
750
500
250
0
F
OUNDATION
Powered over F
between 9.0 and 32.0 Vdc, 11 mA maximum. Transmitter power terminals are rated to 42.4 Vdc.
The power terminals on the Rosemount 3144P with F
2.7.1

Surges/transients

The transmitter will withstand electrical transients of the energy level usually encountered in static
discharges or induced switching; however, high-voltage transients, such as those induced in wiring from
nearby lightning strikes, can damage both the transmitter and the sensor.
The integral transient protection terminal block (option code T1) protects against high-voltage
transients. The integral transient protection terminal block is available as an ordered option, or as an
accessory. Refer to
2.7.2

Grounding

Sensor shielding
The currents in the leads induced by electromagnetic interference can be reduced by shielding. Shielding
carries the current to ground and away from the leads and electronics. If the ends of the shields are
adequately grounded, only a small amount of current will actually enter the transmitter.
If the ends of the shield are left ungrounded, voltage is created between the shield and the transmitter
housing and also between the shield and earth at the element end. The transmitter may not be able to
compensate for this voltage, causing it to lose communication and/or go into alarm. Instead of the shield
carrying the currents away from the transmitter, the currents will now flow through the sensor leads into
the transmitter circuitry where it will interfere with the circuit operation.
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 representative.
Installation
(Supply voltage–12.0)
4–20 mA dc
Operating
region
10 20 30 40 42.4
12.0
Supply voltage (Vdc)
Fieldbus
Fieldbus with standard Fieldbus power supplies, the transmitter operates
OUNDATION
"Transient protection (option code T1)" on page 185
Fieldbus are polarity insensitive.
OUNDATION
for more information.
Installation
April 2017
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