Emerson Rosemount 3144P, Справочное руководство

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24
Reference Manual
00809-0100-4021, Rev JA
Installation
April 2017
Installation
RTD or ohm inputs
If the transmitter is mounted remotely from a 3- or 4-wire RTD, it will operate within specifications,
without recalibration, for lead wire resistances of up to 60 ohms per lead (equivalent to 1,000 ft. of
20 AWG wire). In this case, the leads between the RTD and transmitter should be shielded. If using only
two leads (or a compensation loop lead wire configuration), both RTD leads are in series with the sensor
element, so significant errors can occur if the lead lengths exceed one foot of 20 AWG wire. For longer
runs, attach a third or fourth lead as described above. To eliminate 2-wire lead resistance error, the
2-wire offset command can be used. This allows the user to input the measured lead wire resistance,
resulting in the transmitter adjusting the temperature to correct the error.
When using Rosemount X-well Technology, the Rosemount 3144P Temperature Transmitter is required
to be assembled to a Rosemount 0085 Pipe Clamp RTD Sensor in a direct mount 4-wire configuration. It
can be changed to 3- or 2-wired configuration, if required, in the field.
Thermocouple or millivolt inputs
For direct-mount applications, connect the thermocouple directly to the transmitter. If mounting the
transmitter remotely from the sensor, use appropriate thermocouple extension wire. Make connections
for millivolt inputs with copper wire. Use shielding for long runs of wire.
Note
For HART transmitters, the use of two grounded thermocouples with a dual option transmitter is not
recommended. For applications in which the use of two thermocouples is desired, connect either two
ungrounded thermocouples, one grounded and one ungrounded thermocouple, or one dual element
thermocouple.
2.7 Power supply
HART
An external power supply is required to operate the transmitter (not included). The input voltage range
of the transmitter is 12 to 42.4 Vdc. This is the power required across the transmitter power terminals.
The power terminals are rated to 42.4 Vdc. With 250 ohms of resistance in the loop, the transmitter
requires a minimum of 18.1 Vdc for communication.
The power supplied to the transmitter is determined by the total loop resistance and should not drop
below the lift-off voltage. The lift-off voltage is the minimum supply voltage required for any given total
loop resistance. See
Figure 2-16 to determine the required supply voltage. If the power drops below the
lift-off voltage while the transmitter is being configured, the transmitter may output incorrect
information.
The dc power supply should provide power with less than 2 percent ripple. The total resistance load is the
sum of the resistance of the signal leads and the load resistance of any controller, indicator, or related
piece of equipment in the loop. Note that the resistance of intrinsic safety barriers, if used, must be
included.
Note
Permanent damage to the transmitter could result if the voltage drops below 12.0 Vdc at the power
terminals, when changing transmitter configuration parameters.