Tip
Use an external device only if it is more accurate than the internal RTD.
Important
Line temperature data is used in several different measurements and calculations. It is possible to
use the internal RTD temperature in some areas and an external temperature in others. The
transmitter stores the internal RTD temperature and the external temperature separately. However,
the transmitter stores only one alternate temperature value, which may be either an external
temperature or the configured fixed value. Accordingly, if you set up polling for temperature in one
area, and digital communications in another, and configure a fixed temperature value in a third, the
fixed value will be overwritten by polling and digital communications, and polling and digital
communications will overwrite each other.
Procedure
Choose the method to be used to supply temperature data, and perform the required
setup.
Option Description Setup
Internal RTD tem-
perature data
Temperature data from the on-
board temperature sensor
(RTD) is used.
a. Set Line Temperature Source to Internal RTD.
b. Click Apply.
Polling The meter polls an external de-
vice for temperature data. This
data will be available in addi-
tion to the internal RTD tem-
perature data.
a. Set Line Temperature Source to Poll for External Value.
b. Set Polling Slot to an available slot.
c. Set Polling Control to Poll as Primary or Poll as Secondary.
Option Description
Poll as Primary No other HART masters will be on the
network. The Field Communicator is not
a HART master.
Poll as Secondary Other HART masters will be on the net-
work. The Field Communicator is not a
HART master.
d. Set External Device Tag to the HART tag of the temperature
device.
e. Click Apply.
Digital communica-
tions
A host writes temperature data
to the meter at appropriate in-
tervals. This data will be availa-
ble in addition to the internal
RTD temperature data.
a. Set Line Temperature Source to Fixed Value or Digital Communica-
tions.
b. Click Apply.
c. Perform the necessary host programming and communica-
tions setup to write temperature data to the meter at appro-
priate intervals.
Configure process measurement
28 Micro Motion
®
Fork Density Meters (FDM)
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