Emerson Network Router - Manual (Page 63)

Installation and Use Manual 57
Transmitter Configuration, Characterization, and Calibration
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5.8 Configuring polling
Polling is used to retrieve temperature or pressure data from an external device. These data can then
be used for API calculation or other process variable calculations in applications that require pressure
or temperature compensation. You may query one or two external devices.
You must also ensure that the primary mA output has been wired for HART protocol. See Chapter 2
or the installation manual for your transmitter.
To configure polling:
1. From the View menu, select Preferences .
a. To use the external pressure data, ensure that the Enable External Pressure
Compensation check box is checked.
b. To use the external temperature data, ensure that the Use External Temperature check
box is checked.
c. Click Apply .
2. Ensure that the External Temperature box in the Temperature tab has not been set. The
default value is 32.00 °F (0.0000 °C).
3. Click the Polled Variables tab in the Configuration panel.
4. For Polled Variable 1:
a. Click the arrow in the Polling Control box, and select a HART polling method from the
list. Choose Poll DP HART Primary if the external device might be accessed by another
device acting as a secondary master (e.g., a HART Communicator). Choose Poll DP
HART Secondary if the external device might be accessed by another device acting as a
primary master.
b. Click Apply . Polling parameters are now displayed for configuration.
c. In the External Tag box, type the HART tag of the external device that you will poll.
d. Click the arrow in the Variable Type box, and select a process variable.
e. Click Apply .
f. The value displayed in the Current Value textbox is the value received from the external
device. Verify the value.
5. Repeat these steps for Polled Variable 2, if required.
Note: For some transmitters, the Polling Control selection for Polled Variable 1 is automatically used
for Polled Variable 2. No configuration is required.