Rosemount 3491, Reference Manual, Page: 35 / 152

Reference Manual
00809-0100-4841, Rev. AA
May 2007
4-3
Rosemount 3490 Series
NOTE:
If being used for the first time with a Rosemount 3100 Series transmitter, there
will be a prompt for the Bottom Reference of the transmitter. This value will
then be used to automatically set-up the transmitter 4-20mA output span over
this range.
If you do not want to commission the system now, simply switch off the power
and the same prompt will re-appear when switching on the next time.
If you are commissioning the system now, edit the Bottom Reference with the
arrow buttons and then press the red (ENTER) button to confirm the
programmed value. The Bottom Reference can be changed at a later stage,
but it is better to get it correct now. If you press the ESC button, the start-up
process will continue and the Bottom Reference prompt will re-appear when
switching on the next time.
After the start-up process is complete, the Primary Display appears showing a
measurement e.g. depth of the liquid in the tank. The value on the Primary
Display is the 3490’s PV (Primary Variable).
Whenever the 3490 Series Control Unit is switched off and then on, it will
re-establish digital communications with the HART transmitter and then the
Primary Display will appear.
Continue with a tour of the hierarchical menu system on page 4-5, or turn to
the Section “Programming“ on page 4-9.
Switching-on the 3492
Model 3492 of the Rosemount 3490 Series Control Units takes the input from
two HART transmitters and will perform various calculations to create a single
sum, difference or product of the two inputs.
Figure 4-2.
3492 and two HART transmitters
It is important to connect the two HART transmitters in the correct sequence ,
as detailed in “Connecting HART Transmitters to 3492“ on page 3-10.
After both HART transmitters are connected, the top-left corner shows
communications with both transmitters by alternating "1" and "2" next to the
digital communications icon.
The actual PV shown on the display remains that of Tx1, which is the factory
default condition. You will be able to change this to another value, usually the
sum, difference or product of the two transmitter readings at a later stage.