Rosemount 1199, Справочное руководство

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Reference Manual
00809-0100-4002, Rev BB
November 2012
Rosemount 1199
4-8
TRANSMITTERS
INSTALLATION BEST
PRACTICES
Pressure transmitters have a sensor module with a primary fill fluid.
Therefore, the mounting position of a standard transmitter with silicon fill could
read approx ± 1.25inH
2
0 worst case after installation. This is simply zeroed
out using a HART field communicator after installation so that it will read zero
pressure. With a remote seal attached you have additional components that
will create additive pressure that would increase the amount of potential shift.
This would include the secondary fill fluid in the remote seal assembly along
with the potential of torquing effects when the assembly is bolted to the
process. For these reasons, the transmitter’s digital output will most likely not
match the exact values calculated on paper. Even a redundant transmitter
would most likely not read the exact digital values after being installed. For
these reasons, a re-range function is common practice after all installations.
What’s important is the calculated span (level height X Specific gravity of the
process). After the transmitter is mounted, it is common and best practice to
re-range the transmitter so that the 4m point will be the installed digital value.
The 20mA point would then be set based on the calculated span value setting
it above the installed digital value.
The procedure would be based on mounting configuration (Zero based) 4mA
= 0in H
2
O or (Non Zero base) 4mA exceeds the ± 3% of the Upper Sensor
Limit.
OPEN TANK (Zero
Based)
With open tank level applications this value can typically be zeroed out using
a HART device as long as it is <3% USL. The maximum value that can be
zeroed out is 3% of the Upper Sensor Limit or 7.5in H20 for a range 2 (250in
H20) sensor.
CLOSED TANK (Non
Zero Based)
For closed tank level applications this value is most likely too high and cannot
be zeroed out due to the applied pressure of the secondary fill fluid. For this
reason, the transmitter would simply be re-ranged so that the 0% value (4mA)
would equal the installed value. The 100%, (20mA) would be adjusted to the
required calculated span.
Primary Fill
Secondary Fill
PRESSURE TRANSMITTER WITH
REMOTE SEAL
PRESSURE TRANSMITTER
Primary Fill