Rosemount 1199, Справочное руководство

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Reference Manual
00809-0100-4002, Rev BB
November 2012
Rosemount 1199
4-6
Figure 4-5. Balanced system
L
min
= the minimum level of process and typically the 4mA lower range value
L
max
= the maximum level of process and typically the 20mA upper range
value
SG = Specific gravity of the process
Sg = Specific gravity of the remote fill fluid
Hd = Capillary vertical distance going to high side sensor
Ld = Capillary vertical distance going to low side sensor
Tank span = (L
max
x SG)
Example B
Tank Span: 108in X 0.75 = 81inH
2
O
4mA = L
min
x SG + (Ld x Sg) + (Hd x Sg)
= (0 x 0.75) + (60 in. x 0.934) + (60 in. x 0.934)
= -112.08 inH
2
O
NOTE
Pressure (Ld) is applied to Low sensor side and will register as a negative
digital pressure. Pressure (Hd) is pulling down on the high sensor side
therefore would also register as a negative digital pressure therefore these
values are additive.
20mA = L
max
x SG + (Ld X 0.934) + (Hd X 0.934)
= (108 in. x 0.75) + (60 in. x 0.934) + (60 in. x 0.934)
= -31.08 inH
2
O
SPAN = 81 inH
2
O (-112.08 to -31.08 inH
2
O)
NOTE
Silicone 200 has a specific gravity of 0.934.