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Reference Manual
00809-0100-4514, Rev BA
January 2008
Rosemount 1154
4-2
K
1
is a constant.
C
1
is the capacitance between the high pressure side and the sensing
diaphragm.
C
2
is the capacitance between the low pressure side and the sensing
diaphragm.
Where:
I
ref
is the current source.
V
p-p
is the peak-to-peak oscillation voltage.
f is the oscillation frequency.
Where:
I
diff
is the difference in current between C
1
and C
2
.
Therefore:
Figure 4-1. The
δ-Cell.
fV
pp–
I
ref
C
1
C
2
+
--------------------=
I
diff
fV
pp–
C
2
C
1
–()=
P Constant I
diff
× I
ref
C
2
C
1
–
C
2
C
1
+
--------------------
⎝⎠
⎜⎟
⎛⎞
==
Leadwires
Isolating
Diaphragm
Welded Seals
Capacitor
Plates
Sensing
Diaphragm
Rigid
Insulation
Silicone Oil