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Rosemount 3150 Series
Reference Manual
00809-0100-4835 Rev BE
February 2018
47
Operation
Figure 4-1 – Block Diagram
THE SENSOR CELL
Process pressure is transmitted through an isolating
diaphragm and silicone oil fill fluid to a sensing diaphragm in
the center of the Sensor. The reference pressure is
transmitted in a like manner to the other side of the sensing
diaphragm. The capacitance plates on both sides of the
sensing diaphragm detect the position of the sensing
diaphragm. The capacitance between the sensing diaphragm
and either capacitor plate ranges from 40 pf to 80 pf
depending on input pressure. An oscillator drives the sensor
current through the transformer windings at roughly 110 kHz
and 20 V
p-p
.