
3.6.3.4 Measuring cell for absolute pressure from the differential pressure series
① Pressure cap ⑥ Overload diaphragm
② Seal diaphragm on the measuring cell ⑦ Measuring cell filling liquid
③ O-ring ⑧ Reference pressure
④ Measuring cell body p
e
Pressure input variable
⑤ Absolute pressure sensor
Figure 3-10 Function chart of measuring cell for absolute pressure
●
Absolute pressure is transmitted to the absolute pressure sensor ⑤ through the seal
diaphragm ② and the filling liquid ⑦.
● When measuring limits are exceeded, the overload diaphragm ⑥ is displaced until the seal
diaphragm ② rests on the measuring cell body ④. The seal diaphragm thus protects the
absolute pressure sensor ⑤ from overload.
● The difference between the inlet pressure (p
e
) and the reference pressure ⑧ on the
negative side of the measuring cell displaces the seal diaphragm ②. The displacement
changes the resistance of the four piezoresistors (bridge circuit) of the absolute pressure
sensor.
Description
3.6 Functional principle
SITRANS P, DS III series with HART
28 Operating Instructions, 09/2012, A5E00047092-08
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