Measuring Cell For Differential Pressure And Flow Rate - Siemens SITRANS P Operating Instructions Manual

4.4.2.6

Measuring cell for differential pressure and flow rate

①
②
③
④
⑤
Figure 4-12
● Differential pressure is transmitted to the differential pressure sensor
diaphragms
● When measuring limits are exceeded, the seal diaphragm
diaphragm rests on the measuring cell body
protected against overloading since no further deflection of the overload diaphragm
possible.
● The seal diaphragm
the resistance of the four piezoresistors (bridge circuit) of the differential pressure sensor.
● The change in the resistance causes a bridge output voltage proportional to the differential
pressure.
SITRANS P320/P420 with 4 to 20 mA/HART
Operating Instructions, 11/2019, A5E44852162-AC
Inlet pressure P
+
Pressure cap
O-ring
Measuring cell body
Overload diaphragm
Function chart of the measuring cell for differential pressure and flow rate
⑦
and the filling liquid
⑦
is displaced by the differential pressure. The displacement changes
⑥
Filling liquid
⑦
Seal diaphragm
⑧
Inlet pressure P
⑨
Differential pressure sensor
⑥
.
⑦
④
. The differential pressure sensor
Description
4.4 Functional principle
-
⑨
through the seal
is displaced until the seal
⑨
is thus
⑤
is
37