Measuring Cell For Level - Siemens SITRANS P DS III Operating Instructions Manual

Description
3.7 Principle of operation
3.7.3.3

Measuring cell for level

①
②
③
④
⑤
Image 3-7
● The inlet pressure (hydrostatic pressure) works hydraulically on the measuring cell
through the seal diaphragm
● Differential pressure at the measuring cell is transmitted to the differential pressure
sensor
● When measuring limits are exceeded, the overload diaphragm
the seal diaphragms
⑥ thus protect the differential pressure sensor
● The seal diaphragm
changes the resistance of the four doped piezoresistors in the bridge circuit.
● The change in the resistance causes a bridge output voltage proportional to the
differential pressure.
32
Pressure cap
O-ring
Measuring cell body
Overload diaphragm
Differential pressure sensor
Function chart of the measuring cell for level
⑤
through the seal diaphragms
⑥
or
⑥
is displaced by the differential pressure. The displacement
⑥
Seal diaphragm on the measuring cell
⑦
Filling liquid of the measuring cell
⑧
Capillary tube with the fill fluid of the mounting
flange
⑨
Flange with a tube
⑩
Seal diaphragm on the mounting flange
⑩
on the mounting flange
⑥
and the filling liquid
⑩
rests on the measuring cell body
⑤
Operating Instructions, 02/2016, A5E00053276-08
⑩
.
⑦
.
④
is displaced until one of
③
. The seal diaphragms
from overload.
SITRANS P DS III/P410 with PROFIBUS PA