Siemens SITRANS Series - Measuring Cell for Gauge Pressure

Overview
The following modes of operation are described:
● Gauge pressure
● Absolute pressure
● Differential pressure and flow rate
● Level
The following process connections are available, for example:
● G1/2 B, 1/2-14 NPT
● Male thread: M20
● Flange connection in accordance with EN 61518
● Flush-mounted process connections
4.4.3.1 Measuring cell for gauge pressure
S
H






① Reference pressure opening ⑤ Filling liquid
② Measuring cell ⑥ Gauge pressure sensor
③ Process connection p
e
Inlet pressure
④ Seal diaphragm
Figure 4-7 Function chart of measuring cell for gauge pressure
The inlet pressure (p
e
) is transferred to the gauge pressure sensor ⑥ via the seal diaphragm
④ and the fill fluid ⑤, displacing its measuring diaphragm. The displacement changes the
resistance of the four piezoresistors (bridge circuit) of the gauge pressure sensor. The change
in the resistance causes a bridge output voltage proportional to the inlet pressure.
Pressure transmitters with measuring span ≤ 63 bar measure the inlet pressure against
atmosphere, those with measuring spans ≥ 160 bar the inlet pressure against vacuum.
Description
4.4 Functional principle
SITRANS P320/P420 (mA/HART)
Operating Instructions, 06/2018, A5E44852162-AA 31