Description
3.6 Principle of operation
SITRANS P DS III with PROFIBUS PA
Operating Instructions, 06/2013, A5E00053276-07
29
● Flange connection in accordance with EN 61518
● Flush-mounted process connections
Measuring cell for gauge pressure
Reference pressure opening
Figure 3-7 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.
Transmitters with measuring span ≤ 63 bar measure the inlet pressure against atmosphere,
those with measuring spans ≥ 160 bar against vacuum.
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