Deltabar S
Endress+Hauser 5
Measuring principle
Ceramic process isolating diaphragms used for PMD70 and FMD76
The ceramic measuring cell is based on the principle of a plate capacitor with an electrode on (1) and a movable
electrode on the interior of the diaphragm (3). Standard silicone oil or mineral oil filling oils for this measuring
cell.
A differential pressure (p
1
p
2
) causes a corresponding deflection of both diaphragms. Both capacitance values
are converted and are fed to the microprocessor of the transmitter as a digital signal.
Advantages:
• Self-monitoring for process isolating diaphragm break or oil loss (constant comparison of the measured
temperature with a temperature calculated from the capacitance values)
• Extremely high resistance to aggressive media
• Suitable for vacuums up to 1 mbar
abs
• Metal-free versions available
• Second process barrier (Secondary Containment) for enhanced integrity
Metallic process isolating diaphragms used for PMD75, FMD77 and FMD78
The process isolating diaphragms (3/9) are deflected on both sides by the acting pressures. A filling oil (4/8)
transfers the pressure to a resistance circuit bridge (semi-conductor technology). The differential-pressure-
dependent change of the bridge output voltage is measured and further processed.
Advantages:
• Standard operating pressures: 160 bar and 420 bar
• High long-term stability
• Very high single-sided overload resistance
• Second process barrier (Secondary Containment) for enhanced integrity
Ceramic process isolating diaphragms used for
PMD70 and FMD76
Metallic process isolating diaphragms used for PMD75, FMD77 and FMD78
P01-xMD7xxxx-03-xx-xx-xx-000
Ceramic measuring cell PMD70 and FMD76
1 Meter body
2 Process isolating diaphragm
3 Electrodes
4 Glass frit fixes the process isolating
diaphragm onto the meter body
5 Temperature sensor
P01-xMD7xxxx-03-xx-xx-xx-002
Metal measuring cell 10 mbar and 30 mbar
1 Sensing element
2 Silicon diaphragm
3 Process isolating diaphragm
4 Filling oil
5 Overload diaphragm
P01-xMD7xxxx-03-xx-xx-xx-003
Metal measuring cell as of 100 mbar
6 Sensing element
7 Overload diaphragm
8 Filling oil
9 Process isolating diaphragm
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