Endress+Hauser Deltabar S FMD 77 - Measuring Principle

Deltabar S
6 Endress+Hauser
Measuring principle
Ceramic measuring diaphragms used for PMD 70 and FMD 76
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 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 0.02 psi
abs
(1 mbar
abs
)
• Metal-free versions available
• Secondary process barrier for enhanced mechanical integrity
Metallic measuring diaphragms used for PMD 75, FMD 77 and FMD 78
The separating 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 change due to differential pressure
of the bridge output voltage is measured and further processed.
Advantages:
• Standard operating pressures: 2320 psi and 6100 psi (160 bar and 420 bar)
• High long-term stability
• Very high single-sided overload resistance
• Secondary process barrier for enhanced mechanical integrity
Ceramic measuring diaphragms used for PMD 70
and FMD 76
Metallic measuring diaphragms used for PMD 75, FMD 77 and FMD 78
P01-xMD7xxxx-03-xx-xx-xx-000
Ceramic measuring cell PMD 70 and FMD 76
1 Meter body
2Diaphragm
3 Electrodes
4 Glass frit fixes the diaphragm onto the meter
body
5 Temperature sensor
P01-xMD7xxxx-03-xx-xx-xx-002
Metal measuring cell 4 inH
2
O (10 mbar) and
12 inH
2
O (30 mbar)
1 Sensing element
2 Silicon diaphragm
3 Separating diaphragm
4 Filling oil
5 Integrated overload protection
P01-xMD7xxxx-03-xx-xx-xx-003
Metal measuring cell for 40 inH
2
O (100 mbar) and
above
6 Sensing element
7 Overload diaphragm/Middle diaphragm
8 Filling oil
9 Separating diaphragm
1
p
2
p
1
2
3
4
5
1
p
2
p
1
2
3
4
5
1
p
2
p
6
7
8
9