Deltabar S
Endress+Hauser 5
Measuring principle
Ceramic process isolating diaphragm used for PMD70 and FMD76
The ceramic measuring cell is based on the principle of a plate capacitor with an electrode on a meter body (1)
and a movable electrode on the interior of the diaphragm (3). Silicone oil or mineral oil are used as the standard
filling oils for this measuring cell.
A differential pressure (p
1
zp
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
(0.015 psi)
• Metal-free versions available
• Secondary containment for enhanced integrity
Metal process isolating diaphragm 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 bridge (semi-conductor technology). The change in the bridge output
voltage, which depends on the differential pressure, is measured and processed further.
Advantages:
• Standard system pressures: 160 bar (2400 psi) and 420 bar (6300 psi)
• High long-term stability
• Very high single-sided overload resistance
Specialties
(options)
– Metal-free
measurement with
PVDF flange
– Available with
Deltatop as flow
compact device
–p
stat
to 420 bar
(6300 psi)
– Process isolating
diaphragm: tantalum
– Available with
Deltatop as flow
compact device
– Abrasion-resistant and
corrosion-resistant
– No diaphragm-seal
temperature effects
– Metal-free
measurement possible
with ECTFE-coated
process connection
–For high media
temperatures
– Wide range of
diaphragm seals
–HistoROM
®
/M-DAT memory module
1) OPL: over pressure limit; dependent on the lowest-rated element, with regard to pressure, of the selected components
2) Lower temperatures on request
Deltabar S –
product family
PMD70 PMD75 FMD76 FMD77 FMD78
Ceramic process isolating diaphragm used for
PMD70 and FMD76
Metal process isolating diaphragm used for PMD75,
FMD77 and FMD78
P01-xMD7xxxx-03-xx-xx-xx-000
1 Meter body
2 Process isolating diaphragm
3Electrodes
4 Glass frit fixes the process isolating diaphragm
onto the meter body
5Temperature sensor
P01-xMD7xxxx-03-xx-xx-xx-003
6 Sensing element
7 Middle diaphragm
8 Filling oil
9 Process isolating diaphragm
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