Deltabar S PMD70/75 FMD76/77/78

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Deltabar S
Pressure on the negative side of the differential pressure transmitter (p – ) when the tank is empty (min. level)
p – = p + p = Hv • ρ • g + H1 • ρ • g + p
Hv H1
Fl Fl i
kg
= 1.8 m • 0.96 • 9.81
m kg
+ 0.3 m • 0.96 • 9.81
m
+ p
dm 3 s dm 3 s i
= 197.77 mbar + pi
Pressure on the positive side of the differential pressure transmitter (p + ) when the tank is empty (min. level)
p
+
= p + p = Hu • ρ • g + H1 • ρ • g + p
Hu H1 M
Fl i
kg
= 0.2 m • 1 • 9.81
m kg
+ 0.3 m • 0.96 • 9.81
m
+ p
dm 3 s dm 3 s i
= 47.87 mbar + pi
Differential pressure at the transmitter (p Transmitter ) when the tank is empty
Result:
If the tank were full, a differential pressure of –51.80 mbar (-0.762 psi) would be present at the differential pressure
transmitter. When the tank is empty, a differential pressure of –149.90 mbar (2.2485 psi) is present. Therefore, a 500 mbar
(7.5 psi) measuring cell is required for this application.
Capillary
In order to obtain more precise measurement results and to avoid a defect in the device, mount the capillaries
as follows:
• vibration-free (in order to avoid additional pressure fluctuations)
• not in the vicinity of heating or cooling lines
• insulate if the ambient temperature is below or above the reference temperature
• with a bending radius of 100 mm (3.94 in).
66 Endress+Hauser
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