Endress+Hauser Deltapilot M FMB51 - Measuring Principle

Deltapilot M FMB50/51/52/53
6 Endress+Hauser
Measuring principle
P01-FMB5xxxx-15-xx-xx-xx-004
Deltapilot M hydrostatic level measurement and measuring principle
1 Rear isolating membrane of the CONTITE™ measuring cell
2 Measuring element
3 Process isolating diaphragm
g Gravitational acceleration
h Level height
p
ges
Total pressure = hydrostatic pressure + atmospheric pressure
p
atm
Atmospheric pressure
p
hydr.
Hydrostatic pressure
p
mess
Measured pressure in the measuring cell = hydrostatic pressure
ρ Density of the medium
Due to its weight, a liquid column creates hydrostatic pressure. If the density is constant, the hydrostatic
pressure depends solely on the height h of the liquid column.
The CONTITE™ measuring cell, which works on the principle of the gauge pressure sensor, constitutes the
core of Deltapilot M. In contrast to conventional gauge pressure sensors, the precision measuring element (2)
in the CONTITE™ measuring cell is absolutely protected, situated between the process isolating diaphragm
(3) and the rear isolating membrane (1). Thanks to this hermetic sealing of the measuring element, the
CONTITE™ measuring cell is absolutely insensitive to condensate/condensation and aggressive gases. The
pressure applied is transferred from the process isolating diaphragm to the measuring element by means of an
oil without any loss in pressure.
Two temperature sensors, which measure the distribution of temperature in the cell, are arranged between the
process isolating diaphragm and measuring element. The electronics can compensate any measuring errors
resulting from fluctuations in temperature with these measured temperature values.
A linearization function with max. 32 points, based on a table entered either manually or semi-automatically,
can be activated locally or remotely. This function facilitates
measurement in engineering units, and provides a linear output signal for spherical and horizontal cylindrical
tanks, and vessels with a conical outlet.
h
h =
p
r · g
hp
p
atm
hydr.
p
p
atm
p
atm
ges
p
hydr.
p
+
p
atm
=
ges
p
)
hydr.
p
+
(p
atm
p
atm
p
mess
=
–
p
ges
p
atm
p
mess
=
–
p
ges
p
atm
p
mess
=
–
1
2
3