Endress+Hauser Deltapilot M FMB51 - Level Measurement in Closed Tanks with Pressure Overlay; Density Measurement

Deltapilot M FMB50/51/52/53
Endress+Hauser 7
Level measurement in closed
tanks with pressure overlay
You can determine the differential pressure in tanks with pressure overlay using two Deltapilot M. The pressure
measured values of the two probes are sent to a signal processing unit such as Endress+Hauser RMA or a PLC.
The signal processing unit or PLC determines the difference in pressure and uses this to calculate the level and
the density where necessary.
P01-FMB5xxxx-15-xx-xx-xx-005
Level measurement in a closed tank with pressure overlay
1 Probe 1 measures the total pressure (hydrostatic pressure and top pressure)
2 Probe 2 measures the top pressure
3 Signal processing unit determines the difference in pressure and uses this to calculate the level
Note!
• When selecting the Deltapilot M probes, make sure you select measuring ranges that are sufficiently wide
(→ see example).
• The process isolating diaphragm of probe 2 must not be flooded. This generates additional hydrostatic
pressure which distorts the measurement.
• The ratio of hydrostatic pressure to top pressure should be no more than 1:6.
Example:
• Max. hydrostatic pressure = 0.6 bar (9 psi)
• Max. top pressure (probe 2) = 0.3 bar (4.5 psi)
• Max. total pressure, measured with probe 1 = 0.3 bar (4..5 psi) + 0.6 bar (9 psi) = 0.9 bar (13.5 psi)
 Measuring cell to be selected: 0 to 1.2 bar (0 to 18 psi)
• Max. pressure, measured with probe 2: 0.3 bar (4.5 psi)
 Measuring cell to be selected: 0 to 0.4 bar (0 to 6 psi)
Density measurement You can measure the density in tanks with pressure overlay using two Deltapilot M and a signal processing unit
or a PLC. The signal processing unit or the PLC calculates the density from the known distance Δh between
the two probes and the two measured values p
1
and p
2
.
P01-FMB5xxxx-15-xx-xx-xx-006
Level measurement in a closed tank with pressure overlay
1 Deltapilot M determines pressure measured value p
1
2 Deltapilot M determines pressure measured value p
2
3 Signal processing unit determines the density from the two measured values p
1
and p
2
and the distance Δh
➁
➀
➂
p
2
p
1
Dh
➁
➀
➂