Endress+Hauser Micropilot FMR56 - Page 82

The "Expert" menu Micropilot FMR50/FMR51/FMR52/FMR53/FMR54/FMR56/FMR57 FOUNDATION Fieldbus
82 Endress+Hauser
Compensation with external pressure measurement (PROFIBUS PA and FOUNDATION
Fieldbus)
The compensation with external pressure measurement is only available for devices
with PROFIBUS PA or FOUNDATION Fieldbus.
In many cases the dielectric constant is proportional to the pressure of the gas phase. If the
proprotionality factor is known, a gas phase compensation can be performed by measuring
the pressure externally.
The device receives the externally measured pressure p of the gas phase through one of
the Analog Input Blocks and uses the user defined gas phase compensation factor F to
calculate the dielectric constant ε of the gas phase according to the following formula:
ε = 1 + Fp
ε is then used to calculate the correction of the measured distances.
2
ENDRESS + HAUSER
P
P
1
4
2
3
A0016304
 10 Gas phase compensation with external pressure measurement
1 Levelflex
2 Segment coupler
3 PLC
4 Absolute pressure transmitter
Parameter Meaning Parameter
description
GPC mode Select the External correction option. (→  83)
External pressure selector Select the AO block through which the externally
measured pressure is received.
(→  83)
External pressure Displays the pressure read in from the AO block (→  84)
Gas phase compensation factor Enter the factor F. (→  84)
Suitable value of the gas phase compensation factor for saturated steam in the
temperature range 100 to 350 °C (212 to 662 °F):
F = 0.00505 / bar