Endress+Hauser Levelflex FMP53 Operating Instructions Manual page 25

Levelflex FMP53 PROFIBUS PA
Endress+Hauser
Plastic and glass vessels: Mounting the probe on the outside wall
In the case of plastic and glass vessels, the probe can also be mounted on the outside wall
under certain conditions.
1 Plastic or glass vessel
2 Metal plate with screw-in sleeve
3 No space between vessel wall and probe!
Requirements
• Dielectric constant of the medium: ε
• Non-conductive vessel wall.
• Maximum wall thickness (a):
• Plastic: < 15 mm (0.6 in)
• Glass: < 10 mm (0.4 in)
• No metal reinforcements on the vessel.
Note the following when mounting the device:
• Mount the probe directly on the vessel wall without any space between the wall and
probe.
• To prevent any influence on the measurement, fit a plastic half pipe with a diameter of
at least 200 mm (8 in), or a similar protective unit, on the probe.
• For vessel diameters less than 300 mm (12 in):
On the opposite side of the vessel, fit a grounding plate that is conductively connected to
the process connection and covers around half of the vessel' s circumference.
• For vessel diameters of 300 mm (12 in) and higher:
At the process connection, fit a metal plate with a diameter of at least 200 mm (8 in) at
a right angle to the probe (see above).
Adjustment when mounting on the vessel exterior
When the probe is mounted on the outside of the vessel wall, the speed of propagation of
the signal is reduced. There are two ways to compensate for this.
Compensation via gas phase compensation factor
The effect of the dielectric wall is comparable to the effect of a dielectric gas phase and can
therefore be corrected in the same way. The correction factor is calculated as the quotient
of the actual probe length LN and the probe length measured when the vessel is empty.
The device determines the position of the probe end echo in the differential curve.
Therefore, the value of the measured probe length depends on the mapping curve. In
order to obtain a more accurate value, it is advisable to determine the measured probe
length manually using the envelope curve display in FieldCare.
1. Parameter Expert → Sensor → Gas phase compensation → GPC mode
 Select the Const. GPC factor option.
2
1
a
> 7.
r
3
Mounting
A0014150
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