Dielectric Constant; End Of Probe Evaluation - Endress+Hauser Levelflex M FMP41C Technical Information

Dielectric constant

End of Probe evaluation

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FMP41C
Rod probe, Cable probe PFA (Daikin PFA AP230)
Cladding PTFE (Dyneon TFM1600)
FMP45
Process connection Stainless steel 1.4435/316L
Probe Stainless steel 1.4435/316L
FMP41C
ε
r ≥ 1.6
• Rod and cable probe:
• When installing in metallic pipes ≤ 6" (DN ≤ 150 mm):
FMP 45
ε
r ≥ 1.6, when installing in pipes ≤ 6" (DN ≤ 150 mm):
• Rod and cable probe:
ε
r ≥ 1.4
• Coax probes:
The Levelflex can measure the level of a material with a very low dielectric constant by using two redundant
methods: the surface reflection and the evaluation of the "End of Probe" shift.
An electromagnetic wave traveling through a material with a dielectric constant higher than 1 will slow down.
Therefore, the reflection of the probe end is delayed compared to the probe end reflection of a material-free
probe. This time shift is dependent on the material level and the dielectric constant of that specific material
under process conditions. When a reflection of the surface is detected, the level is derived from this signal. In
addition, the specific dielectric constant of a product under process conditions can be determined combining
the level and the time shift of the End of Probe signal.
In case the surface reflection is too weak, the level is derived from the shift of the "End of Probe" signal, using
the last calculated dielectric constant of the material. This mode will operate until a signal from the surface is
detected again and the dielectric constant of the material can be updated.
Material
Rod and coax probe
Stainless steel 1.4435/316L
Alloy C22
ceramic Al O , 99.7%
2 3
pure graphite
ε
r ≥ 1.4
Levelflex M FMP41C, FMP45
Approval
FDA, 3-A
FDA, 3-A
Cable probe
Alloy C22
ceramic Al O , 99.7%
2 3
pure graphite
Stainless steel 1.4401/316
ε
r ≥ 1.4
Level
D
t
Endress+Hauser