Siemens SITRANS LG250 Operating Instructions Manual page 10

Functional principle - in-
terface measurement
10
h
Fig. 2: Level measurement
1 Sensor reference plane (seal surface of the process fitting)
d Distance to the level
h Height - Level
High frequency microwave impulses are guided along a steel cable or
rod. Upon reaching the product surface, a part of the microwave im-
pulses is reflected. The other part passes through the upper product
and is reflected by the interface. The running times to the two product
layers are processed by the instrument.
h2
h1
Fig. 3: Interface measurement
1 Sensor reference plane (seal surface of the process fitting)
d1 Distance to the interface
d2 Distance to the level
TS Thickness of the upper medium (d1 - d2)
h1 Height - Interface
h2 Height - Level
L1 Lower medium
L2 Upper medium
L3 Gas phase
SITRANS LG250 - Operating Instructions
d2
L3
L2
TS
L1
1
d
1
d1
PBD-51041053