LW2120
Electronic level sensor
22
Reference height:
A
B
C
Fig. 15: Reference height
A:
device reference point (lower edge/sealing edge of the process connec-
tion)
B:
reference height (measuring range)
C:
zero point (tank bottom or lower end of the measuring range)
The reference height is used to define the zero point and thus the reference point for the level
measurement.
For the setting [Tank offset] = [0], the following applies
:
•
Levels below zero are not detected; [0.0 m] is provided as process value.
Tank offset:
A
B
C
D
+
Fig. 16: Tank offset
A:
device reference point (lower edge/sealing edge of the process connec-
tion)
B:
reference height (measuring range)
C:
zero point (lower end of the measuring range, tank bottom is lower)
D:
tank offset
If the zero point does not match the tank bottom, the distance between zero point and tank
bottom (D) can be entered as [Tank offset]. In the vast majority of cases, entering the reference
height will be sufficient. In some cases, however, it may be advantageous to additionally set a
tank offset. This way, the sensor knows the position of the tank bottom and may be able to
better evaluate the tank echoes.
u
Enter the distance between the zero point and the tank bottom (D) as [Tank offset].
If the tank bottom is located lower than the desired zero point, as shown in Fig. Tank offset:
u
Enter values > 0 (positive values) for the tank offset. Unless the additional setting [Negative level] =
[Permitted] is selected, the following applies:
w
False echoes within the tank offset (e.g. from agitators, heating coils, hopper or dished ends) are
suppressed.
w
Levels within the tank offset are not detected; [0.0 m] is constantly provided as process value.
If the additional setting [Negative level] = [Permitted] is selected, the following applies:
•
Negative levels (levels below the zero point) are displayed.