Parameter reference
SITRANS LR250 with FOUNDATION FIELDBUS
Operating Instructions, 09/2021, A5E32221411-AH
131
Near Range (2.5.1.)
The range in front of the device (measured from the sensor reference point within which any
echoes will be ignored. (This is sometimes referred to as "Blanking" or "Dead Zone".) The
factory setting is 50 mm (2") past the end of the antenna, and the range is dependent on the
antenna type and process connection. [See Threaded Horn Antenna with extension
(Page 191) and Flanged Horn (Page 196) for antenna heights to sensor reference point.]
Values
Range:
0
to
20
m (0 to 65.6 ft)
Default depends on antenna type and process connection.
Examples:
1.5" threaded horn
185.3 mm (7.3")
4" horn with stainless steel flange
and 100 mm (4") extension
373.3 mm (14.7")
Related parame-
ters
Unit (2.2.1.)
Far Range (2.5.2.)
Note
Far Range can extend beyond the bottom of the vessel.
Allows the material level to drop below Low Calibration Point without generating a Loss of
Echo (LOE) state. See
Low Calibration Pt. (2.3.7.1.)
for an illustration.
Values
Range: Min. =
Low Calibration Pt.
Max. =
33
m (108.27 ft)
Default: Value for Low Calibration Pt. + 1 m (3.28 ft)
Related parameters
Unit (2.3.1.)
CLEF (Constrained Leading Edge Fit) Range (2.5.7.4.)
a)
a)
The value set for Far Range becomes the CLEF Range maximum. If the value for Far Range is
changed after a CLEF Range value is entered, CLEF Range is reset to its default (0.00 m).
Use this feature if the measured surface can drop below the Low calibration point in normal
operation.
Propogation Factor (2.5.3.)
Note
•
When operating in a stillpipe, values for
CLEF Range (2.5.7.4.)
, and for the Propagation
Factor, should be set according to the pipe size. See the table below.
•
For reliable results the antenna size must be close to the pipe size.
Compensates for the change in microwave velocity due to propagation within a metal
stillpipe instead of in free space.
Values
Range:
0.3
to
1.0
depending on pipe size.
Default:
1.0000