Siemens SITRANS LR250 Operating Instructions Manual page 111

2.5.1. Near Range
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 past the end of the horn,
and the range is dependent on the horn type.
Values
Related
parameters
2.5.2. Far Range
Note:
Allows the material level to drop below Low Calibration Point without
generating a Loss of Echo (LOE) state. See Low Calibration Point (2.3.7.1.) on
page 99 for an illustration.
Values
Related
Parameters
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 Cal. Point in
normal operation.
2.5.3. Propagation Factor
Notes:
• When operating in a stillpipe, values for CLEF (Constrained Leading Edge
Fit) 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 horn 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
1)
See Flat Faced Flange on page 16 and Threaded Horn Antenna with extension on
page 12.
7ML19985KL01
Range: 0 to 33 m (0 to 108.27 ft)
Default depends on antenna.
Examples:
1.5" horn, Default = 0.185 m (7.28")
4" horn, Default = 0.270 m (10.62")
Unit (2.3. 1 .)
Far Range can extend beyond the bottom of the vessel.
Range: min. = Low Calibration Point
max. = 33 m (108.27 ft)
Default: Low Calibration Point + 1 m (3.28 ft)
Unit (2.3.1.)
CLEF (Constrained Leading Edge Fit) Range (2.5.7.4.)
Range: 0.3 to 1.5 depending on pipe size.
Default: 1.000
SITRANS LR250 (FF) – OPERATING INSTRUCTIONS
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Page 105