User's Manual

BD =
new
a
1-
e
2
scale
x 1-
b
BD
2
orig
Commissioning
Page 34
Figure 3.12 Sign of scale error
3.4.9 Additional adjustment with measurement on stilling well
The propagation speed of the microwave, and hence the level measurement, depends on the inner diameter
of the stilling well. The smaller the diameter, the lower the propagation speed, resulting in a larger measured
radar ullage.
Item
BD
holds the inner diameter of the stilling well. When the real value of the inner diameter differs from
the setting in item
BD
, the SmartRadar has a ‘gain’ error in the level measurement.
It is therefore recommended to check the level reading of the SmartRadar LT with some manual dips at
different static levels over the full operating range.
Note:
After commissioning, the AdvancedDSP routines require one complete passage through the full
operating level range, before the optimum accurate level reading is obtained.
A level gain error, when present, can be corrected in two ways:
• ullage correction table
• adjustment of item
BD
For the correction via the ullage correction table, refer to the description of items
CW
,
CL
and
CS
.
The correct value for the stilling well diameter can be calculated with the following equation:
where:
Antenna type
ab
S06, S08, S10, S12 0.036568 0.0013372
H04, H02 0.017568 0.0003086
BD : recalculated stilling well diameter [m]
new
BD : original stilling well diameter [m]
orig
ε : scale error (relative gain error)
scale
example: 10 mm gain error on 20 m range: ε = 20 / (20 + 0.010) = 0.9995.
scale
for the sign of the scale error, refer to figure 3.12. If α is positive, the scale error
sign is positive; if a is negative, the scale error sign is negative.