Micropilot NMR84
Operating menu
Hauser
205
"Dip-table" submenu
Dip table
The dip table is used to correct the level readings using independently taken hand dips.
The dip table is used in particular to adapt the level gauge to the specific application
conditions such as a mechanical offset and the tank or stilling well design. Depending on
national regulations, national inspectors will dip the tank at one to three levels during a
calibration run and check the level readings.
Only one value pair must be entered into the dip table to correct the measurement offset.
If a second value pair is entered into the dip table, the device accepts the corrected
measured values identically for both value pairs. All other measured values are determined
by linear extrapolation.
If more than two value pairs are entered, the system carries out a linear interpolation
between adjacent value pairs. Outside these value pairs, extrapolation is also linear.
• The offset should
not
be determined and entered within the close range of the
antenna or immediately in the range of the tank bottom, because within these
ranges interferences of the radar signal may occur.
• The entries of the dip table must be arranged in an ascending order of levels. If table
values have not been entered in the correct order, they can automatically be
rearranged by selecting
Sort table
• After changing the
Empty
Table mode
parameter
(→ 208) is automatically set to
Disable
.
• If
has been changed by more than 20 mm (0.8 in), it is
recommended to delete the dip table.
• The dip table values are not affected by a change of the
Empty
parameter
Semiautomatic creation of a dip table
In order not to mix up measurement values corrected by the dip table with uncorrected
measurement values, it is recommended to enter new data pairs semiautomatically into
the table. This means: the uncorrected level is measured by the device and the user only
enters the corresponding dip value.
The first dip value should be entered immediately after the basic calibration. Further dip
points should be entered only after a level change of at least 2 m (6.6 ft) and a deviation
between the uncorrected measurement value and the hand dip value of at least
4 mm (0.16 in).
If this procedure can not be followed, then
no
value pair should be entered into the dip
table after basic calibration. Measurement data and hand dip values should be collected
over the full measurement range and be evaluated with regard to a good linear fit. Only
then characteristic value pairs should be entered into the dip table using the "manual
mode" (see below).
Manual creation of a dip table
Before creating a dip table manually, measured levels and dip values should be collected
over the full measurement range and be evaluated with regard to a linear fit. Only then
characteristic value pairs from this fit should be entered into the dip table using the
manual mode. In the manual mode both, the measured level (without correction) and the
corresponding dip value are entered by the user.
If further linearisation is needed, further hand dip values should be entered using only
the "semi-automatic" mode (see above).
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