Commissioning | Radar Tank Gauge |
Dip table
The dip table is used to correct the level readings of the 7500 RTG using independently taken hand dips. The dip table is used in particular to adapt the level gauge to the specific application conditions as mechanical offset and tank/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 7500 RTG accepts the corrected measured values identically for both value pairs. All other measured values are determined by linear extrapolation.
If you enter more than two value pairs, the system carries out a linear interpolation between adjacent value pairs. Outside these value pairs, extrapolation is also linear.
basic setup
history reset
dip table
alternatives
preferred choice:
hand dip and
immediate
offset correction in
semi-automatic mode
collect further hand dip data; if deviation from measurements
>4 mm and level change > 2 m: enter a new dip value into dip table using the
collect hand dip and
measurement data over full measurement range
evaluate collected data; enter characteristic value pairs into the dip table using the manual mode
Figure 8: Alternative procedures to fill the dip table.
To collect and enter data into the dip table, two alternative procedures may be carried out. In order not to mix up measurement values corrected by the offset or linearization of the dip table with uncorrected measurement values, it is recommended to use the
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 Figure 8:, right side). If further linearization is needed, further hand dip values should be entered using only the
Note!
The offset should NOT be determined and entered within the close range of the antenna (conf. definition of the safety distance) or immediately in the range of the tank bottom, because within these ranges interferences of the radar signal may occur.
60 | Installation and Operations Manual |
