User manual

Model: 2100 &2300 Series
2100UM22.DOC Rev: 2.2
- 19 -
4.2 CALIBRATION [CALIB]
The unit may be calibrated 3 different ways: Automatic Calibration and 2 Manual Calibrations.
Pressing the CALIBRATION key enters the CALIBRATION menu:
*** CALIBRATION ****
1-Auto 2-Manual
3-Slope/Off 4-FS val
4.2.1 AUTOMATIC CALIBRATION [CALIB\1]
This is typically done for a new installation. It involves entering the independently and
ACCURATELY MEASURED level in the vessel, changing the level by some amount, then
entering the new ACCURATELY MEASURED level. The unit then calculates 2 parameters:
SLOPE and OFFSET by correlating the 2 entered percentage levels with the corresponding
measured capacitance. The SLOPE is the change in capacitance in pF per percent change in
level. The OFFSET is the calculated empty vessel capacitance in pF. The Automatic Calibration
procedure is already described in Section 3.4.5.
NOTE: The accuracy of the calibration depends in large part on the accuracy of the 2 measured
levels entered during calibration. The resolution of measurement should be 2 decimal places to
get the best accuracy. This is also why a minimum of 10% change in level is recommended for
the 2 calibration points, since the larger the difference, the less affect the inaccuracies of entered
levels has on the calibration. For example, a 1% error in entered values over a 10% change
translates to a 10% error at Full Scale (100%).
NOTE: if the SLOPE and OFFSET parameters are already known, they may be entered directly
by selecting SLOPE/OFF (item 3 from the Cal menu). This can save a lot of time. Also, FOR
CONCENTRICALLY SHIELDED PROBES, THE SLOPE AND OFFSET ARE INDEPENDENT OF
THE VESSEL GEOMETRY AND FOR A GIVEN MATERIAL IN THE VESSEL, THE SLOPE AND
OFFSET MAY BE FACTORY DETERMINED, THUS SAVING CALIBRATION TIME ONSITE.
4.2.2 MANUAL CALIBRATION [CALIB\2]
This option is used to fine-tune the SLOPE and OFFSET values after a successful Automatic
Calibration or when the capacitance at 2 differing percent levels is known. For example if the
capacitance and corresponding levels in % have been recorded over some time then these can
be used to recalibrate the unit by using two levels which are furthest apart (and their
corresponding capacitance values). The procedure is as follows:
At any time, to view the measured capacitance:
 Press the SETUP key then 2 for Diags:
 Read the capacitance in pF on the 2
nd
line from the top.
 Determine the actual level in percent in the vessel: (2 places of decimal accuracy)
 The above steps must be repeated for one other level, which is different from the first by at
least 10%.
TO CALIBRATE USING MANUAL CALIBRATION:
 Press the CALIBRATION key to get to the CALIBRATION menu then 2 for Manual.
 Enter the 1st level in percent (2 decimal places) then press the Enter key.
 Enter the 1st (corresponding) capacitance
 The unit then prompts for the 2nd level in percent and the 2nd capacitance. After entering
these values the unit will calculate the SLOPE and OFFSET. Use the Slope/Off menu item
described below to view and record these values for future reference.