Kistler-Morse KM Weigh II - Manual (Page 43)

Chapter 6. Calibration
6-5
Known Quantity of Material
This method provides calibration that is
accurate enough for most applications, and
does not require the vessel to be empty. This
method of calibration is appropriate when it is
easier to remove material from the vessel
than to add it. The principle behind the
calibration follows.
A value estimated to be the quantity of
material in the vessel is entered as the Hi
Span value [point (2) in Figure 6-3]. A known
quantity of material, representing at least
25% of the vessel’s total capacity, is removed
from the vessel. The estimated Hi Span value
minus the known quantity that is removed is
entered as the Lo Span value [point (1) in
Figure 6-3]. The Weigh II saves in memory
the Lo and Hi Span weights as well as the
digital counts associated with each weight.
These values define the dashed straight line
and the calculated zero weight shown in
Figure 6-3. The slope of the line is called the
Scale Factor, which is calculated internally.
The slope of the line is reasonably accurate,
because it is calculated based on the known
difference between the Lo Span and Hi Span
weights and counts. However, if the estimated
Hi Span value is incorrect, the actual “loca-
tion” of the line is incorrect, resulting in errors
in vessel monitoring. The greater the error in
the estimated Hi Span, the greater the
resulting error. The “location” of the line can
be adjusted to the solid line by manually
setting zero [point (3) in Figure 6-3].
Similarly to the other calibration methods, the
greater the known quantity of material moved
during the calibration procedure, the greater
the accuracy. Removing 50% of the total
capacity results in greater accuracy than
removing 25% of the total capacity.
Follow this procedure to calibrate by subtract-
ing a known quantity of material.
1. If the Weigh II is in Auto Mode (Auto LED
illuminated), press the Auto/Man Key to
put the system in Manual Mode. The Auto
LED turns off.
2. Use the Up Arrow or Down Arrow Keys to
scroll to the desired vessel.
3. Press the Menu Key to display the Main
Menu. The display shows:
4. Press the F3 Key to access the Cal Menu.
The display shows:
5. Press the F1 Key to access the Auto
Menu. The display shows:
6. Press the F3 Key to access HiSpan. The
display looks like this:
The unit of measure you set up in the
Units Menu shows in place of lbs.
7. Use the keypad or the Up and Down Arrow
Keys to input a value that represents the
estimated quantity of material in the vessel
as the HiSpan value. Press the Enter Key
to save the value in memory. Hi Span is
now set [point (2) in Figure 6-3]. The
display flashes a message acknowledging
your entry and returns to:
8. Remove a known quantity of material, that
represents at least 25% of the vessel’s
total capacity, from the vessel.
9. Press the F1 Key to access LoSpan. The
display looks like this:
The unit of measure you set up in the
Units Menu shows in place of lbs.
CALIBRATION MENU
Auto Manual
F1 F2 F3
AUTO CAL MENU
LoSpan HiSpan
F1 F2 F3
WII MAIN MENU
Disp I/O Cal
F1 F2 F3
HI SPAN AUTO CAL
> X lbs
F1 F2 F3
LO SPAN AUTO CAL
> X lbs
F1 F2 F3
AUTO CAL MENU
LoSpan HiSpan
F1 F2 F3