STX Signal Transmitter Installation and Operation ... - Kistler-Morse

Chapter 7. MVS-STX Calibration Menu
High-Accuracy Calibration
This procedure provides the highest accuracy,
but requires that the vessel be completely
empty to start. The principle behind the
calibration follows.
The vessel is completely emptied, and the
Lo Span weight is set to zero [point (1) in
Figure 7-2]. A known quantity of material,
representing at least 25% of the vessel’s total
capacity, is then added to the vessel. That
quantity is entered as the Hi Span weight
[point (2) in Figure 7-2]. The MVS saves in
memory the Lo Span and Hi Span weights as
well as the digital counts associated with
each weight. These values define the straight
line shown in Figure 7-2. The slope of the line
is called the Scale Factor, which is calculated
internally.
The accuracy of the calibration improves the
greater the known quantity of material added
during the calibration procedure. For
example, adding 50% of the vessel’s total
capacity results in greater accuracy than
adding 25% of the total capacity.
Follow this procedure to perform a highaccuracy
calibration:
1. Completely empty the vessel.
2. If in Auto Mode (Auto LED illuminated),
press the Auto/Man Key to put the MVS
in Manual Mode. The Auto LED turns off.
3. Use the Arrow Keys to scroll to the
desired channel.
4. Press the Menu Key to display the Main
Menu. The display shows:
MAIN MENU
Disp I/O Cal
F1 F2 F3
5. Press the F3 Key to access the Cal
Menu. The display shows:
CALIBRATION MENU
6. Press the F1 Key to access the Auto
Menu. The display shows:
AUTO CAL MENU
7. Press the F1 Key to access LoSpan. The
display looks like this:
LO SPAN AUTO CAL
(Units are consistent with Units Menu.)
8. Use the keypad or Arrow Keys to input
zero as the LoSpan. Press the Enter
Key. The display acknowledges the entry
and returns to:
AUTO CAL MENU
Note
Auto
Manual
F1 F2 F3
LoSpan
HiSpan
F1 F2 F3
> 0 lbs
F1 F2 F3
LoSpan
HiSpan
F1 F2 F3
If the filling process takes a long time
and you need to use the MVS to
monitor vessel contents during filling,
enter ScfCnt, ScfWgt, and then
Zero_Cal now. (If you do not,
disregard channel monitoring data until
you complete the Auto Calibration in
Steps 9 through 11.) Complete the
Auto calibration as described below.
9. Add a known quantity of material,
representing at least 25% of the vessel’s
total capacity, to the vessel.
Indicated
Weight
Hi Span
Weight
Added
Known
Quantity
(2)
Scale Factor Weight
Slope =
Scale Factor Counts
Scale Factor Wt = Hi Span Wt - Lo Span Wt
Scale Factor Cnts = Hi Span Cnts - Lo Span Cnts
Lo Span
Weight (Zero)
(1)
Lo Span
Counts
Hi Span
Counts
Figure 7-2. High-Accuracy Calibration
Weight
Signal
in Counts
7-2