Self Test Mode; Self Test Menu; Display Test; Load Cell Test - CAS LP-II Service Manual

12 Self Test Mode

12.1 Self Test Menu

Once at the CAL Main menu
screen, press the 6 key. The Self
Test Menu screen will appear as
follows.

12.2 Display Test

At the Self Test Menu screen, press
the 1 key for Display Test. The
Display Test screen will show until
you press any key. It will keep
alternating the checker pattern so
that you may spot a possible
problem with a segment.

12.3 Load Cell Test

At the Self Test Menu screen, press
the 2 key for Load Cell Test. The
Load Cell Test screen will be
displayed.
Zero Adjusted: These are the raw
ADC (Analog to Digital
Converter) counts minus the
Current Zero. In the example to
the right, the Current Zero is 3569 counts.
Internal Counts: This is the raw count coming from the ADC. The Zero Adjusted and the Internal Counts
are the same except that the Zero Adjusted starts at 0 when you enter this screen. In the example
above, the Current Zero is 3569 & the Zero Adjusted is 3569 – 3569 = 0. If the Internal Counts went up to
4000, then the Zero Adjusted would be 4000 – 3569 = 431 (RAW – CURRENT ZERO = ZERO ADJUSTED).
The external weight is calculated using theses very simple values. First, the Calibrated Zero is calculated
by reading the raw counts while there is nothing on the platter. Lets say in this case that the Calibrated
Zero is 3562. The scale also stores the Span Value, which is obtained by reading the raw counts while
the full capacity is on the platter and then subtracting the Calibrated Zero. Lets say in this case that the
Span Value is 74062. This is what happens when you Span calibrate the scale. After you are done in
CAL mode, the scale saves all your changes in the EEPROM.
When we turn the scale ON, it reads the platter weight and sets the Current Zero. It makes sure that the
Current Zero is at most +5% of 60 lb from the Calibrated Zero. Let us assume that the Current Zero is
equal to the Calibrated Zero. Once the scale is ON, it simply takes the raw counts and puts it into the
following formula:
1.DISPLAY
2.LOADCELL
3.KEYBOARD
4.PRINTER
5.PEEL-OFF
< LOAD CELL TEST >
RAW
COUNTS
12369
41
< SELF TEST >
6.MEMORY SIZE
7.NV MEMORY TEST
8.SERIAL PORT
9.FIRMWARE VERSIONS
RAW
INTERNAL
0
EXTERNAL
COUNTS
0