Bio-Rad Components for Older Model Spot Cutter - Manual (Page 17)

7. There are two parameters to adjust in the calibration for both x and y dimensions. The
OFFSET is the distance the image area is from the 0,0 position for the system's x,y axis.
Adjusting x and y offset moves the whole cutting area. This is defined in linear terms
with 100 offset units equal to 1 mm on the cutting platform.
PPX and PPY are adjustments to the distance between two points in the cutting area. If
the corners of the plate are too close or too far apart from each other to match the
calibration template, the ppx or ppy is adjusted accordingly. The digits in the ppx and
ppy do not relate to a linear dimension. Large movements of adjustment should be made
with changes to the digits in the 3rd place (0.00X). Fine adjustments are generally made
in the 4th place (0.000X). The process will require adjustments of the number value, and
then checking for the result by a single "cut" without cutting the template.
The following diagram is an example for explanation purposes of the calibration routine.
"Circles" are the positions that are selected on the SpotOn screen. Square spots show the
position that the spot is actually "cut". The square spots are adjusted during calibration to
"cut" the circles.
Circles indicate where the spot should be cut
Squares indicate the spot that is actually cut.
• The squares need to be adjusted to the same position as the circles in the examples.
Y Pixel and Offset Calibration (Y Offset and PPY)
1. Select spot #1 (see diagram), and select to next MTP Well.
2. Hint: Take note of where the 1st spot "y pixel" coordinate is on the monitor. This can be
used to line up the 2nd spot y coordinate
Hint: To get a more accurately cut spot, click on the Enable Arrow Keys shortcut button
on the shortcut menu bar and use the arrow keys for fine cursor control.
3. Select spot #2 (see diagram).
4. Run the cutting run for spots #1 and 2.
Hint: Stop the cutting tip down on the calibration plate by clicking on any menu item as the
tip comes down. (Do not select any of the options.) This will freeze the system and will
provide a longer time to evaluate the location of the cutting tip.
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