Quadra 4 Operator Manual
Tomtec
173
It may be necessary to use trial and error to determine the best position. You should
count turns clockwise or counter-clockwise from your starting point to know where you
are. In general terms, if the plate to be released is still hanging in the cassette, it probably
means the escapement closed too quickly and pinched the plate before it cleared. In this
case, turn the sensor clockwise to cause it to go down, holding the escapement open
longer. If two plates were released, instead of one, then the opposite is true. Turn the
adjusting screw counter-clockwise to cause the sensor to move up.
The top sensor, mounted on the stacker cylinder PC Board, tells the logic system that
the air cylinder has completed its upward stroke. This initiates the escapement opening
sequence. After a software time delay, the stacker air cylinder up solenoid valve closes
and vents the up motion, allowing the air pressure to drive the stacker cylinder down. The
flag actuates the bottom sensor to indicate the stacker is down and the system is ready
for the next motion. If the bottom sensor is not actuated, the logic system assumes the
stacker is up and will not move the shuttle. An error signal is generated at that time.
8.0 Quadra Stage
The stage lifts the plate nests from the Quadra 4 shuttle to the tips. Four pins on the top of
the stage locate into the corresponding holes on the bottom of the nests. This permits the
precision necessary for 384 and 1536 operation. The stage height is set in the program. It
also has the ability to index in both the X and y direction. This indexing allows formatting
from 96 to 384 or 1536. Since it provides full motion, it also permits serial dilution testing
when used with the 450µL head.
To reformat, the stage must rise above the shuttle to clear it. It also must be below the tips
to clear them. This distance is referred to as the safe height. The stage must rise to this
safe height before it can offset.
The X-motion of the stage is your left and right when you are facing the Quadra 4. The Y-
motion is front to back. The software will automatically set the coordinates for the required
offset for the quadrants of the 384 or the 1536 plate. However, you may wish to modify
these for a particular plate or application. Use quadrant #1 of the 384 well plate as an
example. The mathematical offset to quadrant # 1 calculates to be 144 X and 144 Y. To
move the plate to the right, causing the tips to be closer to the left side of the well, enter a
negative number for X. To have the plate move forward, causing the tips to move toward
the back wall of the well, enter a negative number for Y. The numbers you are entering are
actual stepper motor steps. Each step will move the stage 0.0006125 inches.
For Serial Dilution testing, the stage moves approximately half way in both directions (except
Q4 LTD and Q4 SPE). Assume a full plate dilution is to be made in the twelve tip direction.
A single row, of twelve tips, is loaded in Row D. The stage shifts half way forward so the
single row of tips starts at Row A. Then indexes to the rear so that they end up in Row H.
The Quadra 4 stage has a built in safety feature. It is spring loaded. Should it meet an
obstacle with more resistance than the spring force (approximately 10-15 pounds) the
spring collapses and operates a safety switch. The stage reverses and moves down away
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