Gemini has some pre-defined variables which allow the same script to be used for different numbers of samples or contain useful information.
11.1.3.1 CENTRIFUGE_RACK_CNT
This counter variable is incremented by the Move RoMa and RoMa Vector commands each time the RoMa places a plate into the centrifuge and is decremented each time the RoMa removes a plate from the centrifuge. It is intended for use in a sub-routine to avoid possible mechanical imbalance by always placing racks in the centrifuge in pairs.
Please note that the RoMa Vector you use to load and unload the centrifuge must be based on a carrier of type "Centrifuge". The carrier should have 4 sites (one for each centrifugation bucket). See “Centrifuge command” on page 262 for more information.
11.1.3.2 COPY_CNT
This counter variable lets you limit the number of copied source wells in Copy Plate commands. If you assign a value to COPY_CNT, Gemini will copy up to the specified number of source wells for all following Copy Plate commands. COPY_CNT is ignored if its value is larger than the number of source wells specified in the Copy Plate
command.
You cannot deactivate COPY_CNT for a part of the script, but you can assign a large number (e.g. 1000) to it, so that the well selection in the Copy Plate command is used instead.
11.1.3.3 DETECTED_VOLUME_x
The LiHa pipetting commands automatically define variables if liquid detection was used. One variable is provided for each tip on the LiHa. The detected volume is reported in µl for each tip. The variable names are as follows:
DETECTED_VOLUME_1 ...
DETECTED_VOLUME_8.
The value -1 is reported as the detected volume if the tip was used with liquid detection disabled or was not part of the pipetting command.
11.1.3.4 RACK_OFFSET
This variable lets you change the specified rack for the basic commands Aspirate, Dispense, Mix and Move LIHA. If e.g. RACK_OFFSET equals 1, Gemini searches for the next rack of the same type on the worktable. The search direction is from rear to front, left to right of the worktable. Negative values in RACK_OFFSET cause Gemini to
search in the opposite direction. You can deactivate RACK_OFFSET by setting its value to 0.
11.1.3.5 RACK_VOLUME_X
The MO does not support liquid detection. To emulate liquid detection for the Te-MO, specify the volume for the wells of the rack you are using by assigning a value to this variable. This ensures that the tips are not lowered too far into the wells of the Te-MO. Replace the X in the variable name with the rack name, e.g. use
RACK_VOLUME_SOURCE if you named the rack SOURCE. Note: For mechanical reasons, the pipetted volume for the Te-MO is the same for all wells.
11.1.3.6 REPLICATE_CNT
This counter variable lets you limit the number of pipetted destination wells in
Replicates commands. If you assign a value to REPLICATE_CNT, Gemini will pipette up to the specified number of destination wells for all following Replicates commands.
REPLICATE_CNT is ignored if its value is larger than the number of destination wells specified in the Replicates command.
You cannot deactivate REPLICATE_CNT for a part of the script, but you can assign a large number (e.g. 1000) to it, so that the well selection in the Replicates command is used instead.
11.1.3.7 SAMPLE_CNT
Gemini normally executes a script in its entire length. If you want to use a different number of samples in each run, you would need to modify the script accordingly each time you use it. The SAMPLE_CNT counter variable allows you to write a script for the maximum number of samples and to limit the script during runtime according to the actual number of samples. SAMPLE_CNT is intended for use in loops in combination with basic pipetting commands such as Aspirate, Dispense, Mix, Get DITIs and Drop DITIs.
This feature is activated by assigning a positive value to SAMPLE_CNT. If
SAMPLE_CNT is set to a value larger or equal to 0, Gemini keeps a count of how many different tips are used in each cycle of the following loop(s). The loop is then terminated the next time End Loop is executed when the number of tips used reaches
SAMPLE_CNT. If SAMPLE_CNT is not a multiple of the number of tips used in one cycle of the loop(s), Gemini modifies the tip selection in the final cycle of the loop.
The following figure shows an example of using the SAMPLE_CNT variable:
The example script copies 10 µl from the source rack to the destination rack. The loop is programmed for a maximum of 96 samples or wells. If SAMPLE_CNT is set to 13, the script is executed as follows:
• Wash tips 1-8,
• Aspirate with tips 1-8 from column 1 of the source rack,
• Dispense with tips 1-8 into column 1 of the destination rack,
• Wash tips 1-8,
• Aspirate with tip 1-5 from column 1 of the source rack,
• Dispense with tips 1-5 into column 1 of the destination rack,
• Wash tips 1-8.
Assign -1 to SAMPLE_CNT to deactivate the feature again.
11.1.3.8 TUBE_CNT
After executing a PosID command, Gemini writes the number of tubes scanned in the script so far to TUBE_COUNT.
11.1.3.9 WELL_OFFSET
This variable lets you modify the well selection for the basic commands Aspirate, Dispense, Mix and Move LIHA. Gemini shifts the well selection in the rack by the number of wells defined in WELL_OFFSET. If e.g. A1 to H1 of a microplate have been Figure 11-2: Using the SAMPLE_CNT variable
selected in the script and WELL_OFFSET is set to 8, Gemini will pipette in A2 to H2.
When applying the offset, Gemini shifts from rear to front and then from left to right.
Negative values of WELL_OFFSET shift the selection in the opposite direction. You can deactivate WELL_OFFSET by setting its value to 0.