Biotek MicroFlo select - Page 124

106 | Gravimetric Calibration Instructions
MicroFlo Select Microplate Dispenser
Determining the Amount of Rotation
The amount of fluid dispensed may be adjusted by increasing or decreasing the tension
in the tubing. A clockwise rotation of the adjustment screw increases tension on the
tubing and reduces the volume of fluid dispensed. A counter clockwise rotation
decreases the tension and increases the volume dispensed.
The amount of rotation, or number of turns of the screwdriver, required to change the
mass of fluid dispensed can be estimated as:
ected
ectedactual
m
mm
kTurns
exp
exp
)( 

Where
ectedactual
mm
exp
 is the difference between the actual mass and the expected
mass, and an experimentally derived calibration constant,
k , for each of the cassettes
which is approximately:
 1L Cassette:
7.60k turns
 5L Cassette:
3.51k turns
 10L Cassette:
6.42k turns
BioTek provides the Gravimetric Cassette Calibration Worksheet to facilitate the
calibration procedure. This Excel
®
spreadsheet uses this formula to recommend the
direction and number of turns of the screw required to calibrate the tube.
Accuracy Specifications
The accuracy specifications for the cassettes are intended to describe the performance
of tubing throughout its life. Typically, achieving a dispense accuracy that is 1/10
Th
of
the specified accuracy is the goal of calibration.
Dispense accuracy is computed using this formula:
ected
ectedactual
m
mm
Accuracy
exp
exp
)(
100(%)


Guidelines for Adjusting the Tension Screw
It is a trial and error process determining the correct position of a tube’s tension screw.
BioTek developed these guidelines to help, but hands-on experience is the only way to
become proficient at it.
 To give you a feel for the effect of the tension screws, this how a ½ turn of the
screw alters the tube’s volume:
Cassette Volume Difference
1 µL 10 µL .08 µL
5 µL 50 µL .5 µL
10 µL 100 µL 1 µL
  Turn the screw clockwise to reduce the dispense volume.
 Turn the screw counter-clockwise to increase the dispense volume.