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5 CALIBRATION AND VALIDATION
of the calibration plate and perform a measurement in Static Mode. If these
values are regularly stored, this information can be used for monitoring of the
calibration/validations.
5.2.2 ISO Calibration plates (metal)
Select “Calibrate” from the Image Control Panel and place the PGX+
instrument on top of the semi- sphere and push the instrument gently
against the calibration plate surface. This “artificial droplet” is now measured
continuously. Enter the height of the reference found on the calibration
plate. If the data are inside the tolerances, all numbers will be displayed in
green. If one or more numbers are displayed in red, the instrument must be
re-calibrated
Your PGX+ instrument has been carefully assembled and checked during
production. It should not be necessary to do any further adjustments. For a
correct performance, however, the instrument must be calibrated according
to the procedure below. Without a correct calibration the instrument
readings will be incorrect.
NOTE:
Before calibration, your instrument should be connected to the USB port for
30-60 minutes in room conditions. Make sure the drop applicator is installed
to avoid stray light shining into the instrument as this may have an impact on
the calibration.
5.1
Calibration Procedure (Perspex plate)
a)
The steel ball must have its top 2.6-3.0 mm above the Perspex sur-
face. With a steel ball outside these dimensions calibration might fail.
b)
Select “Calibrate” from the Instrument menu
c)
Locate the reference mark at the edge of the instrument sole.The
calibration plate has a similar mark indicating the ”full sphere”.
Place the PGX+ instrument on top of the calibration plate with its
reference mark positioned above the dot as indicated in the picture.
Push gently on top of the instrument to make sure the instrument
rests firmly against the calibration plate surface.
d)
Click on the [Start] button to find the optimum Threshold setting.
e)
Next the automatic scale factors are determined from the image. This
is a high precision operation, which requires a clean sphere. If defects
are detected an error message ”Unable to find sphere” will appear. If
debris is found at the sphere contour, remove the instrument from
the calibration plate and clean the steel ball with a cotton swab
dipped in Isopropanol. Select “Camera” and “Calibrate” to restart the
calibration routine.
f )
When the calibration routine has terminated, the results are
displayed for the semi-sphere above the diameter with the following
target numbers:
- Height (c-top)
= 1,00 ± 0.02 mm
- Diameter
= 2.00 ± 0.04 mm
- Volume
= 2.09 ± 0.4 µl
- Contact Angle
= 90.0 ± 1°
NOTE:
Accepted values will appear in green.
g)
Click on [Save] to store the calibration data.
5.2
Validation Procedures
To verify a correct instrument reading it is much faster to “validate” the
instrument using one of the two validation procedures described below. It is
recommended to validate the instrument readings at regular intervals.
5.2.1 Standard Calibration plates (Perspex)
Select “Calibrate” from the Image Control Panel and place the PGX+
instrument on top of the full sphere and push the instrument gently
against the calibration plate surface. This “artificial droplet” is now measured
continuously. If the data are inside the tolerances, all numbers will be
displayed in green. If one or more numbers are displayed in red, the
instrument must be re-calibrated (Section 5).
NOTE:
An optional way to validate the instrument is to place the instrument on top
