17
Target limits
When a test result is expected to fall within a
specific range, the corresponding min and max
values can be entered into these fields. When a test
result falls outside the specified range, this value
will appear in red.
Calibrate
The automatic calibration is used to determine the
correct light settings and the exact size of an
artificial droplet placed in front of the camera.
For a detailed description of the calibration
procedure, see Section 4.1.
9.2
The Main program
This section describes the functions available in the main program screen.
Static Mode
is designed to capture a single reading of the static contact angle at ”equilibrium”.
This value can be measured on smooth, non-porous surfaces not penetrated by the
test liquid. Typical examples are water droplets on hydrophobic release papers and
polymer barriers (e.g. liquid container board).
Dynamic Mode
captures a video sequence during the interaction between the liquid and the surface.
Here the dynamic wetting (contact angle), liquid penetration (volume) and
spreading are measured as a function of time.
Advancing Mode
is designed to characterise the “wetting hysteresis” as a liquid droplet advances
across a dry surface and then retracts from a wet surface. This measurement
requires a reversible pump flow, which is not possible to do with the micro pump
built into the PGX+Measuring Head.
SuperLow Mode
is designed for measurement of very low static contact angles below 10 degrees
related to super clean surfaces.
View Mode
produces a report from previously saved data.
Surface Tension
enables testing of the purity of the test liquid.
A sufficiently big pendant droplet is pumped out at the dispensing tip and the
surface tension is determined from the droplet shape.
Surface Energy
must be determined from calculations using contact angles. Different models exist
for these calculations using one, two or more liquids in specific combinations.
Options
opens a window with the current configuration settings and additional help text.
This screen is also used for diagnostics and selection of different languages.
Fig. 9.4 Image Control Panel with Targets
