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Static
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
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
is designed to characterize 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
is designed for measurement of very low static contact angles below 10
degrees related to super clean surfaces.
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.
Wettability
is a dynamic test with specific calculation for wettability.
7.2.2 Camera settings
Gain offset
This feature modifies the live camera image in real time. This way the full
dynamic range is always available even when the test substrate appears ”too
dark” or ”too bright” due to variations in light reflectance.
Double click on the label “Gain Offset” to restore the default value (24).
Exposure offset
This feature modifies the live camera image in real time. This way the full
dynamic range is always available even when the test substrate appears ”too
dark” or ”too bright” due to variations in light reflectance.
Double click on the label “Exposure Offset” to restore the default value (0).
Enhance
This feature brings out the droplet image even in situations where the
droplet base is partially hidden on a dark, light-absorbing surface.
When a water droplet is applied on a surface of low reflectance (e.g. dark,
rough craft liner), the droplet base will appear against a dark background.
If the light level is increased, or the parameter camera Offset Gain and/
or Offset Exposure are adjusted to distinguish the droplet base from its
background, the droplet top can become too bright against the illuminated
background. This is where the image enhancing routine will be very helpful.
•
Double click on the label “Enhance” to restore the default value (0).
•
Place the instrument on the test surface and apply a liquid droplet
on the surface.
•
Double-click in the video image to switch from greyscale to a binary
image if necessary.
•
Adjust the Camera Gain control until the top of the droplet is com-
pleted. Then use the Enhance control to create a solid black contour
all the way down to the base of the droplet.
