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1 PG DOSING UNIT
The PG Dosing Unit is a standalone pumping device designed to deliver
liquid droplets from a disposable one mL syringe. Before you start using the
Dosing Unit, please take a few minutes to read these guidelines to familiarise
yourself with the different functions
1.1
Unpacking
The PG Dosing Unit is delivered in a hard case including the following
accessories:
- Five disposable syringes
- Five PTFE tubings 1.5 / 0.9 mm with PINK dispensing tips
- Five PTFE tubings 1.5 / 0.5 mm with RED dispensing tips
- Five PTFE tubings 1.5 / 0.2 mm with LILAC dispensing tips
- 12 VDC power adaptor for 100-240VAC
1.2
Power connection
Connect the power adaptor to an electrical outlet of 100-240 VAC.
1.3
Filling the liquid system
Fill the syringe with the selected test liquid. Liquids similar to water can be
filled with the tubing attached to the syringe. Higher viscosity liquids must
be filled with the dispensing tip removed.
Alternatively, liquids of high viscosity can be poured into the syringe after
the plunger has been pulled out from the syringe.
Turn the syringe with the tip pointing upwards and tap gently on the
dispenser to bring air bubbles inside the liquid to the top. Push the plunger
slightly forward to remove the air at the tip.
Make sure there are no visible air bubbles inside the liquid system.
To avoid contamination it is recommended to use separate
dispensing units for each test liquid!
1.4
Installing the syringe
Line up the moving pusher with the MODE selector in position F (Fill) and
press one of the buttons FWD or REV. A momentary key press will adjust the
position a short distance.
If one of these buttons is kept depressed the pump will switch into a higher
speed. In the reverse direction the pump will then continue until it reaches
the end position unless one of the keys FWD/REV is pressed a second time.
Insert the syringe into the PG Dosing Unit and tighten the locking screw
firmly at the end of the piston.
Insert the tubing end into the PG instrument so it extends slightly outside
the visible end of the drop applicator. Then tighten the locking nut.
PG Dosing Unit – GuideLines October 19, 2007
1.5
Selecting an Operation Mode
The PG Dosing Unit offers different pump modes. Some of these will pump
out a fixed, preset droplet volume whereas other modes are programmable
by the operator. Some of the programmable modes are based on a pump
cycle where the pump will reverse automatically to offer measurements of
wetting hysteresis using the advancing/receding contact angle method.
The list below describes the available operating modes:
FILL (F)
is used when a new syringe is loaded into the PG Dosing Unit.
- Press button FWD/REV momentarily to pump out a small volume
- Keep button FWD/REV pressed to enter high-speed motion.
To stop the REV motion before it reaches the end position, press the FWD/
REV button a second time.
FIXED ( 2/ 4/ 8 )
pumps out a single droplet of the preset size.
If the mode selector is switched to one of these positions, the indicator light
remains green.
Press the FWD button to pump a droplet of the preset size.
SINGLE (S1, S2, S3)
pumps out a single droplet of programmable size.
If the mode selector is switched to a position with a programmed volume,
the indicator light remains green. Press the FWD button to pump out the
programmed volume. If the selected position has no programmed volume,
the indicator light becomes orange and no pump action can be initiated
with the FWD button. To program a new droplet volume, press REV + FWD
and the indicator will start to blink. Press the FWD button one or more times
to enter the new droplet size. When the REV button is pressed, the new
droplet size is stored and the indicator turns green.
CYCLE (C1, C2, C3)
offers programmable pump cycles.
A pump cycle contains three phases; advancing, receding and ’top-up’.
The initial ‘advancing’ phase pumps out liquid and the growing droplet
advances across the dry surface. At the programmed droplet size, the pump
halts for a short while before the pump flow is reversed. Now the decreasing
droplet will recede from the wet surface until the droplet has lost
its contact with the surface. Finally, the ’top-up’ phase reverses the pump flow
again and a small volume is pumped out to restore the missing liquid volume
at the dispensing tip before the next pump cycle.
If the mode selector is switched to a position with a programmed cycle, the
indicator light remains green. Pressing the FWD button once then carries out
the complete pump cycle.
If the selected position has no programmed volumes, the indicator light
becomes orange and no pump action can be initiated with the FWD button.
To program a new droplet volume, proceed as follows:
a) Press REV + FWD and the indicator will start to blink.
b) Press the FWD button one or more times to enter the advancing droplet
size.
