PASCO ME-6940 Diffusion-Osmosis Apparatus - Manual (Page 4)

M o d e l N o . M E - 6 9 4 0 U s i n g t h e A p p a r a t u s
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• Ensure that the two holes of the membrane are lined up with the pegs on the cylinder and then carefully place
the other cylinder against the membrane so that the two raised pegs on the second cylinder go into the two
empty holes on the membrane. Ensure that the membrane is securely in place between the two O-rings, all
four raised pegs are inserted into the membranes holes and the membrane is pulled tightly across the space,
with no folds or gaps. Make sure that the two alignment tabs near the top of the cylinders are aligned.
• Quickly and carefully, screw in the four bolts and ensure that they are tight. The two cylinders should be
tightly secured to each other with the membrane separating the space between the two cylinders.
*You may wish to label the two cylinders (1 & 2) with a sticker or marker. This will help reduce confusion if
the solutions are similar in color.
4. Fill the cylinders: Immediately after placing the membrane in the apparatus, fill the cylinders with your solu-
tions. Do not allow the membrane to dry out! Pour the required amount of solution into the first cylinder. Tilt the
apparatus in all directions (careful not to spill the solution) to allow any bubbles in the bottom of the cylinder to
escape. Repeat with the second cylinder. If you expect the volume within the cylinder to increase during your
experiment, do no fill the cylinder with greater than 60 mL of solution, as the solution will overflow, or enter the
plastic tubing and harm the sensor.
If you are using a Dual Pressure Sensor (or other PASPORT pressure sensor) in your experiment, place the
blue cap into the first cylinder, press it down and then turn the cap to seal the cylinder. Repeat with the second
cylinder.
5. Set up your interface: Connect the sensor to the interface. View
Absolute Pressure 1, Absolute Pressure 2 and 1-2 Differential pres-
sure in a digits display. Also view 1-2 Differential Pressure in a
graph display.
6. Reduce the sampling rate: Because diffusion and osmosis experi-
ments take time, reducing the sampling rate of the sensor is neces-
sary so that the interface is not overloaded with massive amounts of
data. The default sampling rate of the PASPORT Dual Pressure
Sensor is 10 Hz (or 10 samples per second). Reduce the sampling
rate to 1 or 2 samples per minute.
7. Connect the apparatus to the sensor: Attach the quick-release
connectors at the ends of the two plastic tubes to the Dual Pressure
Sensor. (See Figure 3.) After you connect the apparatus to the pres-
sure sensor, allow the system to equilibrate for five minutes before
beginning data collection.
8. Calibrate the sensor: If you are using the PASPORT Dual Pres-
sure Sensor, calibrate Absolute Pressure 1 and Absolute Pressure 2
Membrane
Cylinder
Peg
Peg
Figure 2
Figure 3
Dual Pressure
Sensor