Repair and Calibration of Pipettes - PAGE 2        

	c. Place the proper tip firmly on the pipette. Set the volume
to the maximum capacity by turning the dial to about five units
above the maximum then back down smoothly to the desired volume.
This reduces error due to backlash in the dial and screw. Press the
plunger down until a resistance is felt. Hold the plunger and
immerse the tip in the DI water 1-2 mm for the smaller pipettes and
2-4 mm for the P1000. Slowly release the plunger while holding the
pipette close to vertical. When the plunger is fully released, wait
2 seconds for the liquid to settle. Lift the pipette and check for
leakage; if the water drips out, the seals need to be replaced.
Check for any water clinging to the outer surface of the tip. If
there is any, carefully wipe it off without disturbing the liquid
inside. Check for air bubbles in the sample; if any, start over and
release the plunger more slowly.
	d. Zero the balance with the weighing container. Dispense the
water into the container slowly, then push the plunger past the
resistance to expell all of the water. Check that no water remains
in the tip. Cap the container and weigh. Repeat the procedure
several times and compare the reproducibility of your results with
the specifications in Table 1. The first sample may be different
because the plastic tip absorbs some water at first. Don't try to
change the calibration until you get reproducible readings. Erratic
readings may be due to poor technique, bad seals, a corroded
piston, or or other damaged parts.
	e. If the volume is consistently outside the specified limits,
the calibration needs to be changed. The method used depends on the
model. Older units have locking setscrews. Newer units have a
plastic calibration screw on the plunger rod.
	Older models: Turn the volume knob until the three setscrews
above the rubber ring are exposed. Do not touch the three setscrews
below the rubber ring. Use the 2mm hex wrench to loosen the upper
setscrews. Then use the special tool to turn the slot at the
plunger shaft. The slot is turned clockwise to reduce the volume.
Then lock the adjustment by tightening the three setscrews gently.
Reset the volume knob and check the volume using the balance.
	Newer models: Use the special wire tool to turn the plastic
screw with holes that surround the plunger rod. Insert
the tool tip fully into one of the small holes and turn the tool so
that it rotates the plastic screw. Turn clockwise to reduce the
volume. The adjustment is self-locking. Reset the volume knob and
check the volume using the balance.

Other Problems:
	The following problems are more difficult to fix. Turn
these in for repair.
	1. If calibration is not possible within the adjustment
range, the dial needs to reset.
	2. Bent plunger rods can be straightened.
	3. Cracked rubber friction rings can be replaced.