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freeze-pulse vibration blur at the very tip of the stir/freeze wire
should span at least 1/2” or 13 mm for one second, then cease.
If the freeze vibration is inadequate, do not proceed further but refer
the problem to a qualified service person with a 3900 service manual,
or telephone for Hot-Line® service as recommended in
Troubleshooting & Service.
If the freeze vibration is adequate, check and adjust the stir vibration
amplitude as follows:
j. With “
[stir] [freeze] ” displayed while running the stir/freeze test,
press the < button. The vibration blur at the very tip of the
stir/freeze wire for proper sample stirring of .2-mL to .3-mL sam-
ples should be between 1/8 and 1/4”, or between 3 and 6 mm.
That amount of stirring is necessary to minimize temperature gra-
dients in viscous samples, but more than 1/4” or 6 mm can cause
poor repeatability or frothing which may make it impossible to
reliably determine the freezing point of certain samples.
k. If the stir vibration amplitude is not correct, press STOP twice to
exit the TEST menu and press SETUP to enter the SETUP menu.
l. At “ Select Setup Item ”, press the START button. The display
will change to “ Setup Menu #: 0 ”.
m. At “ Setup Menu #: 0 ”, press the 4 button, then press ENTER.
The display will change to “ Set Stir Amplitude ” (this menu item
may alternatively be located by stepping forward or backward
from “ Select Setup Item ” with the > or < button).
n. At “ Set Stir Amplitude ”, press the START button. The stir/freeze
wire will begin to vibrate and the display will change to
“ Amplitude = xx ”, with “ xx ” being some two-digit number
around 50.
o. Looking across the stir/freeze wire toward the probe, you should
be able to see a stir vibration blur at the very tip of the stir/freeze
wire. For .25-mL osmometer operation, the stir vibration blur at
the very tip of the stir/freeze wire should be between 1/8 and
74
The Advanced
®
Osmometer Model 3900 User’s Guide