Semi-Micro Osmometer K-7400S instructions, V3700
Troubleshooting
28
Cause
Remedy
Too little sample solution is in the
sample tube. A very cold zone,
which causes self-freezing of the
sample, develops above the solu-
tion on the sample tube wall.
Use exact the required sample
volume: 50–150 µl
The sample tube or the thermis-
tor is scratched or contaminated.
Both could act as crystalliza-
tion nuclei causing premature
freezing.
Use a new sample tube and care-
fully clean the thermistor.
Only use sample tubes which
were obtained from KNAUER or
recommended by KNAUER.
Solutions saturated with air or
gases are sometimes difficult to
super-cool.
Degas the sample solution by
ultrasound.
Note:
Calibration and measurement have to be performed with the same
temperature settings and equal volume.
9.3
Non-freezing of the sample
If the sample does not freeze, one of the following causes may be
respon sible:
Cause
Remedy
The cooling rate is not sufficient.
Ensure that the air inlets and out-
lets at the device are free.
Too much sample solution is in
the sample tube. This leads to an
uncooled zone in the upper part
of the solution. The stirring causes
a mixing of warm and cold sample
layer.
Use exact the required sample
volume: 50–150 µl
If these solutions are not effective, the freezing temperature is too high
and has to be lowered. The freezing temperature can be changed in
screen 7 COOL see „7.9 Important operating notes“ on page 24).
Note:
Calibration and measurement have do be performed with the
same temperature settings and equal volume.
