9 Error Messages and Troubleshooting
If the thermistor probe’s glass bead has even a hairline scratch that cannot be removed, replace the
sensor. Dirty measuring vessels (dust on the inside surface) can also cause such errors.
Measuring vessels that are re-used may eventually develop cracks in the plastic in which a fine liquid
film can cause premature crystallization.
Measuring vessels are designed for single use only. Re-use of measuring vessels can
lead to non-reproducible results.
9.3
Late or No Crystallization
After the sample solution has been cooled to the proper temperature, crystallization is initiated
automatically by the injection of ice crystals. There are two possible reasons for a crystallization failure:
9.3.1 Excessive Osmolality
Crystallization is initiated at -7°C.
The OSMOMAT auto can measure solutions with a maximum osmolality of approximately
3 Osmol
,
since this osmolale concentration yields a freezing point temperature of:
3 x 1.858 = 5.574
≈
–5.6°C
If the freezing point is very close to the temperature at which crystallization is initiated, however,
crystallization will not start despite the very effective method of initiation crystallization via the injection
of ice crystals. This condition is further exacerbated if the solution exhibits a rising viscosity.
The only remedy in such cases is to adequately dilute the sample solution.
It must be taken into consideration, however, that the osmolality does not change in proportion to the
dilution ratio, since the degree of electrolyte dissociation during dilution is different for each substance.
For routine measurements — e.g. quality inspections — corresponding relative measurement results
from diluted samples can be used as a basis for evaluation.
9.3.2 Injection with Ice Crystals Does Not Work
If no crystallization occurs during the crystallization-initiation phase despite the sounding of the
acoustic signal and even though the sample liquid does not exhibit excessive osmolality, there are
various possible causes. (See also 9.4 Classification of Malfunctions by Component Group).
1.
The stainless steel needle that transports the ice crystals is not moving from its upper to lower
position. A mechanical problem is preventing the movement of the needle.
Error Messages and Troubeshooting
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