c)
Defective thermistor
This is the most frequently occurring error. There are two possible causes:
1. The thermistor is (has been) broken off: This can be recognised by the display
constantly, without any change, showing a negative value.
2. The glass shell of the thermistor is showing hairline cracks and is leaky: This
manifests itself with extremely unstable measuring behaviour. The repeatability is
very bad, e.g. fluctuations from approx. 20 m°C to 100 m°C.
In both cases, the thermistor must be replaced.
d)
Agitator error
a) The agitator is not oscillating freely:
The agitator must be able to move freely in the slot provided for it. It must never touch the
thermistor at any point. This must be paid particular attention to during thermistor
replacement.
b) The agitator amplitude is not large enough:
Cooling the sample is not performed evenly and clearly lasts longer than 90 seconds. With
a correctly adjusted agitator, the cooling time is almost about 90 seconds. The agitator
amplitude must be approx. 2 mm.
c) The agitator amplitude is too large:
Premature freezing of the sample happens often.
The agitator must be readjusted if needed.
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