OTF 5000/HS/LS-001/2/3/4 Iss 4 June 2012
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3 Place the /QF cover over the /QF, this will reduce the rate that frost forms.
4 Switch the /QF on at least 30 minutes before it is required for use. Please note that in certain
conditions the /QF compressor will not operate immediately. This is because the operation of
the /QF compressor is dependant on the temperature of a heat exchanger, which is cooled
by the chamber cooling system. Once the chamber compressor has been running for a few
minutes the /QF compressor will operate and the /QF will start to cool.
Using the /QF
1 Wait until the /QF has reached a temperature of at least minus 70ºC before freezing
specimens. Although specimens will freeze at warmer temperatures the advantages of the
rapid freezing will be lost.
2 Apply a layer of embedding compound to the object holder (which must be above a
temperature of 0ºC), place the specimen on top of the object holder and then insert the
object holder into the sleeve of the /QF. While this is freezing through, but before the top
surface of the embedding compound goes solid, apply subsequent layers of embedding
compound if required. Once the specimen is frozen all the way through, remove the object
holder, complete with the specimen and place it in the vice jaws ready for sectioning.
Note
- the /QF is obviously very cold and if the object holder is left in it for some length of time
the specimen will achieve a temperature of -80ºC. If the specimen is then placed in the vice
jaws it will be far too cold to cut and if attempted, damage may occur to knives. It is imperative
that a little time is allowed for the specimen temperature to equalise before cutting commences.
Defrosting
Defrosting of the /QF is controlled by the cryostats defrost clock. It is recommended to select 30
minutes defrost each night.
Always switch off the /QF and remove its cover at the end of the day when defrosting is
required. Failure to do this will result in rapid frosting of the /QF once it starts working. This is
due to the increased humidity in the chamber and /QF resulting from the defrosting. Once the
chamber has cooled to its normal working temperature, this humidity will have reduced.
At the start of the day, switch on the /QF and replace its cover.
Temperature Calibration
The temperature display has been calibrated to read accurately between -70ºC and -80ºC. It
may read inaccurately at temperatures significantly out of this range (e.g. at room temperature).
2.1.9 /EC or /LT or /LOWEC - DUAL REFRIGERATION SYSTEM (where
applicable)
Press the DUAL button on the front panel to initiate use of both
compressors.
NOTE:
When running without the DUAL light illuminated, the
cryostat will automatically switch between one compressor and
the other in order to reduce wear on the ocmpressors.
Please note that there will be a pause of 40 to 70 seconds
between the compressors starting in order to reduce current
surges.
In the DUAL mode, full advantage can be taken of the extra refrigeration power available, and
an extra 5ºC can be achieved in the cryostats freezing performance.
FIG 11
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