MULTIPLE-KEY FUNCTIONS
(Cont’d)
While learning to use the keypad, remember that if you press the RUN key to begin a grinding
sequence when there is no liquid nitrogen in the mill, the liquid nitrogen sensor will shut down
the controls, the fault indicator will blink, and the display will flash “LN” for Liquid Nitrogen.
To restore the normal control display, press ENT (enter). To operate the mill, place a vial in the
coil, fill the tub to the mark with liquid nitrogen, and press RUN. Note that with no vial in the
coil, the Freezer/Mill makes no noise when the coil is energized. The only indication it is
running will be in the LED displays.
DO NOT RUN THE UNIT WITHOUT THE VIAL AND IMPACTOR, OTHERWISE THE
COILS MIGHT BE DAMAGED.
CONTROL MODES and CONDITIONS
Through its keyboard the 6750 Freezer/Mill can be programmed in program mode, operated
according to program in automatic mode, interrupted by stop mode, and tested manually in
manual mode. A pause condition occurs voluntarily when the operator decides to interrupt
(rather than stop) an automatic grinding cycle. A lid fault condition occurs automatically when
the lid of the mill is not properly shut. A liquid nitrogen fault condition occurs when there is no
liquid nitrogen in the tub, or not enough liquid nitrogen to chill the coil properly.
Program Mode: When the Freezer/Mill is switched on for the first time it will display (and
operate according to) the preprogrammed factory settings. These settings are:
Cycles (CYC) 3 Grinding Time (T1) 2 (min.) Pre-Cooling Time (T3) 15 (min.)
Impact Frequency
(RATE)
10 Cooling Time (T2) 1 (min.)
Cycles, grinding time, and impact frequency appear automatically in the LED display. Cooling
time appears when the T2 key is pressed, and pre-cooling time when the T3 key is pressed.
The user, following the instructions for programming, may change any of these five settings.
Changes in control settings go into temporary memory when the ENT key is pressed. They will
stay there until the mill is switched off, or can be transferred from temporary into permanent
memory by pressing the ENT and 0 keys simultaneously. When the mill is switched on, the
most recently stored permanent settings will recur, with the exception of impact frequency that
always reverts to 10.
Under normal conditions the Freezer/Mill is in Program Mode when switched on, and will
remain there until the mill is run, the liquid nitrogen level drops enough to trigger the LN sensor,
or a lid default condition occurs. At the end of a programmed run (Automatic Mode) the mill
will automatically return to Stop Mode and then Program Mode. If the mill is in any other mode
or condition (the display shows ”LID” or “LN”), the fault must be corrected and the mill must be
returned to Program Mode before it can be started again. If the fault condition is corrected and
the display remains in a fault state, press ENT.
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