Controls, Indicators, and Displays
SORVALL
®
Centrifuges
3-10
establishing blood bank protocols, for optimized braking with minimal
resuspension, we recommend starting at setting 5 and adjusting
up or down as needed. Selection of BRAKE OFF will have an
affect on SLOW STOP (see the NOTE under BRAKE OFF).
• BRAKE OFF deactivates normal deceleration braking for a
coasting stop from any specified speed (in rpm) between 4700
and 0. BRAKE OFF transition speed is set independently of set
run speed, and is not affected by changes to set run speed. If the
transition speed is set higher than the set run speed, at run
termination, the centrifuge will coast to a stop from set speed.
NOTE If SLOW STOP and BRAKE OFF are both selected:
– If the BRAKE OFF transition speed is set to 500 rpm
or higher, the SLOW STOP selection will be ignored.
– If the BRAKE OFF transition speed is set below 500
rpm, the centrifuge will decelerate with full braking to
500, transition to the specified SLOW STOP rate,
then change to a coasting stop when the specified
BRAKE OFF transition speed is reached.
• CHANGE OVERTEMPERATURE LIMIT allows changing the
maximum allowable sample temperature to establish a new
overtemperature offset value. The centrifuge calculates the
difference between the set and the maximum temperatures, and
retains that value as an offset to apply to future runs, until it is
changed. The retained offset will apply to any normal (manual-
entry) runs as well as to any recalled program runs (specific
overtemperature limit settings cannot be saved in run programs).
See the EXAMPLE at left.
During a run, if the calculated sample temperature in the RUN
display goes above the maximum allowable sample temperature,
a SAMPLE TEMPERATURE OVER LIMIT message will appear
in the SET display, and an alarm will sound. This may indicate
a condition requiring simple corrective action, or it could indicate
a refrigeration problem (see "SAMPLE TEMPERATURE OVER
LIMIT" on page 3-16).
This overtemperature alert is not activated and a precool mode
begins if the RUN display temperature is more than 2°C over the
SET value when START is pressed, or when a temperature change
between programs occurs in a STEP RUN. In each case, a SAMPLE
OVERTEMP – PRE-COOLING message will appear and an alarm
will sound. Pressing CLEAR removes the message and shuts off the
alarm, allowing the run to continue as a precool run (P-COOL
replaces DEG C as the field header in the SET display during precool
mode). A precool mode is automatic during a QC RUN; the message
and alarm are disabled, and the program is repeated until temperature
is within 2° of set.
EXAMPLE:
If you have a set temperature of 22
and set the maximum temperature to
24, an overtemperature alert will occur
if the calculated sample temperature
reaches 25. If the set temperature is
then changed to 4, the maximum
temperature setting will automatically
change to 6, based on the previously
calculated offset value.
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