Thermo Scientific 7452 Operating And Maintenance Manual page 39

Section 3
Configuration/Calibration
Menu Entry
Definitions (cont.)
3-4 7007452 CryoMed Freezer
2. Probe Scaler:
The Chamber and Sample probe scale factor (scaler) can be
adjusted over a range of 0.5000 to 1.9995 in 0.0005 increments.
Adjust the probe scaler for a -196°C temperature display reading
with the probe in liquid nitrogen.
Warning Contact of liquid nitrogen with the skin or eyes may cause
serious freezing (frostbite) injury.
Thermocouple Probe Calibration Procedure:
Note A container of "pooled" liquid nitrogen and a container of crushed
ice and water (crushed ice just covered with water) are required for this
procedure. Prepare both containers before starting the procedure.
1. Turn the unit on and enter the Configuration/Calibration menu. Allow
the unit to warm-up for 10 minutes.
2. Remove the end of the chamber thermocouple probe from the
mounting tube (near sample thermocouple connector inside the
freezing chamber).
3. Dip the Chamber and Sample probes in the water/ crushed ice
container and allow to stabilize for 5 minutes. The probes must be in
the center of the container, well away from the container walls.
4. Observe the Chamber and Sample temperature displays. Adjust the
Chamber and Sample 'Offset' parameters so that the displays each read
0.0°C. Move the cursor to the proper parameter by using the Enter/
Back keys and change the parameter using the up/down arrow keys.
Each degree or tenth of a degree of Offset will result in a respective
change in the corresponding temperature display.
5. Dip the Chamber and Sample probes in the liquid nitrogen container
and allow to stabilize for 5 minutes. The probes must be in the center
of the container, well away from the container walls.
6. Observe the Chamber and Sample temperature displays. Adjust the
Chamber and Sample 'Scaler' parameters so that the displays each read
-196°C. If several scaler values result in the desired reading, select a
scaler value in the middle of the range.
7. Repeat Steps 3 through 6 as necessary until both temperature displays
read 0.0°C and -196°C. There may be some interaction between the
'Offset' and the 'Scaler' adjustments.
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