Thermo Scientific 7451 Operating And Maintenance Manual page 41

Section 3
Configuration/Calibration
Menu Entry
Definitions (cont.)
3-6 Controlled Rate Freezer
D. Simulation:
This menu item enables a thermal simulator that allows the unit to
run freezing profiles in a realistic manner without actually using the
chamber heater or cooling solenoids. The simulator uses separate
parameters for heating and cooling effects that approximate the
performance of the real chamber.
The delays supported are:
• Turn On delay (Del)
• Turn Off delay (Eff )
• Rate of temperature change per minute (C/M)
Simulation mode is enabled by changing the "sim" parameter from
0 to 1, exiting the Simulation menu and cycling the AC power
Off/On. When the unit powers back up, "sim" will be appended to
the software version number on the initial power-on display of the
4 X 20 LCD. The simulation mode is disabled by changing the
"sim" parameter from 1 to 0, exiting the Simulation menu and
cycling the AC power Off/On. "sim" will no longer be appended to
the software version number on the initial power-on display.
E. Software Checksum
This menu item initiates a checksum calculation of the software in
controller memory and compares it to the reference value loaded in
the controller when the software was installed. In addition, the
checksum value is shown in the lower right corner of the display.
F. Test RAM
This menu item initiates a non-destructive test of all RAM on the
controller board (S-RAM, BAT-RAM). Any errors found would be
reported on the LCD display (i.e., "Memory failure, check UXX").
G. Thermal Controller
Adjust the cycle period of the thermal controller and integral
proportional, differential gain of the P.I.D. temperature controller,
the minimum solenoid on time, the temperature difference from
the setpoint that the Cool+ solenoid is actuated, and the difference
in P.I.D. parameters for the heater vs. LN2 injection cooling. Exit
this menu using the Back key.
There is a separate set of parameters for each size of chamber
available ([L] 1.7 cu ft, [M] 1.2 cu ft, and [S] 0.6 cu ft).
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