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Description
VACUUM SYSTEM
TEMPERATURE SENSING
TEMPERATURE CONTROL SYSTEM
1
Trademark of E. I. Du Pont de Nemours & Company.
1-6
The vacuum system is automatically activated when [
and [
] are pressed, or it may be turned on directly by pressing
START
the [
] key. Three vacuum LEDs, labeled 750, 200, and <20,
VACUUM
are located in the middle of the upper display to indicate the level of
chamber pressure in microns.
At the end of a run, the chamber vacuum must be vented (by pressing
[
]) before the door can be opened. After the door is opened,
VACUUM
the chamber is brought to approximate room temperature to prevent
condensation from collecting in the chamber. (To help keep the
chamber dry and clean, the door should be kept closed whenever
possible.)
A purge system removes significant amounts of moisture from the
vacuum pump and chamber. If it takes a long time to pull a vacuum,
however, it is likely caused by excess moisture in the system. Refer to
Section 4, for information on correcting this condition.
Rotor temperature is detected by a radiometer mounted in the bottom
of the rotor chamber (see Figure 1-2) when the chamber pressure is
below 100 microns. When above 100 microns (or if the radiometer
fails), chamber temperature is measured by a thermistor mounted in
the chamber.
The instrument uses a solid-state thermoelectric refrigeration and
heating system, which eliminates the need for a complex, conven-
tional refrigeration system and heater. Neither Freon
needed; the only coolant required is forced air from the cooling fans.
After the power is turned on, the temperature control system is
activated when the door is closed and the vacuum system is turned
on. The rotor temperature is controlled to ±0.5°C of the set value. If
the temperature system malfunctions, the TEMP diagnostic message
will appear and the rotor will decelerate to a stop.
]
ENTER/RECALL
1
nor water is
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Troubleshooting
