CSZ EZT-550, Инструкция по эксплуатации

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EZT-550 Controller Manual
15
Minimum Humidity Limitations
The standard humidity option provides a lower limit on humidity control relating to a 4.4°C (40°F) dewpoint. The
dewpoint refers to the temperature at which the air contains the maximum amount of moisture it can hold. When
a surface drops to that temperature or below, condensation can occur. The dewpoint varies logarithmically with
temperature and relative humidity. This means that at higher temperatures, a lower humidity level can be
obtained because the air can hold more moisture the warmer it becomes.
For example, an air temperature of 85°C (185°F) and relative humidity of 12%, is the equivalent dewpoint of air
at a temperature of 5°C (41°F) and 79%. Both of these values are at the minimum achievable dewpoint of the
chamber, and thus the minimum achievable humidity at the related temperature. If you were to set the humidity
setpoint at 0% for example, the humidity level would never reach 0 since the chamber is not capable of removing
any more moisture from the air.
The EZT-550 is programmed to determine what the minimum achievable humidity point is at any given
temperature and will control to that limit. Therefore, the system will not overwork itself trying to reach an
unattainable point. This prolongs system life and reduces wear and tear on humidity system components. Thus,
if you set a setpoint of 0%, you can be confident that the environment within the chamber will remain as dry as
possible at any given temperature within the operating range.
3.2.1 Chamber Options
The following information covers the use and operation of the optional chamber systems.
Aux Cooling
The auxiliary cooling system utilizes LN2 or CO2 as a boost cooling medium to assist the refrigeration system in
lowering the chamber air temperature. It is an inexpensive method for fast cooling transitions without having to
make the investment in a high horsepower refrigeration system that may rarely be used.
When this option is installed on the chamber, turn the Aux Cooling event on. When the boost is required during
a pulldown, the EZT-550 will turn on the boost cooling solenoids and inject LN2 or CO2, into the chamber to drop
the temperature as fast as possible. Once the setpoint is achieved, the boost solenoids will close in order to
conserve LN2 or CO2 since it is no longer required. To prevent the boost cooling from turning on for normal
testing, turn the Aux Cooling event off.
Dry Air Purge
The dry air purge event has two levels of functionality.
Level 1 - The first level of this option is dry air purge only. The purge only option consists of an air dryer
which dries a small volume of air and discharges the dry air within the chamber. This helps
reduce condensation on surfaces within the chamber by drying the air. When this event is
turned on with the purge only option, the air dryer will run continuously until the event is turned
off.
Level 2 - The second level of this option includes the frozen coil option. This option allows the chamber
to reach a –29°C (-20°F) dewpoint. This relates to lower relative humidity control. When the
frozen coil option is installed and the humidity system is enabled, the dry air purge system is
operated in conjunction with the frozen coil automatically by the EZT-550 controller based on
the air temperature and humidity setpoints. When required to obtain low humidity levels, the
frozen coil and dry air purge systems will start in order to obtain the target setpoint. When no
longer required, they will automatically turn off.
You also get the benefit of being able to manually use the dry air purge system by turning the
purge event on and off. However, in the case where the frozen coil option is installed, the
humidity system must be disabled for the dry air purge to function manually.