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2.4. FORMAT 550 DIGITAL CHANNELS
The Format 550 programming system fitted to the cabinet has the following digital
channel functions. A number of the channels are for the control of the cabinet and are
usually automatically selected on or off by the programmer as required to achieve
particular conditions. If applicable, other user designated channels are also detailed
below. All digital channels are shown on the monitor and program screens of the Format
550 programmer.
Full operating instructions for the Format 550 programmer are given in Part 2 of this
manual.
DIGITAL CHANNEL 1 COOLING (MAIN) *
SYSTEM CHANNEL
This channel switches the main cooling mode on (see section 3.2). The main cooling
mode is used to:
a) enable programmed temperature pull down from +70°C, ie: the fall rate is controlled.
b) enable freejall temperature pull down from the cabinet's maximum temperature, ie:
the fall rate is as fast as possible.
c) enable temperature dwells below +40°C (auxiliary cooling is used between +40°C
and +15°C if high humidity control is required).
d) extract heat dissipated from the test load between +70°C and the minimum operating
temperature.
e) enable the cooling coil's low surface temperature to dehumidify the cabinet between
+5°Cand+70°C.
DIGITAL CHANNEL 2 COOLING (AUXILIARY)
SYSTEM CHANNEL
This channel switches the auxiliary cooling mode on. The indirect cooling mode is used
to:
a) control temperature dwells with high humidities between approx. +15°C and +60°C.
b) extract heat dissipated from the test load during temperature dwells. The capacity of
the auxiliary cooling mode to extract heat from the test load is limited.
DIGITAL CHANNEL 4 HUMIDIFIER (VPG)
SYSTEM CHANNEL
This channel determines when "steam" injection from the vapour phase generator system
is available to the program controller.
This channel is always enabled when a humidity setting is programmed into the Format
550 programmer.