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Hill-Rom Isolette C2000 - Analog;Digital (A;D) Conversions; Controller

Hill-Rom Isolette C2000
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Theory
of
Operation
Chapter
3:
Theory
of
Operation
Analog/Digital
(A/D)
Conversions
The
A/D
converter,
U11,
is
an
8-channel,
12-bit,
serial,
interface
device.
Control
for the
channels
is
software
configurable
by
the
serial
communication
line
SSPCLK,
ADCDIN
and
COMOUT.
The
A/D
converter
is
enabled
for
signal
processing
by
the
signal
ACENI,
which
is
asserted
twice
every
21
milliseconds
(the
A/D
converter
is
read
twice).
In
addition,
the
ADCIN
and
COMOUT
are
also
driven
at
21
millisecond
intervals.
The
SSPCLK
is
shared
with
the
EEPROM
on
the
sensor
board
and
scale
clock;
therefore,
the
timing
is
not
periodic.
All
temperature information
is
presented
as
a
multiplexed
signal
on
Channel
0,
and
oxygen
information
is
presented
as
a
multiplexed
signal
on
Channel
2.
Channel
4
allows
the
A/D
converter
to
read
its
maximum
input,
and
Channel
5
allows
the
A/D
converter
to
read
its
minimum
input.
This
allows
determination
of
proper
A/D
functioning.
The
analog
representation
of
fan
pulses
is
applied
to
Channel
6.
Controller
The
controller
is
designed
to
accept
input
voltages
between
the
range
of
90V
AC
and
264V
AC.
This
is
accomplished
by
the
use
of
a
universal
input
switching
power
supply.
Voltages
above
the
safe
operating
range
are
clamped
using
transorb
diode.
The
controller
is
designed
to
accept
input
frequencies
between
the
range
of
48
Hz
to
62
Hz.
This
is
accomplished
by
the
use
of
a
universal
input
switching
power
supply.
The
stand
supplies
the
input
power
and
protective
ground
to
the
controller.
The
stand
incorporates
a
15A
circuit
breaker
and
EMI
filtering
components.
The
controller
provides
AC
power
to
the
heater
and
the
humidifier.
These
outputs
are
fused
in
the
controller
to
protect
the
controller
in
the
event
of
a
short
circuit
or
electrical
overload.
¢
Maximum
heater
voltage—264V
AC
+
Maximum
heater
current—4.8
A
+
Maximum
humidifier
voltage—264V
AC
+
Maximum
heater
current—1.2
A
Heater/humidifier
fuse
rating
—6.3
A
Page
3-
16
Isolette®
Infant
Incubator
Service
Manual
(man223rf)

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