RADIOMETER TCM3 - Page 13

FCMS
and
1CM3U
Service
Manual
2.
TCM3
General Information, Continued
Main PCB
(continued)
Display PCB
Power Supply
199808-1
If
the
monitor
is
powered
from
the
built-in
NiCd
battery
only,
the
light-bar
is
activated
via
comparator
1,
indicating
that
the
function
time
of
the
Monitor
is
limited
to
approximately
3
hours
on
a
fully
charged
battery.
The
heat
supply
circuit
has
a
battery-low
terminal
which
is
activated
if
the
NiCd
battery
voltage
drops
below
7.0
V.
This
causes
the
BAT
light
bar
to
flash,
indicating
that
the
function
time
now
is
limited
to
approximately
10
minutes.
If
the
voltage
drops
below
6.5
V,
the
microcomputer
and
its
peripherals
will
be
reset.
The
microcomputer
system
consists
of
the
8-bit
CMOS
processor
NSC
800,
the
EPROM
(program
memory),
the
RAM
(data
memory)
and
the
input/output
peripherals
already
mentioned.
The
system
has
a
multiplexed
bus
structure
where
the
low
order
part
of
the
address
bus
is
shared
with
the
data
bus.
The
display
is
multiplexed
and
the
7-segment
display
data
are
latched
from
the
data-bus.
Includes
the
LED
display,
the
audio
transducer
for
the
acoustic
alarm,
the
electrode
holder
micro-switch
and
the
5
front
panel
keys.
If
the
mains
adapter
is
removed
from
the
monitor,
the
display
light
is
reduced.
This
reduces
the
power
consumption
and
thus
prolongs
the
function
time
of
the
monitor.
The
circuits
of
this
PCB
are
galvanic
isolated
from
the
rest
of
the
monitor
by
means
of
the
transformer
and
opto-couplers
on
the
Analog
PCB.
It
includes
a
switching
regulator
power
supply
system,
3
linear
DC
regulators
and
a
communication
circuit
for
the
analog
output
and
serial
data
input/output.
The
switching
regulator
has
a
combined
current
limiter/battery
control
circuit
which
disables
the
regulator
output
if
the
battery
voltage
decreases
below
6.2
volts.
Continued on next page
2-7