RADIOMETER TCM3 - Page 11

VMS
ana
FUMSU
Service
manual
2.
TCM3
General Information, Continued
Hardware
Analog PCB
199808-1
The
electronics
are
mounted
on
four
PCBs.
Please
refer
to
the
block
diagram
at
the
end
of
the
TCM3
part.
Monitor Drawing
TCM3 below R22 | 3759-A2, revision O
TCM3 from R22 3759-A2, revision 1
This
board
includes
the
electrode
input
circuits,
the
A/D
converters,
the
patient
safety
barrier
components
and
the
charging
circuit
for
the
NiCd
battery.
Signals
from
the
electrode
and
the
electrode
amplifiers
mounted
in
the
electrode
plug,
that
is,
the
pO2,
pCO,
and
thermistor
signals,
are
converted
into
pulse
signals
by
the
two
A/D
converters.
The
pulse
duty
cycle
represents
the
measured
value.
One
of
the
A/D
converters
is
common
to
all
parameters
via
the
input
multiplexer.
The
other
is
used
in
order
to
increase
the
speed
and
security
of
the
electrode
temperature
regulation
system.
The
electrode
temperature
is
measured
by
means
of
a
thermistor
which
is
part
of
a
temperature
resistor
bridge.
The
heat
power
is
measured
across
the
resistor
R,
and
the
microcomputer
is
informed
via
the
input
multiplexer
and
A/D
converter
1.
The
NiCd
battery
charging
circuit
adjusts
the
charging
current
according
to
the
monitor
consumption.
The
galvanic
separation
between
the
power
supply
board
and
the
rest
of
the
monitor
is
achieved
by
using
a
switching
power
supply,
and
opto-couplers
for
the
input/output
signals.
TCM3
below
R22
include
two
opto-couplers.
One
for
digital/analog
output
and
one
for
digital
input.
ТСМЗ
from
R22
onwards
includes
five
opto-couplers.
Two
for
the
input/output,
and
two
for
automatic
power
supply
regulation.
The
fifth
opto-coupler
is
transferring
on/off
information
from
the
on/off
switch
to
a
switching
circuit,
which
prevents
the
optional
battery
cassette
from
being
discharged,
if
it is not
dismounted
after
use.
Continued on next page
2-5