SECTION 10: CIRCUIT DESCRIPTION
Part No. 715-0080, Rev. B
- 80 -
Potentiometer
R12
adjusts the DC level of the triangular wave, which controls the relationship between
error voltage and duty cycle. This allows
R12
to control maximum heater power. The diodes
CR13
and
CR17
allow the DC level of the triangular wave to be increased when the incubator is powered by
AC power. When AC power is used, the applied heater voltage is larger than when battery power or
external DC power is used. The higher DC level of the triangular wave results in lower duty cycle
applied to the heater for a given error voltage.
FAILSAFE TEMPERATURE LIMIT
The secondary thermistor and its independent circuitry provide a fail-safe heater disable function. The
secondary thermistor circuit is completely independent of the control loop. It has a completely
separate voltage reference (
Z2
) and amplifier (
Z3B
). A comparator (
Z3A
) is adjusted by means of
R15
to activate when a voltage corresponding to a temperature of 39.2
C is reached. This turns off
Q3
,
which opens the relay
K3
, and interrupts power to the heater. The
SYS FAIL
indicator will activate
and the audible alarm will sound.
ALARMS
Four comparators monitor the voltage derived from the primary thermistor. Comparator
Z11A
activates if the voltage is greater than 5 volts, indicating a shorted thermistor. Comparator
Z11D
activates if the voltage is less than 0.9 volts indicating an open thermistor. Activation of either of these
two comparators will turn on the
SENS FAIL
indicator, sound the audible alarm, and disable the heater
by turning
Q3
off.
Comparator
Z11B
activates when a voltage corresponding to a temperature of 39
C is reached. This
turns on the
SYS FAIL
indicator, sounds the audible alarm, and disables the heater.
Comparator
Z11C
activates when a voltage corresponding to a temperature of 38.5
C is reached.
This turns on the
HIGH TEMP
indicator and enables
Z13
, a 555 timer, which sounds an intermittent
audible alarm. The 555 timer
Z13
is configured as an asymmetrical square wave oscillator. It
establishes the repetition rate and duration of the intermittent audible alarm.
Comparator
Z7A
monitors the voltage level of the power source. If this voltage drops below 10.8 volts,
battery operation is assumed and the
LOW BAT
alarm is turned on.
Z13
is also enabled causing the
intermittent audible alarm to sound.
Содержание AirBORNE A750i
Страница 1: ...A750i Transport Incubator Service Manual...
Страница 6: ...Par rt No 715 008 80 Rev B LA ANGUAG GE DIS 4 SCLAIM MER...
Страница 7: ...Par rt No 715 008 80 Rev B LA ANGUAG GE DIS 5 SCLAIM MER...
Страница 8: ...Par rt No 715 008 80 Rev B LA ANGUAG GE DIS 6 SCLAIM MER...
Страница 9: ...Par rt No 715 008 80 Rev B LA ANGUAG GE DIS 7 SCLAIM MER...
Страница 10: ...Par rt No 715 008 80 Rev B LA ANGUAG GE DIS 8 SCLAIM MER...
Страница 11: ...Par rt No 715 008 80 Rev B LA ANGUAG GE DIS 9 SCLAIM MER...
Страница 12: ...Par rt No 715 008 80 Rev B LA ANGUAG GE DIS 10 SCLAIM MER...
Страница 102: ...S Par ECTION rt No 715 008 N 14 S 80 Rev B CONTROL SCHEM L BOARD S MATICS SCHEMAT DRAW TIC 001 51 WINGS 81 100...
Страница 103: ...S Par ECTION rt No 715 008 N 14 S 80 Rev B SCHEM PULSE MATICS OX DISPLA DRAW AY BOARD WINGS D SCHEMA ATIC 001 5 5193 101...
Страница 104: ...S Par ECTION rt No 715 008 N 14 S 80 Rev B SCHEM MATICS DRAW WINGS 102...
Страница 105: ...S Par ECTION rt No 715 008 N 14 S 80 Rev B SCHEM MATICS DRAW WINGS 103...
Страница 106: ...S Par ECTION rt No 715 008 N 14 S 80 Rev B SCHEM MATICS DRAW WINGS 104...
Страница 107: ...S Par ECTION rt No 715 008 N 14 S 80 Rev B SCHEM MATICS DRAW WINGS 105...
Страница 108: ...S Par ECTION rt No 715 008 N 14 S 80 Rev B SCHEM MATICS DRAW WINGS 106...
Страница 110: ...S Par ECTION rt No 715 008 N 14 S 80 Rev B SCHEM MATICS DRAW WINGS 108...
Страница 112: ...S Par ECTION rt No 715 008 SCHE N 14 S 80 Rev B MATIC PN SCHEM NEUMATIC MATICS C A750i CA DRAW ART 002 40 WINGS 010 110...