Hospira LifeCare XL Series, Техническое и сервисное руководство

Страница: 33 / 278

SECTION 4 THEORY OF OPERATION
430-00587-008 (Rev. 2/05) 4 - 8 Plum XL Series
4.2.3.3
ALARM CIRCUITRY (XL)
The alarm circuitry includes an oscillator circuit consisting of inverters U10C, U10B, and
U10E. The oscillator circuit generates acoustic power at a predetermined frequency based
on the BUZ1 self resonance. Normally, the BUZZER signal is low, U9-10 is high, and
resistor network RN8-7 and RN8-8 disables the oscillator. The alarm can be activated by
the BUZZER or *RESET signals becoming active and pulling RN8-7 down. When SW1 is
set to LO, resistor R13 is electronically connected to the BUZ1-3 (buzzer drive) and the
sound level decreases. U10D and U10F constitute a memory unit that disables the
oscillator circuit when the U10F output is high.
At AC (mains) power-up, POWERHOLD becomes active and changes the U10D/U10F
memory unit to enable the oscillator circuit. At a voluntary power-off, DIST_AIR_EN and
PROX_AIR_EN become momentarily active. This momentary activation of DIST_AIR_EN
and PROX_AIR_EN allows the memory unit to change to an oscillator-disabling state and
the alarm does not sound. At a catastrophic failure, however, the memory unit remains
enabled and the alarm sounds.
During a catastrophic failure, the alarm can be disabled by positioning the infusion system
control knob to OFF/CHARGE.
4.2.3.4
ALARM CIRCUITRY (XLM)
The alarm circuitry includes an oscillator circuit consisting of inverters U10C, U10B, and
U10E. The oscillator circuit generates acoustic power at a predetermined frequency based
on the BUZ1 self resonance. Normally, the BUZZER signal is low, U9-10 is high, and
resistor network RN8-7 and RN8-8 disables the oscillator. The alarm can be activated by
the BUZZER or *RESET signals becoming active and pulling RN8-7 down. U10D and U10F
constitute a memory unit that disables the oscillator circuit when the U10F output is high.
At AC (mains) power-up, POWERHOLD becomes active and changes the U10D/U10F
memory unit to enable the oscillator circuit. At a voluntary power-off, DIST_AIR_EN and
PROX_AIR_EN become momentarily active. This momentary activation of DIST_AIR_EN
and PROX_AIR_EN allows the memory unit to change to an oscillator-disabling state and
the alarm does not sound. At a catastrophic failure, however, the memory unit remains
enabled and the alarm sounds.
During a catastrophic failure, the alarm can be disabled by positioning the infusion system
control knob to OFF/CHARGE.
The alarm circuitry provides sound for low-level settings only. For high-level sound, see
Section 4.2.4, Buzzer PWA (XLM) .
4.2.3.5
ALARM POWER BACKUP CIRCUITRY
The alarm power backup circuitry is provided through super capacitor C34. C34 offers
power backup in the event of a catastrophic failure. Diodes CR15, CR19, and CR20 route
the power for alarm driver U10 from VDIG or C34.