Description of functions Servo-i Ventilator System
3 - 8 Service Manual Revision 02
3
PC 1784 Expiratory channel
Functional Main Blocks diagram marking: 'F'
The main block Expiratory channel comprises
microprocessor control to achieve measurement of
expiratory flow. The output signal Exp. Flow is used
in the main block Control.
Electronics including microprocessor (µP) for
handling of:
• All electronic connections to and from the
Expiratory Section functions.
• Measurement of airway pressures in both
Inspiratory Section and Expiratory Section.
• Control of the Safety Valve functions in the
Inspiratory Section.
A thermistor on PC 1784 monitors the temperature
inside the Patient Unit. An alarm is activated if the
temperature is 77 ±5 °C (170 ±9 °F) or higher.
Includes an ID PROM. The ID information can be
read by the Servo-i System.
Note: The System SW must be re-installed if PC
1784 is replaced.
PC 1771 Control
Functional Main Blocks diagram marking: 'C'
The main block Control comprises microprocessor
control of Breathing pattern for all different
ventilation modes.
Electronics including microprocessor (µP) control to
achieve:
1. Regulation of Inspiratory flow which is used
during inspiration time in Volume Control (VC)
mode.
2. Regulation of Inspiratory pressure which can be
used during inspiration time in any mode.
3. Regulation of a constant Inspiratory flow which is
used during expiration time in all modes.
4. Respiratory timing pattern including frequency as
well as distribution of the duration for Inspiration
time, Pause time and Expiration time according
to front panel settings.
5. Regulation of Inspiratory flow during inspiration
time. The desired total Inspiratory flow value
according to front panel settings is used to
generate the flow reference signals Insp Flow Ref
1 and Insp Flow Ref 2. The level relation between
these two flow reference signals depends on the
desired O
2
concentration according to front panel
setting. Insp Flow Ref 1 and Insp Flow Ref 2 are
used for the control of its respective Gas Module
(Air and O
2
).
Regulation of a constant Inspiratory flow during
expiration time: The desired constant Inspiratory flow
value is the default or preset Bias flow value (see
User’s manual).
This desired constant Inspiratory flow value is used
to generate the flow reference signals Insp Flow Ref 1
and Insp Flow Ref 2 with the same relation and same
handling as described above under ”Regulation of
Inspiratory flow…” except this occurs during
expiration time.
The electronics controlling the optional Servo Ultra
Nebulizer is located on PC 1771 Control.
Includes an ID PROM. The ID information can be
read by the Servo-i System.
Note: The System SW must be re-installed if PC
1771 is replaced.
A lithium battery on PC 1771 power supplies the
internal memory on the PC board. If the battery on
PC 1771 is disconnected or if the battery voltage is
too low, user default configurations made via the
Field Service System (FSS) and Pre-use check
results including transducer calibrations will be
erased. The lithium batteries must be replaced after
5 years.
PC 1772 Monitoring
Functional Main Blocks diagram marking: 'M'
The main block Monitoring comprises microprocessor
(µP) calculation of parameters and monitoring of
alarm limits with control of alarms (as well as back-
up alarm). The main block Monitoring cooperates
with the Loudspeaker in the User Interface.
The PC 1772 Monitoring handles all supervision and
alarms in the system. It activates pressure reducing
mechanisms, including activation of the safety valve,
in case of excessive breathing system pressure.
All alarms are conveyed and displayed on the front
panel and the alarm sound is also generated. In case
of malfunction in the loudspeaker located on PC
1777 Panel, a back-up sound generating device
(buzzer) on PC 1772 will be activated automatically.
This buzzer is monitored by a microphone at startup
and during the Pre-use check.
The following voltages are supervised:
• +24 V
• +12 V
• -12 V
• +5 V
• +3.3 V.
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