Servo-i Ventilator System Description of functions
Revision 02 Service Manual 3 - 7
3
Bacteria filter and expiratory pressure tube
Via a Bacteria Filter inside the cassette, the
Expiratory Pressure Tube connects the cassette to
the Expiratory Pressure Transducer. The filter and
the connector are integrated parts of the cassette.
The filter protects the transducer on PC 1781
Pressure Transducer from contamination.
Expiratory valve
The Expiratory Valve consists of a membrane in the
cassette that is operated by the axis of the
Expiratory Valve Coil. The valve is fully open as long
as no power is supplied to the coil.
Operating capacity for the membrane is estimated to
10.000.000 breathing cycles. When this limit is
passed or if the membrane for some reason has
become defective, it must be replaced. Refer to
instructions in chapter 'Disassembling and
assembling'.
Remaining operating capacity (in %) for the
membrane can be shown in the Status window.
Select Status / Exp. cassette to check 'Remaining
membrane capacity'. The operating capacity meter
must be reset after replacement of the membrane.
Expiratory valve coil
The movable axis of the Expiratory Valve Coil
controls the opening of the Expiratory Valve by
pushing the valve membrane into desired position.
The power supply to the coil is regulated so that the
remaining pressure in the patient system, towards
the end of the expiration time, is kept on the PEEP
level according to front panel setting.
Expiratory outlet with expiratory one-way valve
The gas from the patient system leaves the ventilator
via this Expiratory Outlet. Backflow via the cassette
is prevented by the Expiratory One-Way Valve. Its
rubber membrane and valve seat are integrated parts
of the Expiratory Outlet.
PC 1786 Expiratory channel cassette
The PC 1786 Expiratory Channel Cassette is a
connection board, integrated into the Expiratory
Cassette, for the Ultrasonic Flowmeter and for the
Heating Foil. It connects to PC 1785 mounted in the
expiratory cassette compartment.
Includes an ID PROM. The ID information can be
read by the Servo-i System.
PC 1785 Expiratory channel connector
The PC 1785 Expiratory Channel Connector is a
connector board including signal filters that is
mounted in the expiratory cassette compartment.
It connects to PC 1786 mounted in the Expiratory
Cassette when the cassette is docked to the
expiratory cassette compartment.
PC 1770 Main back-plane
Interconnection board for the PC boards in the lower
part of the patient unit.
The ventilators System ID (Serial No.), configuration,
time stamp for preventive maintenance, etc, is stored
in an EEPROM on PC 1770. Thus, when replacing
PC 1770, a spare part that is factory programmed for
the concerned ventilator must be used.
As the preventive maintenance time stamp will be
reset when replacing PC 1770, a new time stamp
must be set via the Biomed menu. In order to make
this new time stamp correct, the preventive
maintenance must be performed. Refer to chapter
'Preventive maintenance'.
Pressure transducers
Functional Main Blocks diagram marking: 'T'
PC 1781 Inspiratory pressure transducer
The pressure, conveyed via the pressure tube
connected to this block, is led to and measured by
its differential pressure transducer. With differential
reference to the ambient pressure, the output signal
is proportional to the measured pressure thus giving
a linear measurement in the range -40 cm H
2
O to
+160 cm H
2
O.
Technical limitation: Pressure exceeding ±400 cm
H
2
O must be avoided.
Includes an ID PROM. The ID information can be
read by the Servo-i System.
PC 1781 Expiratory pressure transducer
Function identical to PC 1781 Inspiratory Pressure
Transducer.
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