Service manual

72 Siemens-Elema AB E382 E380E 061 01 03 01
Description of functions Servo Ventilator 300/300A
2
is situated on the 14.4 EXPIRATORY FLOW
AMPLIFIER
. The more flow in the channel, the
higher the pressure on the strain gauge. The
change in resistance in the Wheatstone
bridge is converted to a corresponding
signal voltage.
A resistor, 220 Ohms, 6W, is moulded into
the transducer and is used for heating of the
expiratory flow transducer. The transducer is
heated to approximately 40
o
C (104
o
F) to
prevent condensation of water vapour. The
heating is controlled from the main block
18 EXP. FLOW LINEARIZATION. If water should
condense in the expiratory flow transducer,
the resistance of the wire mesh net
increases. Thus the output signal will
increase. This can be seen on the digital
display and the bargraph for EXPIRED MINUTE
VOLUME
, as an increased reading. The
accumulation of medicaments, mucus and
secretion in the expiratory flow transducer
gives the same result.
For details on cleaning and calibration of the
flow transducer, see the chapters Routine
cleaning and Calibration in the Operating
Manual. Service interval 1000 h of operation
for exchange of the wire mesh net.
14.4 Expiratory flow amplifier
This block consists of the board PC 1623
EXPIRATORY FLOW AMPLIFIER with its plastic
housing and the expiratory flow connection
cable.
Two potentiometers and a green indicator
LED are used when calibrating the flow
signal according to chapter Calibration in the
Operating Manual.
The change in resistance in the 14.3 EXPIRA-
TORY FLOW TRANSDUCER is converted to a
corresponding signal voltage. This signal, a
non-linear function of the flow, is handled in
the main block 18 EXP. FLOW LINEARIZATION.
A temperature sensor mounted close to the
14.3 EXPIRATORY FLOW TRANSDUCER measures its
temperature. The signal TEMP SENSOR is used
by the TRANSDUCER TEMPERATURE CONTROL block
in the main block 18 EXP. FLOW LINEARIZATION.
The connector (N30) at the end of the
expiratory flow connection cable can be
disconnected from the 18 EXP. FLOW
LINEARIZATION
(PC 1615: N30). Thus an extra
14 EXPIRATORY CHANNEL can be calibrated and
ready for use, but only in the ventilator it has
been calibrated in.
14.5 Expiratory valve tube
This tube connects the 14.3 EXPIRATORY FLOW
TRANSDUCER
with the 14.6 EXPIRATORY OUTLET. It
is mounted on a holder pin and it contains a
fitting which connects via a nipple to the
main block 12 EXPIRATORY PRESSURE. The
EXPIRATORY VALVE TUBE is squeezed between
the metal bars of the 16 EXPIRATORY VALVE.
Service interval 1000 h of operation for
exchange of the EXPIRATORY VALVE TUBE.
14.6 Expiratory outlet with non-
return valve
The gas from the patient system leaves the
ventilator via this outlet. It contains a non-
return valve. Its rubber membrane is
mounted on a valve seat disc which can be
removed from the expiratory outlet.