Service manual

2
Servo Ventilator 300/300A Description of functions
E382 E380E 061 01 03 01 Siemens-Elema AB 75
18.4 Expiratory flow linearizer
Analog linearizing circuit using the unlinear
flow signal from the 14.4 EXPIRATORY FLOW
AMPLIFIER
generating a linear signal
representing the measured expiratory flow.
This signal is used by the block 18.5 GAS
COMPOSITION
COMPENSATION.
18.5 Gas composition
compensation
The measured expiratory flow signal from
the block 18.4 EXPIRATORY FLOW LINEARIZER is
adjusted for the contents of oxygen and for
the ambient pressure resulting in the output
signal EXP. FLOW. This limited adjustment
function is controlled by the block 18.1
LINEARIZING CPU.
The resulting flow signal is a flow measure-
ment referenced to standard barometric
pressure (1013 mbar, 760 mm Hg). For
conversion to ambient barometric pressure,
see section "Conversion of flow and volume
to get reference to ambient pressure" in the
Operating Manual.
18Expiratory flow
linearization
This main block consists of the board
PC 1615 EXP. FLOW LINEARIZATION . The purpose
of this main block is to linearize the output
signal for expiratory flow.
18.1 Linearizing CPU including
LIN-PROM functions
The LINEARIZING CPU will calculate a
compensation factor for the flow output
signal (EXP. FLOW). This compensation
depends on:
• Gas composition (O
2
concentration)
• Expiratory pressure
• Barometric pressure.
18.2 Transducer temperature
control
The block TRANSDUCER TEMPERATURE CONTROL
uses the temperature signal (TEMP. SENSOR)
from the 14.4 EXPIRATORY FLOW AMPLIFIER to
regulate the temperature in the 14.3
EXPIRATORY FLOW TRANSDUCER by controlling the
current to its heating resistor.
18.3 Zero offset
Automatic zeroing of the unlinear flow signal
from the 14.4 EXPIRATORY FLOW AMPLIFIER is
made every breath when the actual real
expiratory flow is zero (during inspiration
time).