Datex-Ohmeda S-5 Service Manual S5 Airway

S/5

Datex-Ohmeda

S/5TM Airway Module, G-AO (rev. 06)

TM

S/5

S/5

S/5

TM

Airway Module, G-AiO (rev. 05)

TM

Airway Module, G-AiOV (rev. 04)

TM

Airway Module, G-AOV (rev. 04)

Gas Interface Board, B-GAS (rev. 01)

Technical Reference Manual Slot

Datex-Ohmeda Inc.
3030 Ohmeda Drive
53707-7550 MADISON, WIS
USA
Tel. [phone], Fax [phone]

www.us.datex-ohmeda.com

All specifications are subject to change without notice.

Document No. 800 1005-1

June 2001

Datex-Ohmeda Division,

Instrumentarium Corp.

P.O. Box 900, FIN-00031

DATEX-OHMEDA, FINLAND

Tel. [phone] Fax [phone]

www.datex-ohmeda.com

 Instrumentarium Corp. All rights reserved.

Table of contents

TABLE OF CONTENTS

S/5 Airway modules and S/5 Gas Interface Board, B-GAS

TABLE OF CONTENTS i
TABLE OF FIGURES iii
INTRODUCTION 1
1 Specifications 2

1.1 General specifications..............................................................................................................................2

1.2 Typical performance.................................................................................................................................2

1.2.1 CO

1.2.2 Respiration rate................................................................................................................................2

1.2.3 O

1.2.4 N

1.2.5 Hal, Iso, Enf......................................................................................................................................2

1.2.6 Sev..................................................................................................................................................2

1.2.7 Des..................................................................................................................................................3

1.2.8 Agent identification..........................................................................................................................3

1.2.9 Patient Spirometry............................................................................................................................3

1.2.10 Airway Pressure (Paw)...................................................................................................................3

1.2.11 Tidal Volume (TV)..........................................................................................................................3

1.2.12 Minute Volume (MV).....................................................................................................................3

1.2.13 Airway flow...................................................................................................................................3

1.3 Technical specification .............................................................................................................................4

1.3.1 CO

1.3.2 O

1.3.3 N

1.3.4 AA...................................................................................................................................................4

..................................................................................................................................................2

2

....................................................................................................................................................2

2

O .................................................................................................................................................2

2

..................................................................................................................................................4

2

....................................................................................................................................................4

2

O .................................................................................................................................................4

2

2 Functional Description 5

2.1 Measurement principle.............................................................................................................................5

2.1.1 CO

2.1.2 O

2.1.3 Agent identification..........................................................................................................................7

2.1.4 Patient Spirometry............................................................................................................................ 8

2.2 Main components.....................................................................................................................................9

2.2.1 Gas sampling system......................................................................................................................10

2.2.2 ACX-200 measuring unit.................................................................................................................16

2.2.3 OM measuring unit.........................................................................................................................17

2.2.4 ACX measuring board.....................................................................................................................18

2.2.5 ASX agent identification bench........................................................................................................20

2.2.6 ASX measuring board.....................................................................................................................20

2.2.7 PVX board......................................................................................................................................22

2.2.8 Gas mother boar d...........................................................................................................................24

2.2.9 Gas interface board........................................................................................................................26

2.3 Connectors and signals...........................................................................................................................26

2.3.1 Module bus connector....................................................................................................................26

, N2O and Agent measurement....................................................................................................5

2

measurement..............................................................................................................................6

2

Document No. 800 1005-1

i

Datex-Ohmeda S/5 Anesthesia Monitor

2.3.2 Gas mother board connectors.........................................................................................................27

3 Service Procedures 31

3.1 General service information....................................................................................................................31

3.2 Service check.........................................................................................................................................32

3.2.1 Recommended tools......................................................................................................................32

3.2.2 Recommended parts......................................................................................................................32

3.3 Disassembly and reassembly..................................................................................................................41

3.4 Adjustments and calibrations..................................................................................................................42

3.4.1 Gas sampling system adjustment...................................................................................................42

3.4.2 Flow rate measurement..................................................................................................................42

3.4.3 Oxygen measurement unit adjust ments...........................................................................................44

3.4.4 Flow calibration..............................................................................................................................46

4 Troubleshooting 47

4.1 Troubleshooting chart.............................................................................................................................47

4.1.1 Supply voltage troubleshooting.......................................................................................................48

4.2 Gas sampling system troubleshooting.....................................................................................................49

4.2.1 Sampling system leak test..............................................................................................................49

4.2.2 Water separation............................................................................................................................49

4.2.3 Steam test for the special tubes......................................................................................................49

4.3 OM measuring unit troubleshooting.........................................................................................................50

4.4 ACX troubleshooting...............................................................................................................................50

4.4.1 Cleaning the measuring chamber of ACX measuring unit..................................................................50

4.5 ASX agent identification unit troubleshooting...........................................................................................52

4.6 PVX board troubleshooting......................................................................................................................53

4.7 Gas mother board troubleshooting..........................................................................................................53

4.7.1 Instru ctions after replacing the software or Gas mother board...........................................................53

4.8 Error messages.......................................................................................................................................54

5Service menu 55

5.1 Gas mother board...................................................................................................................................56

5.2 ACX service menu...................................................................................................................................59

5.3 PVX service menu...................................................................................................................................61

5.3.1 Flow calibration..............................................................................................................................62

5.3.2 Temp & Hum service menu.............................................................................................................63

5.4 ASX service menu...................................................................................................................................64

6 Spare parts 65

6.1 Spare parts list.......................................................................................................................................65

6.1.1 G-AO rev. 01, G-A iO rev. 00............................................................................................................65

6.1.2 G-AO rev. 02, G-A iO rev. 01, G-AOV rev. 00, G-AiOV rev. 00.............................................................66

6.1.3 G-AO rev. 03, G-A iO rev. 02, G-AOV rev. 01, G-AiOV rev. 01.............................................................66

6.1.4 G-AO rev. 04, G-A iO rev. 03, G-AOV rev. 02, G-AiOV rev. 02, G-O rev. 00, G-OV rev. 00.....................67

6.1.5 G-AO rev. 05, G-A iO rev. 04, G-AOV rev. 03, G-AiOV rev. 03, G-O rev. 01, G-OV rev. 01.....................67

6.1.6 S/5 G-AO rev. 06, G-A iO rev. 05, G-AOV rev. 04, G-AiOV rev. 04......................................................67

6.1.7 Panel stickers................................................................................................................................67

6.1.8 S/5 panel stickers.........................................................................................................................68

6.1.9 Planned Maintenance (PM) Kits:.....................................................................................................69

6.1.10 Gas Interface Board, B-GAS.......................................................................................................69

7 Earlier Revisions 70

ii

Document No. 800 1005-1

Table of contents

APPENDIX A

71

Service check FORM A-1

TABLE OF FIGURES

Figure 1 CO2/N2O/AA gas absorption spectra.....................................................................................................5

Figure 2 O

Figure 3 Anaesthetic Agents gas absorption spectra............................................................................................7

Figure 4 Airway module block diagram...............................................................................................................9

Figure 5 Gas sampling system block diagram ...................................................................................................12

Figure 6 Gas sampling system layout................................................................................................................13

Figure 7 Gas sampling system block diagram ...................................................................................................13

Figure 8 Gas sampling system layout................................................................................................................14

Figure 9 ACX photometer (ACX-200 measuring unit)..........................................................................................16

Figure 10 CO

Figure 11 ACX measuring board block diagram...............................................................................................19

measurement principle....................................................................................................................6

2

O/AA measurement block diagram......................................................................................17

2/N2

Figure 12 ASX measuring unit ........................................................................................................................20

Figure 13 ASX measuring board block diagram...............................................................................................21

Figure 14 PVX board block diagram................................................................................................................23

Figure 15 Gas mother board block diagram....................................................................................................25

Figure 16 Gas sampling system adjustment chart...........................................................................................43

Figure 17 O

measuring unit adjustments.......................................................................................................46

2

Figure 18 ASX troubleshooting flowchart.........................................................................................................52

Figure 19 PVX board troubleshooting flowchart...............................................................................................53

Document No. 800 1005-1

iii

Datex-Ohmeda S/5 Anesthesia Monitor

iv

Document No. 800 1005-1

INTRODUCTION

The S/5 Airway Modules, G-AO, G-AiO, G-AOV and G-AiOV are designed for use with the S/5
Anesthesia Monitor and provide airway and respiratory parameters. Later in this manual modules
can be called w/o system name S/5.

This Technical Reference Manual Slot provides information for the maintenance and service of the
airway modules. Please see also related
system e.g. related documentation, conventions used, symbols on equipment, safety precautions,
system description, system installation, interfacing, functional check and planned maintenance.

Letters in the name stand for:
G = Side mountable gas module
O = CO
V = Patient Spirometry
A = Anesthetic agents
i = Agent identification

, Patient O2, and N2O

2

Technical Reference Manual

S/5 Airway modules

for information related to

Table 1 Options of Parameter Modules

G-AO
G-AiO
G-AOV
G-AiOV

NOTE: The Airway Modules and Compact Airway Modules cannot be used simultaneously in the
same monitor.

Gas Interface Board

Gas Interface Board, B-GAS is used for connecting the airway module to the central unit. The
connection can also be made through the Interface Board, B-INT.

CO

N2O Patient O

2

•• • •

•• • • •

•• • • •

•• • • • •

Agents Agent id Spirometry

2

Document No. 800 1005-1

1

Datex-Ohmeda S/5 Anesthesia Monitor

1 SPECIFICATIONS

1.1 General specifications

Module size, W × D × H 135 × 410 × 135 mm/5.3 × 15.0 × 5.3 in
Module weight 6 kg/13 lbs.

1.2 Typical performance

Sampling rate 200 ml/min nominal (180...220 ml/min)
Display update rate breath-by-breath

Automatic compensation for pressure, CO
Warm-up time 3 min for operation, 30 min for full specifications.

Auto-zeroing is performed at start-up, after 5 min + 5 min + 5 min + 15 min + 15 min + 15 min,
and after that every 60 min at regular intervals.

1.2.1 CO

2

Measurement range 0 to 10 %, (0 to 10 kPa), (0 to 76 mmHg)
Extended range 10 to 15 %, (10 to 15 kPa), (76 to 114 mmHg) (unspecified)

concentration is below 0.1 %, 0.0 % is displayed.

If CO

2

1.2.2 Respiration rate

Breath detection 1 % change in CO2 level
Measurement range 4 to 60 breaths/min

1.2.3 O

2

Measurement range 0 to 100 % O

1.2.4 N2O

O, and CO2-O2 collision broadening effect.

2-N2

2

Measurement range 0 to 100 % N2O

1.2.5 Hal, Iso, Enf

Measurement range 0 to 5 %
Extended range 5 to 15 % (unspecified)

1.2.6 Sev

Measurement range 0 to 8 %
Extended range 8 to 15 % (unspecified)

2

Document No. 800 1005-1

1.2.7 Des

Measurement range 0 to 18 %
Extended range 18 to 30 % (unspecified)

Resolution two decimals when the AA concentration below 1.0 %
If AA concentration is below 0.10 %, 0.00 % is displayed.

1.2.8 Agent identification

Identified agents HAL, ENF, ISO, SEV, DES
Identification time 30 seconds (typical value with pure agents)
Identification threshold 0.15 vol% (typical)

Mixture warning when minor component concentration > 0.3 vol% and > 15 %of total agent
concentration

1.2.9 Patient Spirometry

Values are valid when:
Respiratory rate adult 4...30 pedi 4...50 breaths/min
I:E ratio 1:3 - 1:0.5
Inner diameter of ET tube is ≥ 5.5 mm (adult) or 3 to 6 mm (pediatric).

S/5 Airway modules

1.2.10 Airway Pressure (Paw)

Accuracy ±1.5 cmH2O
Resolution 1 cmH
Measuring range -20 to +80 cmH

1.2.11 Tidal Volume (TV)

Accuracy ±6 % or 30 ml (adult); ±6 % or 4 ml (ped)
Resolution 1 ml
Measurement range 150 to 2000 ml (adult)

1.2.12 Minute Volume (MV)

Resolution 0.1 l/min
Measurement range 2 to 15 l/min (adult)

1.2.13 Airway flow

Measurement range 1.5 to 100 l/min for both directions (adult)

O

2

O

2

15 to 300 ml (ped)

0.5 to 5 l/min (ped)

0.25 to 25 l/min for both directions (ped)

Document No. 800 1005-1

3

Datex-Ohmeda S/5 Anesthesia Monitor

1.3 Technical specification

1.3.1 CO

1.3.2 O

2

1.3.3 N2O

2

Measurement rise time <360 ms (from 10 to 90 %)
Gain stability ≤0.2 %CO

≤0.4 %CO

Gain temperature drift ≤0.2 %CO

≤0.4 %CO

Nonlinearity error ≤0.2 %CO

≤0.4 %CO

/24 h (0 to 8 %)

2

/24 h (8 to 10 %)

2

/10 °C (0 to 8 %)

2

/10 °C (8 to 10 %)

2

(0 to 8 %)

2

(8 to 10 %)

2

Measurement rise time <480 ms (from 10 to 90 %)
Gain drift ≤2 % O
Gain temperature drift ≤3 % O
Nonlinearity error ≤2 % O

/24 h

2

/10 °C

2
2

Measurement rise time <360 ms (from 10 to 90 %)
Gain drift ≤2 % N
Gain temperature drift ≤3 % N
Nonlinearity error ≤2 % N

O/24 h

2

O/10 °C

2

O

2

1.3.4 AA

Measurement rise time <520 ms (from 10 to 90 %)
Gain drift ≤0.4 % AA/24 h
Gain temperature drift ≤0.4 % AA/10 °C
Nonlinearity error ≤0.2 % AA

Protection against electrical shock

Type BF

4

Document No. 800 1005-1

2 FUNCTIONAL DESCRIPTION

2.1 Measurement principle

2.1.1 CO2, N2O and Agent measurement

The CO2, N2O, and anesthetic agent gas measurements are based on absorption of infrared light as
it passes through the gas sample in measuring chamber in the photometer. The light absorption is
measured at three wavelengths using an infrared detector. One of the wavelengths is that of the

absorption peak at 4.3 micrometers, the second is that of the N2O absorption peak at 3.9

CO

2

micrometers, and the third is that of the anesthetic agent absorption peak at 3.3 micrometers. The
signal processing electronics receive the signals from the IR detector and demodulate it to get DC
components out of these signals which correspond to the content of each gas in the sample.

S/5 Airway modules

Figure 1 CO2/N2O/AA gas absorption spectra

5

Document No. 800 1005-1

Datex-Ohmeda S/5 Anesthesia Monitor

2.1.2 O2 measurement

The differential oxygen measuring unit uses the paramagnetic principle in a pneumatic bridge
configuration. The signal picked up with a differential pressure transducer is generated in a
measuring cell with a strong magnetic field that is switched on and off at a frequency of 110 Hz.
The output signal is a DC voltage proportional to the O
gases to be measured.

Microphone

2

Electromagnet

concentration difference between the two

Mixture
out

Switched
magnetic
field

Sample in

Reference in

Figure 2 O2 measurement principle

6

Document No. 800 1005-1

2.1.3 Agent identification

The anesthetic agent identification bench identifies Halothane, Enflurane, Isoflurane, Desflurane
and Sevoflurane.

The bench measures the spectrum of the gas between 3.24 µm and 3.39 µm. Because the
spectrum of each of the anaesthetic agents is different it is possible to identify them.

The bench consists of an infrared source, a measuring chamber, a rotating filter and a detector. The
peak wavelength of the narrow bandpass filter changes when the angle between the light path and
the filter is changed. When the filter rotates the required spectrum is scanned through. The agent or
a mixture of agents is identified by comparing the measured spectrum with stored reference
spectra.

500
450
400
350
300
250
200
150
100

50

0

S/5 Airway modules

Anesthetic Agent Gas Absorption Spectra

Halothane 0
Enflurane 0
Isoflurane 0
Sevoflurane 0
Desflurane 0
Freon 0

3246

3306

Wavelength [nm]

Figure 3 Anaesthetic Agents gas absorption spectra

3386

Document No. 800 1005-1

7

Datex-Ohmeda S/5 Anesthesia Monitor

2.1.4 Patient Spirometry

In anesthesia, CMV (Controlled Mechanical Ventilation) is the mostly used ventilation mode. In this
mode, mechanical breaths are delivered to the patient by a ventilator with a proper tidal volume
(TV), respiration rate (RR), and inspiration/expiration ratio in time (I:E) determined by the settings of
the ventilator.

Delivery of life support gases is based on pressure. However, without knowing volume measured of
exhalation, one cannot be sure that a breath occurred. The ultimate goal of ventilation is to use the
least amount of pressure to generate the most appropriate volume for each breath.

The Patient Spirometry monitors ventilation in anesthesia. Both patient breathing circuit and the
function of the ventilator are monitored. The following parameters are displayed:

Expiratory and inspiratory tidal volume (TV) in ml.
Expiratory and inspiratory minute volume (MV) in l/min.
Expiratory volume in first second (V1.0) in per cent for adults and in 0.5 seconds for children.
Inspiration/expiration ratio in time (I:E)
Airway pressures: Peak pressure (P
pressure (PEEP), Real time airway pressure waveform (P
Flow: Real time flow waveform (V')
Compliance (C)
Pressure volume loop
Flow volume loop

), End inspiratory pressure (P

peak

)

aw

), Positive end expiratory

plat

Airway pressure

Airway flow

PEEP, P

peak

, and P

are measured by pressure transducer on the PVX board. Atmospheric pressure

plat

is used as a reference in measurement. The pressure measurement is made from the airway part
that is closest to the patient between patient circuit and intubation tube.

The measurement is based on measuring the kinetic gas pressure and is performed using Pitot
effect. Pressure transducer is used to measure the Pitot pressure. The obtained pressure signal is
linearized and corrected according to the density of the gas. Speed of the flow is calculated from
these pressure values and TV value is then integrated. MV value is further calculated a nd averaged
using TV and RR (respiratory rate) values.

8

Document No. 800 1005-1

Patient Spirometry sensor, D-lite

Patient Spirometry is measured with a specific sensor, D-lite or Pedi-lite.
D-lite and Pedi-lite sensors are designed to measure kinetic pressure by t wo-sided Pitot tube. The

pressure reduction caused by measuring cross is taken into account, too, especially in small flows.
Velocity is calculated from pressure difference according to Bernoulli's equation. Flow is then

determined using the calcula ted velocity.

2dP×

v=

ρ

S/5 Airway modules

(from Bernoulli's equation)

F=v A×

,

where,
F=flow (l/min)
v=velocity (m/s)
A=cross area (m
dP=pressure difference (cmH

ρ=density (kg/m

Finally the volume information is obtained by integrating the flow signal.

2.2 Main components

The airway modules consist of ACX-200 and OM-101 gas measuring units, ASX-200 agent
identification unit (G-AiO/AiOV), PVX board (G-OV/AiOV/AOV), gas sampling system, ACX
measuring board and gas mother board.

Oxygen
Measuing
Unit

Serial I/O

X4

Supply
voltages

+5 V, GND

X1

Serial I/O

2

)

3

)

O2
signal

ACX
Board

2

Signal out

Supply
voltages,
Control

ACX

Supply

serial

voltages

I/O

Gas Module CPU

O)

ACX
Bench

X1
X2

Valve
controls

ACX, ASX,
PVX serial
I/O

+5 Vref

X8

+5 VL
GND

GNDD

Lamp
Supply
Voltage

Lamp
Driver

Lamp
control

Pump control
Mod key in

X9

Lamp
control

ASX
Unit

Supply
voltages

ASX
serial
i/O

Valve controls

+15 VD, GNDD

Pump control

+15 VD, GNDD

PVX
Board

X5

Supply
voltages

PVX
serial
i/O

Valve
Driver

Pump
Driver

X1
X3

Gas pressure
and flow in

X10

+24/+32 VD

X12

+15 VD

X7

+15 VD

Fan

Valves

Pump

+5 V
+5 VL
+15 VD
+/-15 V
+24 /+32 VD
GND
GNDD

+15 V

Regulator

Figure 4 Airway module block diagram

Gas Mother Board

GND

Mod key in

X11

Module
Key

Document No. 800 1005-1

9

Datex-Ohmeda S/5 Anesthesia Monitor

2.2.1 Gas sampling system

The gas sampling system samples the measured air to the module, and removes water and
impurities from it. A sampling line is connected to the water trap on the front panel. The pump
draws gas through the sampling line to gas measuring units. After the measurements, the gas is
exhausted from sample gas out connector on the rear panel of the module.

Water trap, D-fend

The gas sample enters the monitor through the water trap, where it is divided into two flows, main
flow and side flow (see Gas sampling system block diagram). The main flow goes into the
measuring system through a hydrophobic filter.

The side flow creates a slight sub-atmospheric pressure within the water trap container. This
facilitates gathering th e fluid removed by the hydrophobic filter.

Sampling line

The sampling line is an integral part of the total sampling system. The resistance established by the
sampling line is significant when the software determines the occlusion a nd air-leak alarm limits
during the turn-on sequence.

The Nafion

Zero valve

The small inner diameter causes fluids such as blood or mucus not to propagate within the tube, so
that when the line is clogged, it is replaced.

TM

tube

1)

A nafion tube (tubes A or B, and C: see figure 5) is used to balance the sample gas humidity with
that of ambient air. The tube will prevent errors caused by the effect of water vapor on gas partial
pressure when humid gases are measured after calibration with dry gases. It is inserted between
the water trap and the zero valve (G-AiO/A iOV) or between the zero valve and ACX-200 measuring
unit (G-O/OV/AO/AOV). The tube is also inserted between the CO

absorber and the zero valve.

2

The main flow passes through a solenoid valve before proceeding to the ACX-200 measuring unit.
This valve is activated to establish the zero points for the A CX-200 and O

measuring units at start-

2

up, at 5 minutes, and after that at regular intervals. After 1-hour monitoring, the auto-zeroing is
performed once an hour. When the valve is activated, room air is drawn through the CO
into the internal system and the gas sensors.

absorber

2

1)

10

Document No. 800 1005-1

Nafion is a trademark of Du Pont

Gas measuring units, ACX-200 and O2 unit

After the zero valve, the gas passes through the ACX-200 and O2 measuring units. In the ACX-200
measuring unit, infrared light is passed through chambers containing the main flow gas
(measurement) and a chamber containing reference gas. The measurement is made by
determining the ratio between the two light intensities.

The oxygen sensor has two inputs. One input accepts the main flow and the other draws in room air
for reference. The sensor uses a differential pressure transducer to compare the pressure gradient
produced when both gases are exposed to an oscillating magnetic field. Both gas flows exit from a
single port.

In i model, the ASX agent identification unit is installed in parallel with the oxygen sensor . The task
of the ASX unit is to identify anesthesia agents by infrared light method used also in the ACX-200
unit.

Pressure valve

The pressure valve is used to meas ure the pressure gradient between the O2 measurement flow
and the O
filter.

reference flow. This pressure gradient reflects the condition of the D-fend water trap

2

S/5 Airway modules

Normally the pressure gradient between the O
approximately +8 mmHg. If the software detects the gradient to be between 0 and -5 mmHg, the
pressure valve will initiate pressure measurement of the reference flo w. If the gradient is greater
than -5 mmHg, the software triggers the message ’Replace Trap’.

Flow cassettes

The internal flow rates are set using flow cassettes. These cassettes are used to set the side flow
rate and the O

reference flow rate, the flow rates through the measuring units and the total flow

2

rate of the sampling system.

Sampling pump and damping chamber

The sampling pump is a vibrating membrane pump driven by a 50 Hz/12 V/0.4 A square wave
current.

The damping chamber is used to even out the pulsating flow and silence the exhaust flow.

measurement flow and the reference flow is

2

11

Document No. 800 1005-1

Datex-Ohmeda S/5 Anesthesia Monitor

Figure 5 Gas sampling system block diagram

In G-AO, -AOV models, tube A is Teflon, B and C Nafion. In G-AiO, -AiOV models, tubes A and C are
Nafion, B is Teflon.

See new tubing since autumn 1998 in figure 7.

12

Document No. 800 1005-1

S/5 Airway modules

A

Ref IN
Room AIR

Sample
Gas IN

Figure 6 Gas sampling system layout

See new sampling system layout since autumn 1998 in figure 8.

Filter

CO

2

absorber

Pressure valve

Pressure
transducer

C

ASX-200

in G-AiO/AiOV

Sample pump

Zero valve

main flow

D-fend

B

ACX-200

O2 sensor

Damping
chamber

side flow

Constriction casse tte

Figure 7 Gas sampling system block diagram

In G-AO, -AOV models, tube A is Teflon, B and C Nafion. In G-AiO, -AiOV models, tubes A and C are
Nafion, B is Teflon. Figure 7 is valid for modules manufactured since autumn 1998.

Sample
Gas OUT

13

Document No. 800 1005-1

Datex-Ohmeda S/5 Anesthesia Monitor

Figure 8 Gas sampling system layout

Figure 8 is valid for modules manufactured since autumn 1998.

14

Document No. 800 1005-1

Table 2 Flow cassettes

S/5 Airway modules

Flow

Code

cassette

50/26.0 878048
50/19.0 873800
50/16.3 878047
50/15.3 873801
50/14.1 878046
50/13.1 873802
50/12.4 878045
50/11.2 874770
50/10.4 873803
50/9.2 874509
50/8.7 873804
50/7.4 873805
50/6.5 878044
50/5.8 873806
50/5.1 878043
50/4.4 873807
50/3.8 878042
50/3.2 873808
50/3.0 878040
50/2.8 878039
50/2.5 878038
50/2.3 873809
50/2.0 878037
50/1.8 873810
50/1.6 878036
50/1.4 873811
50/1.1 873812

NOTE: The number on the cassette represents relative flow when a specific pressure is applied.
Therefore 50/26.0 presents the least resistance and 50/1.1 the most.

Document No. 800 1005-1

15

Datex-Ohmeda S/5 Anesthesia Monitor

2.2.2 ACX-200 measuring unit

The ACX photometer is of dual path type. The infrared light beam passes through a measuring
chamber containing the gas to be analyzed, and a reference chamber, which is free of CO
and AA. The measurement is made by determining the ratio between the two light intensities.

, N2O,

2

Figure 9 ACX photometer (ACX-200 measuring unit)

A filter wheel is used to control the light from an incandescent lamp that passes through the
photometer. The filters are arranged so that the light is passed sequentially:

• first at the CO

• then through the measuring chamber

• finally it is blocked completely

The same sequence is repeated at the N

absorption wavelength through the reference chamber

2

O and anaesthetic agent gas absorption wavelengths.

2

After passing through the filters the light is reflected and focused by a mirror onto the infrared
detector. This detector measures the three light levels for each gas described above.

There is an optical sensor incorporated in the photometer which detects light from a reflective
surface on the filter wheel once every revolution. The pu lses from this sensor are us ed to
synchronize the electronics to the signal from the infrared detector. A stabilizing diode measures
the temperature, which is needed to compensate for thermal drifts. The infrar ed detector, the
optical sensor and the stabilizing diode are mounted on the preamplifier board.

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Figure 10 CO2/N2O/AA measurement block diagram

2.2.3 OM measuring unit

The oxygen measurement is based on the paramagnetic susceptibility, which is a unique property
of oxygen among all gases generally present in a breathing gas mixture. The gas to be measured
and the reference gas, which usually is room air, are conducted into a gap in an electromagnet with
a strong magnetic field switched on and off at a frequency of approximately 110 Hz.

An alternating differential pressure is generated between the sample and reference inputs due to
forces acting to the oxygen molecules in a magnetic field gradient.

The pressure is measured with a sensitive differential transducer, rectified with a synchronous
detector and amplified to produce a DC voltage proportional to the oxygen partial pressure
difference of the two gases.

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2.2.4 ACX measuring board

The measuring electronics can be divided into a few functional blocks, which are described below
(see the block diagram in figure 11).

The ACX Measuring board controls gas measurements. It converts the photometer signal into digital
data, calculates results and transmits it to Gas mother board. The board contains, in addition to
the 80C51FA processor, EPROM, RAM, and EEPROM, several analog and digital I/O functions.

Internal and external bus

The processor has access to the Measuring board peripherals (memory, A/D converter, D/A
converters, etc) via an internal bus. For communication between the Gas mother board and the
Measuring board, there is an external bus in connector X1.

Memory

Memory components include 64k × 8 bit EPROM program memory, 32k × 8 bit low current CMOS
RAM, and EEPROM for permanent calibration values and setup memory.

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Figure 11 ACX measuring board block diagram

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