Datex-Ohmeda
S/5TM EEG Module, M-EEG (rev. 01)
TM
S/5
EEG Headbox, N-EEG (rev. 01)
Technical Reference Manual Slot
Datex-Ohmeda Inc.
3030 Ohmeda Drive
53707-7550 MADISON, WIS
USA
Tel. +1-608-221 1551,Fax +1-608-222 9147
www.us.datex-ohmeda.com
All specifications are subject to change without notice.
Document No. 800 1011-1
June 2001
Datex-Ohmeda Division,
Instrumentarium Corp.
P.O. Box 900, FIN-00031
DATEX-OHMEDA, FINLAND
Tel. +358 10 394 11 Fax +358 9 146 3310
www.datex-ohmeda.com
Instrumentarium Corp. All rights reserved.
Table of contents
TABLE OF CONTENTS
EEG Module, M-EEG and EEG Headbox, N-EEG
TABLE OF CONTENTS I
TABLE OF FIGURES II
INTRODUCTION 1
1 SPECIFICATIONS 2
1.1 General specifications ..............................................................................................................................2
1.1.1 Headbox..........................................................................................................................................2
1.1.2 Module............................................................................................................................................2
1.2 Technical specifications............................................................................................................................2
1.2.1 EEG .................................................................................................................................................2
1.2.2 AEP..................................................................................................................................................3
1.2.3 EMG ................................................................................................................................................3
1.2.4 Impedance measurement.................................................................................................................3
2 FUNCTIONAL DESCRIPTION 4
2.1 Measurement principle .............................................................................................................................4
2.1.1 EEG .................................................................................................................................................4
2.1.2 FEMG...............................................................................................................................................4
2.1.3 AEP..................................................................................................................................................4
2.1.4 Impedance measurement.................................................................................................................5
2.2 Main components.....................................................................................................................................5
2.2.1 Neuro board.....................................................................................................................................5
2.2.2 Headbox board.................................................................................................................................6
2.3 Connectors and signals.............................................................................................................................7
2.3.1 Module bus connector......................................................................................................................7
2.3.2 Module front panel connectors..........................................................................................................8
2.3.3 Headbox input connector..................................................................................................................8
3 SERVICE PROCEDURES 9
3.1 General service information.......................................................................................................................9
3.2 Service check .........................................................................................................................................10
3.2.1 Recommended tools ......................................................................................................................10
3.3 Disassembly and reassembly..................................................................................................................14
3.3.1 M-EEG ...........................................................................................................................................14
3.3.2 N-EEG............................................................................................................................................14
4 TROUBLESHOOTING 15
4.1 Troubleshooting chart .............................................................................................................................15
4.2 Troubleshooting flowcharts......................................................................................................................16
5SERVICE MENU 18
5.1 EEG & EP service menu...........................................................................................................................19
6 SPARE PARTS 23
6.1 Spare part list.........................................................................................................................................23
6.1.1 M-EEG rev. 00................................................................................................................................23
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Datex-Ohmeda S/5 monitors
6.1.2 S/5 M-EEG rev. 01.........................................................................................................................23
6.1.3 N-EEG rev. 00 ................................................................................................................................24
6.1.4 S/5 N-EEG rev. 01 .........................................................................................................................24
6.1.5 Front panel stickers ........................................................................................................................25
7 EARLIER REVISIONS 26
APPENDIX A 27
SERVICE CHECK FORM A-1
TABLE OF FIGURES
Figure 1 Measurement setup .............................................................................................................................1
Figure 2 Neuro board block diagram ..................................................................................................................5
Figure 3 Audio stimulator circuitry ...................................................................................................................... 6
Figure 4 EEG headbox board block diagram........................................................................................................6
Figure 5 EEG module troubleshooting flowchart ................................................................................................16
Figure 6 Headbox troubleshooting flowchart .....................................................................................................17
Figure 7 Exploded view of module box and EEG module ....................................................................................23
Figure 8 Exploded view of headbox...................................................................................................................24
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Document No. 800 1011-1
INTRODUCTION
This Technical Reference Manual Slot provides information for the maintenance and service of the
Datex-Ohmeda S/5 EEG Module, M-EEG and Datex-Ohmeda S/5 EEG Headbox, N-EEG. The EEG
module is a single width plug-in module designed for use with the S/5 monitors. Later in this
manual modules can be called w/o system name S/5.
Please see also related Technical Reference Manual for information related to system e.g. related
documentation, conventions used, symbols on equipment, safety precautions, system description,
system installation, interfacing, functional check and planned maintenance.
The EEG module and the EEG headbox together measure:
• electroencephalography (EEG)
• spontaneous facial muscular activity with frontal electromyography (FEMG)
• auditory evoked potentials (AEP)
The EEG Headbox, N-EEG, is responsible for EEG and FEMG signal amplification, filtering and
digitalization and electrode impedance measurement. It is situated close to the patient’s head. The
Headbox has connectors for the EEG leads, either for a referential or a bipolar montage, and for the
AEP stimulation earphones.
S/5 EEG Module, M-EEG and S/5 Headbox, N-EEG
The EEG module M-EEG creates auditory stimulus pulses and takes care of AEP signal processing.
It has one connector for the EEG headbox.
1
2
3
4
5
Figure 1 Measurement setup
(1) EEG module measuring EEG and EP
(2) Module-headbox cable
(3) EEG Headbox
(4) Organizer
(5) Earphones (for AEP measurement only)
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Document No. 800 1011-1
Datex-Ohmeda S/5 monitors
1 SPECIFICATIONS
1.1 General specifications
1.1.1 Headbox
Box size, W × D × H 96 × 170 × 34 mm/3.8 × 6.7 × 1.3 in
Box weight 0.5 kg/1.1 lbs
Power consumption 1.9 W
1.1.2 Module
Module size, W × D × H 37 × 180 × 112 mm/1.5 × 7.1 × 4.4 in
Module weight 0.37 kg/0.8 lbs
Power consumption 3.1 W
1.2 Technical specifications
1.2.1 EEG
Amplification 10 000
Resolution 60 nV
Max amplitude 800 µV
Sampling frequency 100 Hz per channel
Range ±400 µV
Frequency range 0.5...30 Hz
Input impedance 8 MΩ @ 10 Hz
Noise level <0.5 µV rms from 0.5 Hz to 30 Hz
CMRR >100 dB @ 50 Hz
Parameters from power spectrum SEF, MF, relative power in frequency bands
Burst suppression calculated burst-suppression ratio (BSR)
Defibrillation protection 5000V, 360 J
Allowable Input Offset ±300 mV
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1.2.2 AEP
S/5 EEG Module, M-EEG and S/5 Headbox, N-EEG
Amplification 10 000
Resolution 60 nV
Max amplitude 1000 µV
pp
Stimulation
Click (condensating) duration 100 µs
Frequency 1.1...9.1 Hz (1 Hz steps) @ 10 ms measurement
1.1...8.1 Hz (1 Hz steps) @ 100 ms measurement
Intensity 10...90 dB nHL, 10 dB steps
Measurement
Sampling frequency 2400 Hz for MLAEP/ 4800 for BAEP
Frequency range 0.5...1000 Hz
Highpass filter off/10/30/50/75/100/150 Hz
Single average:
Averaged responses 100...2000 stimuli
Moving average:
Gross average 100...2000 stimuli
Update interval after every 100 stimuli (200, when gross average is 2000)
1.2.3 EMG
Amplification 50 000
Resolution 100 nV
Max amplitude 100 µV
Frequency range 60...300 Hz
Amplitude Root Mean Square (RMS)
1.2.4 Impedance measurement
Measurement frequency 75 Hz
Current 10 µA
Range 0...30 kΩ
Resolution 100 Ω
Accuracy ±1k or ±10 % whichever is greater
Measurement time, all leads 3 s
Start of measurement manual/automatic
Leads off detection >3 MΩ, continuous
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Datex-Ohmeda S/5 monitors
2 FUNCTIONAL DESCRIPTION
2.1 Measurement principle
2.1.1 EEG
EEG is differential voltage signal measured from electrodes attached to the patient’s skin. EEG
measures the spontaneous electrical activity of the brain. This electrical activity reflects the state of
the brain.
Electrode connections can be made with two different principles: bipolar or referential montage. In
bipolar montage every channel has two electrodes and the signal is the potential difference
between these two electrodes. In referential montage the referential electrode delivers its potential
to every channel’s minus-input. The signal is the potential difference between this common
reference electrode and the electrode connected to plus input. Purpose of the ground electrode is
to reduce common mode noise. It cannot be used as referential electrode.
2.1.2 FEMG
Bipolar connection
The EEG signal is amplified, antialias filtered, digitised and software filtered. After that the EEG
signal is shown on the screen and various characteristics are calculated out of it. These include
spectrum, rms amplitude, spectral edge frequency, median frequency, burst-suppression ratio and
percentage of total power in four different bands: theta (1...4 Hz), delta (5...9 Hz), alpha (9...13 Hz)
and beta (>13 Hz).
FEMG is electrical signal originating from facial muscles. In the headbox the signal of channel 1 is
divided to two different amplification and filtering paths. One is the EEG path and the other is the
FEMG path. FEMG signal has much broader spectrum than EEG and it overlaps with EEG at low
frequencies. Because of this the rms amplitude of FEMG signal is calculated from band
60...300 Hz. Mains power frequency and its harmonics are digitally filtered away to reject
interference noise from power lines.
Referential connection
2.1.3 AEP
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Document No. 800 1011-1
AEP is an electrical response of the nervous system to external auditory stimulus. It is measured
using same electrodes as in EEG measurement, but the sampling frequency and bandwidth are
different. The electrical signal resulting from one stimulus is weaker than the spontaneous activity
of the brain. To overcome this the stimulus is repeated several times (100...2000), and average of
all responses is calculated. Responses containing big artefacts are removed from the average to
improve the signal to noise ratio.
2.1.4 Impedance measurement
The impedance measurement is done from one channel at a time and the EEG or EP measurement
is stopped during the impedance measurement.
Differences in electrode impedance of the electrodes causes common mode noise coupling to
measured signal. To minimise this the electrode impedance is measured and a warning of
unsatisfactory impedance level is generated when necessary. The impedance of an electrode is
measured by applying a known current through the electrode and measuring the voltage drop over
the electrode. This way the impedance of a single electrode can be resolved instead of a sum
impedance of an electrode pair.
2.2 Main components
2.2.1 Neuro board
S/5 EEG Module, M-EEG and S/5 Headbox, N-EEG
The Neuro board consists of the following functional sections:
• audio stimulator
• microprocessor for stimulation and measurement control, and for counting the
measurement results
• two serial communication drivers
The serial bus speed to monitor is 500 kbps and the bus itself is half duplex, i.e. data can be
transferred to both directions but only one way at a time.
The serial bus speed to the headbox is 500 kbps and the bus is full duplex i.e. data can be
transferred to both directions at the same time.
Module
Keys
CPU
3048
+15 V
Data
RS-422
driver
AEP stimulus
AEP
Stimulator
Module Bus
Power
+15 V
Reset
Data
Power
supply
Patient Isolation 5 kV
Opto
Isolation
±5 V
±12V
EEPROM
RAM
RS485
Driver
To
To
EEG
EEG
Head-
Head-
box
box
Figure 2 Neuro board block diagram
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Document No. 800 1011-1
Datex-Ohmeda S/5 monitors
H83048
CTRL
Figure 3 Audio stimulator circuitry
2.2.2 Headbox board
The Headbox board consists of the following functional sections:
• input protection
• EEG amplifiers and filters
• FEMG amplifier and filter
• current feeding circuitry and amplifiers for impedance measurement
• microprocessor
• serial communication
PWM
Audio level
adjustment
Timing
control
Audio
generator
Earphones
Headbox
RS
422
driver
±5 V
±12V
CPU
3048
A
/
D
+15 V
Data
AEP stimulus
Power
supply
Opto
Isolation kV
Isolation
Headbox
Keys
Figure 4 EEG headbox board block diagram
1 p
EEG
signal
1-4
1-4
AEP
stimulus
Impedance
check
a
t
i
e
n
t
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Document No. 800 1011-1
2.3 Connectors and signals
2.3.1 Module bus connector
S/5 EEG Module, M-EEG and S/5 Headbox, N-EEG
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25
1
14
Table 1 Module bus connector (X1) pin description
Pin No. I/O Signal
1 I RESET_RS485
2 I -15 VDC
3 I +15 VDIRTY
4 I +15 VDC
5 I/O -DATA_RS485
6 I/O DATA_RS485
7 - Ground & Shield
8 I -RESET_RS485
9 I CTSB
10 O RTSB
11 I RXDB
12 O TXDB
13 - Ground & Shield
14 I +32 VDIRTY
15 I GroundDIRTY
16 I CTSC
17 O RTSC
18 I RXDC
19 O TXDC
20 - ON/STANDBY
21 - PWM_ECG
22 - RXDD_RS232
23 - TXDD_RS232
24 I +5 VDC
25 I +5 VDC
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