Datex-Ohmeda 3770, 3775 User manual
3770/3775 Pulse Oximeter
Service Manual
%SpO
2
♥
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2798
♥
2798
Not for continuous monitoring
6050-0004-915
Printed in USA
3770/3775 Pulse Oximeter
Service Manual
Important
This manual is subject to periodic review, update, and revision. Customers are
cautioned to verify that the information in this manual applies to the software and
hardware present in the equipment.
Attention! Consult the accompanying instructions before using this
device.
This device performs as described in this manual, and in accompanying labels
and inserts, when assembled, operated, maintained, and repaired in accordance
with the instructions provided.
This device must be cleaned and checked periodically. Do not use a defective
device. Parts that are broken, missing, plainly worn, distorted, or contaminated
should be replaced immediately. If repair or replacement become necessary,
request service advice from Datex-Ohmeda (information is listed on the back
cover). Do not repair this device or any of its parts other than in accordance with
written instructions provided by Datex-Ohmeda.
The user of this device shall have the sole responsibility for any malfunction that
results from improper use, faulty maintenance, improper repair, unauthorized
service, damage, or alteration by anyone other than Datex-Ohmeda.
The safety, reliability, and performance of this device can be assured only under
the following conditions:
• If it is used according to the accompanying operating instructions.
• If fittings, extensions, readjustments, changes, or repairs are carried out by
agents authorized by Datex-Ohmeda.
• If it is used in buildings having ground equalization wiring that complies with
relevant local standards and regulations.
Trademarks
Datex® and Ohmeda® are the property of Instrumentarium Corp. or its
subsidiaries.
FlexConnect is a trademark of Datex-Ohmeda, Inc.
Cidex is a registered trademark of Johnson & Johnson
Duracell is a trademark of Duracell, Inc.
Eveready is a trademark of Eveready Battery Company, Inc.
Formula 409 is a registered trademark of Clorox Company
Hewlet Packard is a registered trademark of Hewlett-Packard Co.
Kodak is a trademark of Eastman Kodak Company
Panasonic is a trademark of Panasonic Industries, Co.
Rayovac and Renewal are registered trademarks and Reusable Alkaline is a
trademark of Rayovac Corporation
Top Crest is a trademark of Safeway, Inc.
Windex is a registered trademark of The Drackett Company
All other product and company names are the property of their respective owners.
Text revised: May 2000
© 1997, 1999, 2000 Datex-Ohmeda, Inc. All rights reserved.
1/Overview
Related information...........................................................................................................1-1
Technical competence.....................................................................................................1-1
General description.....................................................................................................................................1 -2
Theory of operation.....................................................................................................................................1-2
Calibration............................................................................................................................................1-3
Functional components.............................................................................................................................1 -4
Digital board........................................................................................................................................1-5
80-pin board-to-board connector...................................................................1-5
Analog board.......................................................................................................................................1-6
Specifications..................................................................................................................................................1 -7
Electromagnetic effects.................................................................................................................1-7
Environment..........................................................................................................................1-7
EMC performance..............................................................................................................1-7
International Electrotechnical Commission (IEC) classifications.........................1-7
Compliance with standards.......................................................................................................1-8
Oximeter................................................................................................................................................1-8
Default settings.....................................................................................................................1-8
General......................................................................................................................................1-8
Visual displays and indicators.......................................................................1-8
Dimensions................................................................................................................1-8
Power............................................................................................................................1-9
Circuitry......................................................................................................................1-9
Sensor emitter wavelength ranges..............................................................1-9
(3775 only) Audio indicators...........................................................................1-9
SpO2...........................................................................................................................................1-9
Range............................................................................................................................1-9
Accuracy.....................................................................................................................1-9
Calibration.................................................................................................................1-9
Interfering substances.........................................................................................1-9
(3775 only) Alarm limits....................................................................................1-9
Pulse rate .................................................................................................................................1-9
Range............................................................................................................................1-9
Accuracy.....................................................................................................................1-9
Environmental................................................................................................................... 1-10
Operating................................................................................................................ 1-10
Storage...................................................................................................................... 1-10
Battery packs.................................................................................................................................... 1-10
AA battery pack ................................................................................................................ 1-10
Recommended brands.................................................................................... 1-11
NiCd rechargeable battery pack............................................................................. 1-11
Environmental—NiCd and AA................................................................................. 1-11
Operating................................................................................................................ 1-11
Storage...................................................................................................................... 1-11
Precautions....................................................................................................................................................1-12
Warnings............................................................................................................................................ 1-12
Handling............................................................................................................................... 1-12
Failure of operation........................................................................................................ 1-12
Explosion hazard.............................................................................................................. 1-12
Fire hazard.......................................................................................................................... 1-12
Contents
i
Contents
2/ Troubleshooting
3/Service Policy and Repair Procedures
Electrical shock and flammability hazard ........................................................ 1-12
Electrical shock hazard ................................................................................................ 1-13
Patient safety....................................................................................................................... 1-13
Operator safety.................................................................................................................. 1-13
Sensors................................................................................................................................... 1-13
Data validity........................................................................................................................ 1-13
Cautions.............................................................................................................................................. 1-14
Static sensitivity................................................................................................................ 1-14
Battery packs....................................................................................................................... 1-14
Cleaning................................................................................................................................ 1-14
HP printer............................................................................................................................ 1-14
Disposal.................................................................................................................................. 1-14
3770/3775 pulse oximeter.....................................................................................................................2-2
Printer..................................................................................................................................................................2-5
Battery charger monitoring station.....................................................................................................2-6
Battery charger (single)..............................................................................................................................2 -8
Service policy..................................................................................................................................................3 -1
Ordering parts and obtaining service..................................................................................3-1
Packaging and returning equipment....................................................................................3-2
Safety guidelines...........................................................................................................................................3 -2
Cleaning procedures...................................................................................................................................3 -3
Oximeter, battery packs, and battery chargers ...............................................................3-3
Sensors....................................................................................................................................................3-3
Inspecting the oximeter and replacing parts...............................................................................3-4
Disassembling the oximeter .......................................................................................................3-4
Replacing parts..................................................................................................................................3-5
Assembling the oximeter .............................................................................................................3-5
Checking normal operation....................................................................................................................3-7
4/Illustrated Parts
Service kits—3770 and 3775 oximeters.........................................................................................4-1
3775 oximeter assembly..........................................................................................................................4 -2
3775 assembly parts........................................................................................................................4-2
3775 assembly illustration...........................................................................................................4-3
3770 oximeter assembly..........................................................................................................................4 -4
3770 assembly parts........................................................................................................................4-4
3770 assembly illustration...........................................................................................................4-5
ii
1/Overview
This manual contains instructions for servicing the Datex-Ohmeda 3770 and 3775
Pulse Oximeters.
This chapter contains:
• A general description of the oximeter and its functional components.
• Oximeter and battery pack specifications.
• Precautions, including specific warnings and cautions, you must follow when
Related information
The content of this manual assumes you are familiar with how the unit operates.
For a detailed description of the unit’s components, key functions, and general
operating guidelines, see the Datex-Ohmeda 3770/3775P Pulse Oximeter User’s
Manual. General maintenance procedures contained in that manual, such as how
to replace batteries in the AA battery pack, are not repeated in this manual.
If you need to reference printed circuit board schematics and component lists,
purchase and refer to the information contained in the 3770/3775 PCA Drawings
Service Kit, REF 6050-0005-558.
You’ll find detailed instructions for servicing and repairing the battery charger
monitoring station in the Battery Charger Monitoring Station Service Manual (REF
6050-0003-861). If you need to replace fuses or change the voltage selection for the
monitoring station, refer to that manual.
servicing the oximeter.
Note: The NiCd and AA battery packs, the single-station battery charger, and the
Hewlett-Packard® (HP) printer are not serviceable accessories.
For information on sensor application and cleaning (reusable sensors only), see the
instructions for the sensor.
Technical competence
CAUTION: Only qualified service personnel should perform the procedures described in this manual.
Only Datex-Ohmeda service personnel or competent individuals who are
experienced with servicing medical devices of this nature should perform the
procedures described in this manual.
1-1
3770/3775 Pulse Oximeter Service Manual
General description
Two models of the oximeter are available: the 3770 and the 3775. Both oximeters
operate on power supplied by a battery pack. In addition, either oximeter, when a
nickel-cadmium (NiCd) battery pack is attached, can be positioned in the battery
charger monitoring station and operated using the station’s DC (from AC mains)
power supply.
• The 3770 oximeter is designed specifically for spot checking SpO
rate. It has no alarms or user-definable parameters and is not intended for
continuous monitoring.
• The 3775 oximeter is a full-featured model designed for spot checking in
addition to short- and long-term continuous SpO2 and pulse rate monitoring.
This model can print trend data, through an infrared link, to the optional
Hewlett-Packard® (HP) printer.
Note: Throughout this manual, components and features available on both
oximeter models and those found only on the 3775 oximeter are discussed. If you
are working on the 3770, references to components specific to the 3775 do not
apply.
Theory of operation
The oximeter uses a two-wavelength pulsatile system—red and infrared light—to
distinguish between oxygenated (O2Hb) and reduced (HHb) hemoglobin, each of
which absorbs different amounts of light emitted from the oximeter sensor. The
system then calculates the relative percentage of these two constituents and SpO2.
Variable absorption
(Due to arterial pulse)
Arterial blood absorption
Venous blood absorption
and pulse
2
1-2
Absorption
Other tissue absorption
Figure 1-1. Signal composite
Arterial blood pulsation at the test site modulates the transmission of the oximeter
sensor’s light. Since other fluids and tissues present generally don’t pulsate, they
don’t modulate the light passing through that location. The pulsatile portion of the
incoming signal is used to detect and isolate the reduction of light energy due to
arterial blood flow.
Time
1/Overview
1
(Red)
660 nm
)
0
x
Extinction (10
-1
-2
600 700 800 900 1000
Wavelength (nm)
Figure 1-2. Extinction vs. wavelength
The sensor’s photodetector converts the light, which is partially absorbed and
modulated as it passes through the tissue sample, into an electronic signal. Since
O2Hb and HHb allow different amounts of light to reach the photodetector at the
selected wavelengths, the electronic signal varies according to the light source that
is “on” and the oxygenation of the arterial hemoglobin. Analog and digital signal
processing then convert the light-intensity information into SpO2 and pulse rate
values for display on the monitor.
(Infrared)
940 nm
O2Hb
HHb
Calibration
Datex-Ohmeda pulse oximeters use two wavelength ranges, 650 nm to 665 nm and
930 nm to 950 nm, both with an average power of less than 1 mW. These wavelengths
are used to calculate the presence of oxyhemoglobin (O2Hb) and reduced hemoglobin
(HHb). A CO-oximeter typically uses four or more wavelengths of light and calculates
reduced hemoglobin (HHb), oxyhemoglobin (O2Hb), carboxyhemoglobin (COHb), and
methemoglobin (MetHb). Because of this, pulse oximetry readings and CO-oximetry
readings will differ in situations where a patient’s COHb or MetHb are increased.
Two different methods of calibration are currently used by oximeter manufacturers:
fractional and functional.
• The fractional saturation is determined by dividing the oxyhemoglobin by the
total hemoglobin, represented mathematically as
Fractional SpO2 = x 100 = x 100
O2Hb
Hb
TOTAL
O2Hb + HHb + COHb + MetHb
O2Hb
i.e., the percentage of the total amount of hemoglobin carrying oxygen.
• The functional saturation is represented mathematically as
Functional SpO2 = x 100 = x 100
Hb
O2Hb
- COHb - MetHb O2Hb + HHb
TOTAL
O2Hb
i.e., the percentage of hemoglobin capable of carrying oxygen that is carrying
oxygen.
1-3
3770/3775 Pulse Oximeter Service Manual
The calculation of SpO2 assumes 1.6% carboxyhemoglobin (COHb), 0.4%
methemoglobin (MetHb), and no other pigments. Appreciable variation from
these values will influence SpO2 accuracy. These values are based on the DatexOhmeda Pulse Oximeter Empirical Calibration Study.
The 3700/3775 uses the fractional calibration method.
Functional components
Figure 1-3 illustrates the relationship between each functional component.
Battery pack/
AC adapter
Power
Return
Temperature
Battery monitor
board
Analog boardDigital board
Power supplyOn/Off
Signal pathDigital core
Figure 1-3. System block diagram
A complete oximetry system requires digital and analog processing. The digital
board provides signal acquisition, numerical processing, and user interface for the
oximeter. The analog board amplifies and conditions the biological signal. The
digital board then samples the conditioned signal, performs the oximetry
algorithm, and displays the results on numeric and graphic LED displays.
The user interface features an eight-character dot-addressable LED display, a
24-segment LED driver, a variable frequency audio driver, and (for the printer
option) an infrared wireless transmitter.
Sensor
1-4
Digital board
1/Overview
The core processing of the digital board is provided by a 16-bit processor,
nonvolatile FLASH memory, semivolatile SRAM, and a Real Time Clock. For
signal acquisition, it has an A-to-D converter (which is internal to the processor),
I/O ports for timing and control, and an 8-bit D-to-A converter.
On/Off
Power control
(Reset control)
Ambient light
detection
Rotary encoder
and
pushbuttons
Code memory
Data memory
Address
decode
Processor
Analog
Signal
Path
Timing
Analog board
80-pin
connector
Programmable
interval
timer (PIT)
Real-time
clock
Alphanumeric
LED display
LED driver
(bargraph, low
battery, alarm bar)
Peripheral
I/O (PPI)
Audio tone
generator
I.R.
wireless
transmitter
Digital-to-analog
converter (DAC)
Figure 1-4. Digital system block diagram.
80-pin board-to-board connector
The 80-pin board-to-board connector interfaces with the analog board and contains
signals shared by both boards: power supplies, rotary encoder signals, oximetry
timing and control, and many ground connections.
1-5
3770/3775 Pulse Oximeter Service Manual
Analog board
The analog board provides the oximetry analog signal processing, sensor LED
drive, detection of interfering signals, housekeeping and fault monitoring, standby
and operational power, power switching, and battery interface. It also provides
structural support for the digital board and the battery contacts. It contains
attachments for the sensor connector, rotary encoder, and serial port. It also
provides the grounding system for the case shield with EMC capacitors to shunt
high-frequency currents.
VCC
UPS
-V
-PROBE
D
I
G
I
T
A
L
B
O
A
R
D
>
INTDET-
AVG DRV
VREF
LEDDRV
LOBAT
AMUX
INTF
MUX 0-3 , MUX 3-
ACA - ACC
VERN
RED
IR
RLT
IRLT
DARK
DLT
PETE
DISABLE
+VSW
REXPULSE
REXCHA
REXCHB
REXPB
OPERATE / TEST
TXD
RXD
GROUND*
A
N
A
L
O
G
5
B
O
A
R
D
<
>
<
GROUND
<
DETECTOR
DET RETURN*
IR CATHODS
RED CATHODE
ANODES*
PROBE ID
ID RETURN
VBATT
BATMON
BATTERY RETURN*
GROUND*
GROUND*
REXPULSE
REXCHA
REXCHB
REXPB
SERIAL PORT
Sensor
Battery
assembly
Rotary
encoder
*Essential grounds
1-6
Figure 1-5. Analog board and digital board system
Note: The rotary encoder is installed on the 3775 analog board only; in all other
respects the 3770 and 3775 analog boards and their components are identical.
Specifications
Electromagnetic effects
1/Overview
Unless otherwise indicated, all specifications are nominal and are subject to
change without notice. Unless otherwise indicated, the specifications below apply
to both oximeters.
The 3770 or the 3775 when used with a LR6 (AA) battery pack, a NiCd battery
pack, or a NiCd battery pack in a battery charger monitoring station are referred
to as the “system” for EMC purposes.
• Indications that the system is experiencing electromagnetic interference
include:
• Variations in the display (pleth bar does not correlate to physiological signals).
• Sudden increases or decreases in the signal strength indicator that do not
correlate to physiological condition of the patient.
• PROBE? messages that are not resolved by the instructions found in the
3770/3775 Pulse Oximeter User’s
•
T
he display of “rolling dots” when a valid physiological signal is present.
Manua.
This interference may be intermittent and careful correlation between the effect
and its possible source is important. The system will not display any of these
indications if it is used within its intended electromagnetic environment.
Environment
Suitable for use in the environment described in IEC/EN 60601-1-2 (1993).
EMC performance
The system complies with the requirements of IEC/EN 60601-1-2 (Electromagnetic
compatibility - Requirements and tests). The following basic EMC standards were
applied to verify conformance.
Emissions: IEC/EN 55011 Group I, Class B (1997)
Immunity: IEC/EN 61000-4-2 (1995), 8 kV air, 3kV contact
IEC/EN 61000-4-3 (1995), 3 V/m
IEC/EN 61000-4-4 (1995), 2 kV power, 1kV I/O
IEC/EN 61000-4-5(1995), 2 kV line to earth, 1 kV line to line
International Electrotechnical Commission (IEC) classifications
The oximeter complies with the requirements of IEC/EN 60601-1 (1988) Part 1:
General requirements for safety of medical electrical equipment:
Degree of protection against electric shock: Type BF applied part
IPX3
Type of protection against electric shock: Internally powered equipment/Class II
Mode of operation: Continuous
Degree of protection against ingress of liquids: Sprayproof (IEC/EN 60529)
1-7
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