Nellcor N-180 User manual

NELLCOR®
© © SERVİCE MANUAL
NELLCOR® N-180/N-180E
Pulse Oximeter
-To contact Nellcor's representative: In the United States, call 1-800-NELLCOR 一
ro or 510 887-5858; outside of the United States, call Nellcor's local representative.
Caution: Federal law (U.S.) restricts this device to sale by or on the order of a physician.
© 1993 Nellcor Incorporated 028018A-0993

Corporate Headquarters
‘European Office
Nellcor Incorporated Nellcor BV
25495 Whitesell Street Hambakenwetering 1
Hayward, California 94545 5231 DD ’s-Hertogenbosch
U.S.A. The Netherlands
Tel. [phone]
European Regional Offices European Local Offices
Northwest Europe Nellcor (UK) Limited
Nellcor Europe BV University of Warwick
Hambakenwetering 1 Science Park
5231 DD ’s-Hertogenbosch Coventry CV4 7EZ
The Netherlands United Kingdom —
Tel. [phone] Tel. [phone]
Middle and Central Europe Nelicor (Belgium) NV/SA
Nellcor GmbH Interleuvenlaan 62/8
Black-&-Decker-Strasse 28 B-3001 Leuven
65510 Idstein Belgium
Germany Tel. [phone]
Tel. [phone]
Asia/Pacific Headguarters
Southern Europe
Nellcor Sarl Nellcor Limited
8, rue du Petit Robinson Suite 1204C
78353 Jouy-en-Josas Cedex Admiralty Centre, Tower 1
France 18 Harcourt Road
Tel. [phone] Hong Kong
Tel. [phone]
Tel. [phone]
The following are trademarks of Nellcor Incorporated: NELLCOR, which is registered in the United
‘States and other countries; DURASENSOR, and OXIBAND, which are registered in the United States;
and OXISENSOR, DURAFORM, and the Nelicor knob, which are commercial trademarks.
Covered by one or more of the following patents and corresponding foreign patents: U.S, Patent
Numbers 4,621,643; 4,653,498; 4,700,708; 4,770,179; 4,869,254,

CONTENTS
Figures
Tables
Symbols vii
Graphics .. G1
introduction GA
Graphies Listed. Gl
Introduction ........... 1-1
Manual Overview .... 1-1
Warnings, Cautions, And Notes .. 1-1
N-180/N-180E Pulse Oximeter Monitors Described 1-1
Related Documents .... 1-2
Conventions Used in TI 1-2
Returning the Monitor........... 1-3
Principles Of Pulse Oximetry 2-1
Introduction................. 2-1
Automatic Calibration . 2-1
Functional Versus Fractional Saturation .. 2-1
Measured Versus Calculated Saturation .. 2-2
Functional Block And Circuit Analysis 31
Infroductioh ee 8-1
Functional Block Analysis. 8-1
Circuit Analysis ....... 34
Routine Maintenance... 41
Introduction ............. 4-1
Nellcor Recommendation . 41
Troubleshooting .. 5-1
introduction...... 5-1
How to Use This Section 5-1
Who Should Perform Repairs.. 5-1
Replacement Level Supported 5-1
Obtaining Replacement Parts . 5-1
Troubleshooting Guide ............ 5-1
Disassembly and Assembly Guide 6-1
Introduction... 6-1
Tools Require 6-1
-Preliminary Procedures and Precautions . 6-1
Post Asssembly Testing Requirements. 6-1
Top Level View of Monitor Assemblies. 6-1
Wiring Connections ... 6-2
Procedures... 6-3
Gaining Acces ponen: 6-3
Performance And Safety Tests... 7-1
Introduction... 7-1
Required Test Equipment... 7-1
Building the Test Adapters and Fixtures . 7-1
Testing Performance . 7-2
Safety Tests .... 7-11
Specifications .. 8-1
Performance .... 8-1
Environmenta! Requirements .. 82
Electrical Characteristics .. 82
Physical Characteristics 8-3
Spare Parts........ 9-1
Introduction 9-1
Spare Parts Listings .. 91

Contenis
FIGURES
FO10-4: N-180 LED PCB Schematic Diagram
Schematic Diagrams...
Introduction .......
Schematic List ......
Communications Formats.
Introduction... . A
Conversation Format A-1
Computer Format A1
FOG-1: Monitor Functional Block Diagram ... G2
-1: Oxyhemogiobin Dissociation Curve . 22
8-1: Oximetry Module Block Diagram... 32
3-2: Oximetry Module LED Driver Circuit 35
3-3: Oximetry Module Input Source Selection Circuits. 37
3-4: Oximetry Module Input Amplifier, Synchronous Detector,
and Filter and Amplifiers 3-9
3-5: Oximetry Module Analog to Digital Conversion Circuits 3-13
3-6: Oximetry Module Support Circuits... ee 8-14
5-1: Display Troubleshooting Decision Tree (1 of 4). 54
5-1: Display Troubleshooting Decision Tree (2 of 4). 5-6
5-1. Display Troubleshooting Decision Tree (3 of 4). 5-8
5-1: Display Troubleshooting Decision Tree (4 of 4). 5-10
5-2: Front Panel Decision Tree (1 of 2) ... 5-12
5-2: Front Panel Decision Tree (2 of 2) 5-14
6-1: Exploded View of Monitor... 62
6-2: Monitor Cabling Diagram ... 6-3
6-3: Battery and Associated Components 65
. 6-4: Removing the Top Shield............... 6-6
6-5: Transformer and AC Filter Details 6-7
6-6: Middle Shield Components... 6-10
6-7 Bottom Shield Components .. 6-11
6-8: AC Power Inlet and Control Assembly . 6-12
6-9: Fuse Holder ve. 6-13
6-10: Front Panel Assembly 6-14
6-11: Sensor Connector Assembly Components … 6-16
6-12: Bail and Feet ........... . 6-17
7-1: Test Adapier One 7-2
7-2: RCAL Hi Test Fixture... 7-2
FO10-1: - MINI SOOM Schematic Diagram (1 of 7) 10-3
FO10-1: MINI SOOM Schematic Diagram (2 of 7) 10-5
FO10-1: MINI SOOM Schematic Diagram (3 of 7) 10-7
FO10-1: MINI SOOM Schematic Diagram (4 of 7) 10-9
FO10-1: MIN! SOOM Schematic Diagram (5 of 7) ... . 10-11
FO10-1: MIN! SOOM Schematic Diagram (6 of 7) ... . 10-13
FO10-1: MINI SOOM Schematic Diagram (7 of 7) . 10-15
FO10-2: CPU PCB Schematic Diagram (1 of 4).... 10-17
FO10-2: CPU PCB Schematic Diagram (2 of 4) . 10-19
FO10-2: CPU PCB Schematic Diagram (3 of 4) . 10-21
FO10-2: CPU PCB Schematic Diagram (4 of 4).... 10-23
FO10-3: N-185 LED Drive PCB Schematic Diagram

TABLES
5-11:
5-12:
5-13:
5-14:
5-15:
5-16:
5-17:
5-18:
5-19:
7-1:
9-1:
9-2:
AT:
Contents
Status Messages by Category... ner 5-2
Erratic or Missing Values .. . 55
Fixed Error Values ......... 5-5
Missing Display Segmenis 5-5
Intermittenily Lighted... 5-7
Partially Lighted .. 5-7
Not Lighted... 5-7
AC Operation 5-9
Battery Operation ..... 5-9
Normal Audio When Power is Applied... 5-11
Missing One or More Displays or Indicators 5-11
Front Panel Control Knob ........................ 5-13
Cannot Turn On Monitor {ac Operation) .. 5-13
Cannot Tum On Monitor (Battery Operatio: 5-15
Cannot Tum Off Monitor ... 5-15
Push Buttons..................... 5-15
DIP Selector Switch Troubleshooting Chart. 5-16
Power Switch Troubleshooting Chart............ 5-16
RS-232 Communications Port Troubleshooting Chart.. 5-16
Required Test Equipment ........................ 7-1
Spare Parts Listed in Part Number Order 9-2
Spare Parts by Description and ltem Order . 9-3
Serial Data Output A-2

_ SYMBOLS
0/0
" Sp02%
Caution: refer to manual
Type BF equipment; patient electrically isolated
Fuse replacement symbol
(110-120 VAC)
Fuse replacement symbol
(220-240 V~)
DANGER: High voltage.
Equipotential ground
Audible Alarm Off
STDBY/ON switch
Percentage OXYGEN SATURATION
vii

Symbols
The following symbols apply only to the N-180E model.
© min
©
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PULSE RATE, measured in beats per minute (bpm)
PULSE SEARCH indicator
BATT IN USE
LOW BATT indicator
HIGH SAT
LOW SAT
HIGH RATE
LOW RATE

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SECTION 1: INTRODUCTION
Manual Overview
Warnings, Cautions, and Notes
N-180 Puise Oximeter Monitor Description
Related Documents
Conventions Used in this Manual
Returning the Monitor
MANUAL OVERVIEW
This manual contains information for servicing the Nellcor N-180 pulse
oximeter, and is only for individuals who have a technical background in
analog and digital electronics. This product must beserviced by qualified
personnel. Before servicing the N-180, read the operator's manual carefully
for a thorough understanding of how this device operates.
WARNINGS, CAUTIONS, AND NOTES
Warning
Caution
Note
This manual uses three terms that are important for proper operation of the
monitor: Warning, Caution, and Note.
A warning precedes an action that may result in injury or death to the patient
or user. Warnings are boxed and highlighted in boldface type.
Warning: This is an example of a warning. This is an
example of a warning. This is an example of a
warning.
A caution precedes an action that may result in damage to, or malfunction of,
the monitor. Cautions are highlighted in boldface type.
Caution: This is an example of a caution. This is an example of a
caution, This is an example of a caution
A note gives information that requires special attention. Here is an example:
Note: This is an example of a note. This is an example of a note. This
is an example of a note. This is an example of a note.
N-180/N-180E PULSE OXIMETER MONITORS DESCRIBED
The N-180/N-180E Pulse Oximeter Monitors (to simplify writing and reading
this manual, the term monitor is substituted from this point on) continuously
and noninvasively measures functional oxygen saturation of arterial hemo-
globin (SpOz), and pulse rate. Measurements are updated at each pulse beat.
1-1

N-180 Pulse Oximeter Service Manual
These monitors are manufactured in a domestic and an international
configuration. The domestic version uses standard English markings; the
international version uses symbolic markings. Except where there is a clear
need to distinguish between monitor versions the single term monitor applies
to either version. ・
The domestic version (N-180) operates on 110-120 VAC and the international
version (N-180E) operates on 220-240 VAC. There are also differences in the
way controls are marked. Because of the different operating voltages, the
following electrical components differ.
* Transformer
* AC inlet
* Fuse
The parts listings in Section 9, Parts List, distinguish between the models
where such distinctions are needed.
The physical and operational characteristics of these monitors are completely
described in the respective operators manuals. These manuals and other
publications that apply to operating and servicing the monitor are described
in the following paragraph.
RELATED DOCUMENTS
To perform test and troubleshooting procedures and to understand the
principles of operation and circuit analysis sections of this manual, you must
know how to operate the monitor. Refer to Operators Manual Nellcor N-180
Pulse Oximeter or to Operators Manual Nellcor N-180E Pulse Oximeter, as
applicable.
To understand the various Nellcor sensors that work with the monitor, refer
to the Nellcor poster Pulse Oximetry or to the information supplied with your
individual sensors.
CONVENTIONS USED IN THIS MANUAL
The following conventions are used in this manual:
12

Section 1: Introduction
* In text, active low logic signals are designated by an asterisk after the
signal name (for example SIGNAL*). On logic diagrams a virgule ()
before or after the signal name designates logic low active. In addition,
an over score also designates logic low on some schematic device
symbols,
* Signal names are printed in all capital letters.
« Fold out illustration numbers are preceded by the letters FO.
. The front panel switch that controls operating power to the monitor
bears symbolic marks that are difficult to set in type. Therefore, the
term ON/STDBY is substituted for the symbolic marking.
RETURNING THE MONITOR
If you must return the monitor to Nelicor, call Nellcor’s Technical Services
department for shipping instructions. To facilitate repair or replacement
processing Nellcor will give you a return goods authorization (RGA) number.
To repackage the CO2 indicator disconnect the sensor and the power cable.
Carefully pack the monitor in the original shipping carton. If the original
carton is unavailable, use a suitable carton with an appropriate amount of
packing material. Mark the shipping carton and any shipping forms with the
RGA number.
13

SECTION 2: PRINCIPLES OF PULSE OXIMETRY
Introduction
Automatic Calibration
Functional Versus Fractional Saturation
Measured Versus Calculated Saturation
INTRODUCTION
Pulse oximetry is based on two principles: that oxyhemoglobin and deoxyhe-
moglobin differ in their absorption of red and infrared light, and that the vol-
ume of arterial blood in tissue (and hence, light absorption by that blood)
changes during the pulsatile cycle. A pulse oximeter measures the oxygen
saturation of arterial hemoglobin (SpO2) by passing red and infrared light
into an arteriolar bed and determining light absorption. Two low-power light-
emitting diodes (LEDs) in the oximetry sensor serve as light sources (red,
nominally 660 nm; infrared, nominally 920 nm); a photodiode serves as the
photo detector.
Because oxyhemoglobin and deoxyhemoglobin differ in spectral absorption,
the relative absorption of red and infrared light by blood reflects hemoglobin
oxygen saturation. To identify arterial hemoglobin oxygen saturation, the
monitor relies on the pulsatile nature of arterial flow. At systole—as a new
pulse of arterial blood enters the vascular bed—blood volume, and hence light
absorption, increases. During diastole, blood volume and light absorption
‘reach their lowest point. To measure SpO2, the monitor uses the difference
between minimum and maximum absorption of red and infrared light.
Accordingly, the effects of nonpulsatile absorbers (that is, tissue, bone, venous
blood) are eliminated. Red absorption and infrared absorption that are at-
. tributable to the pulsatile arterial blood are thus made distinct. .
AUTOMATIC CALIBRATION
Because light absorption by hemoglobin depends upon wavelength and the
mean wavelength of LEDs vary, an oximeter must store the mean wavelength
of the sensor red LED to accurately measure SpO2. (The mean wavelength of
the infrared LED is less crucial because the hemoglobin absorption curves are
relatively flat in the portion of the infrared spectrum used.) Patented mech-
anisms automatically calibrate the monitor for the sensor red wavelength
when the monitor is turned on. Calibration occurs periodically thereafter and
each time a new sensor is connected. During manufacturing, the mean
wavelength of the red LED is encoded in a resistor in the sensor. The monitor
software reads this resistor and selects appropriate calibration coefficients for
that sensor.
FUNCTIONAL VERSUS FRACTIONAL SATURATION
This monitor measures functional SpO2—oxygenated hemoglobin expressed
as a percentage of the hemoglobin that is capable of transporting oxygen.
Significant amounts of dysfunctional hemoglobin, such as carboxyhemoglobin
or methemoglobin are not detected. İn contrast, hemoximeters such as the II,
282 report fractional saturation—oxygenated hemoglobin expressed as a per-
centage of all measured hemoglobin, including measured dysfunctional
hemoglobins. To compare functional SpO2 measurements to those from an in
21

N-180 Pulse Oximeter Service Manual
strument that measures fractional saturation, you must convert fractional
measurements using the following equation:
functional SpO2 = fractional saturation
100
100- (% carboxyhemoglobin + % methemoglobin) х
MEASURED VERSUS CALCULATED SATURATION
2-2
When saturation is calculated from a blood gas measurement of the partial
pressure of arterial oxygen (PaO2), the calculated value may differ from mea-
sured SpO2. This is because the calculated saturation may not have been cor-
rected for the effects of variables that shift the relationship between PaO2
and saturation (figure 2-1). The variables are: pH, temperature, the partial
pressure of arterial carbon dioxide (PaCO2), and the concentrations of
2,3-DPG and fetal hemoglobin.
100
50
(%)
SpO2
PaO2 (mmHg)
Figure 2-1: | Oxyhemogiobin Dissociation Curve

SECTION 3: FUNCTIONAL BLOCK AND CIRCUIT ANALYSIS
Introduction
Functional Block Analysis
Circuit Analysis
INTRODUCTION
This section explains how monitor circuits operate and contains two parts.
Functional block diagram analysis
+ Circuit analysis
FUNCTIONAL BLOCK ANALYSIS
Monitor functional elements (figure FOG-1) include:
* Standard original equipment manufacturer (OEM) oximetry module
(SOOM), model MP-203 oximetry module. For ease of reference this
module is hereafter referred to as the oximetry module. In actual fact,
the oximetry module is a printed circuit board (PCB).
* CPU PCB
e LED Drive PCB
* LED PCB
* Front panel controls
* AC power inlet
® Battery
Oximetry Module
The oximetry module (figure 3-1) drives the oxygen transducer and conditions
the signal derived from the patient (via the sensor connector).
31

N-180 Pulse Oximeter Service Manual
The functional elements of the oximetry module are:
* LED driver
* Input amplifier and synchronous detector
+ Input source selection
* Demodulator filters and amplifiers
+ © Analog to digital converter
* Support circuits
JP4
ET- Extemal
Power Option Support Data and Control LED Pre-amp
Selector Circuits + Driver — Connector
JP3
JP5
Host Comm Lines
Input Amplifier
Power A:D and
Host Power and Coriverter Synchronous
Communications Detector
JPt
Red ADC Saturation Signal
Red
Filters Input Source Sensor
Configuration IR Selection
dumpers IR_ADC Connector
Figure 3-1: Oximetry Module Block Diagram
The patient signal (SAT for saturation), is conditioned and used to derive sat-
uration percentage and pulse rate values. This same patient information is
serial coupled to the CPU PCB and processed for display and for output
through the serial communication port.
Section 2, Principles of Pulse Oximetry, explains how Nellcor sensors operate.
An oxygen saturation signal is obtained from a Nellcor oxygen transducer at
‘the selected patient measurement site such as a finger, nose or toe. Sensor
LEDs generate alternate infrared and red light pulses at this site. A photodi-
ode in the transducer responds to the modulated light energy transmitted
through the measurement site. The photodiode SAT signal is coupled into the
oximetry module via the monitor front-panel sensor connector.
LED Driver
The LED drive circuits control the current to, and the timing of, the sensor
LEDs. The current is controlled to maintain an optimal signal to noise ratio.
Input Amplifier and Synchronous Detector
The SAT signal is conditioned by the input amplifier and the synchronous
detector to provide signal gain and reduce or eliminate the effects of ambient
interference (such things as ambient light and spurious electrical noise). The
final analog conditioning of the SAT signal is accomplished by circuits in the
filter block.
3-2

CPU PCB
Section 3: Functional Block and Circuit Analysis
Input Source Selection
There are two possible inputs to the oximetry module. These inputs are
controlled via the LEMO signal. Only one input is used in the model N-180,
the differential input at JP1. If more than one input were used, the input
source selection logic detects which input connector is active.
Connector JP1 goes to an internal preamplifier. The signal at connector JP3
requires an external preamplifier.
Demodulator Filters and Amplifiers
The oximetry module includes two separate active filter channels, IR and red.
These low-pass filter and amplifier circuits and associated gate circuits
recover the patient’s pulse waveform from the SAT signal. The next step is to
digitize these pulse waveforms in the analog to digital converter circuit block.
Analog to Digital Conversion
The analog to digital conversion block digitizes the demodulated IR and red
signals. Sensor calibration information is also digitized for use in the
saturation calculation algorithms.
Support Circuits
Support circuits include the following:
* Processor Circuits
* Power
Oximetry module operations are controlled by an 80C552 micro controller
supported by 512K electrically programmable read only memory (EPROM)
and 256K random access memory (RAM). Module power is supplied by the
CPU PCB via connector JP5.
- Besides acting as a central controller and processing data from the oximetry
‘module for display on the front panel LEDs, the multipurpose CPU PCB
includes:
a speaker driver
an LED current check function
a battery charger
a battery condition monitor
a power control
a set of optical isolators for the RS-232 lines
an RS-232 connector
Front Panel LED Displays
Front panel displays consist of LEDs that show SpO2 (saturation), pulse rate
and relative pulse strength. The relative pulse strength indicator is a bar
graph arrangement that does not have a legend. Status indicators are:
33

N-180 Pulse Oximeter Service Manual
+ Battery in use
ㆍ Low batt
+ Pulse search
* Neonatal
Alarm status is conveyed by four red LEDs mounted bebind the front panel
membrane next to the five push-button switches. These respective LEDs light
when the corresponding alarm condition occurs:
High saturation
Low saturation
High rate
Low rate
A fifth LED flashes once per second to show the audio alarm function is
temporarily silenced or lights continuously if the alarm is disabled.
The front panel assembly includes the sensor input connector, LED Drive
PCB, LED PCB, and the front panel controls (push buttons, control knob, and
ON/STDBY switch). (This assembly is not available as a spare part but some
elements,
such as the PCBS are included on the spares list in section 9.)
AC Power Input and Control
Battery
CIRCUIT ANALYSIS
Oximetry Module
The AC power input and control includes the AC input receptacle, AC Power
switch, two fuses, and a filter.
The monitor takes DC power from an internal 12 volt sealed lead-acid
battery. The battery is self-contained and connects directly to the CPU PCB
at CN4. The battery charging circuit is on the CPU PCB.
This portion of section three describes major functional circuit blocks in
detail. An understanding of monitor operation helps you locate and repair
malfunctions. The descriptions are organized in top-down order. Each monitor
PCB has an associated circuit analysis paragraph in this section.
The oximetry module is a self-contained assembly that provides oxygen
transducer power, conditions the resulting SAT signal, and calculates patient
oxygen saturation and pulse rate. The saturation percentage, pulse rate, and
other pertinent information are transmitted to the monitor CPU PCB for
processing.
The functional elements of the oximeter module are as follows:

Section 3: Functional Block and Circuit Analysis
LED. Drive
Input source selection
Input amplifier and synchronous detector
Demodulator filters and amplifiers
Control signals
Analog to digital converter
Support circuits
“eso
co.“
LED Drive Circuit
The SAT signal development scheme requires lighting the measurement site
using specific light wavelengths. Nellcor sensors have two LED sources,
infrared (IR) and red. These LED sources are an integral part of each Nellcor
oxygen transducer. The LEDs are alternately pulsed on and off by the
oximetry module microprocessor.
The LED drive bias voltages are developed by dual DAC 01 (figure 3-2).
Initially, both DACs in U1 are directed via the DACBUS to develop
approximately 0.5 VDC on respective outputs (pins 4 and 18) coincident with
the period each LED is selected. The microprocessor alternately closes FET
switches U4A and U4B via control lines IRLED* (U4 pin 16) and REDLED*
(U4A, pin 1). The DAC outputs are gated by these signals and output on pin 2
and pin 15 of U4. '
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Figure 3-2: Oximetry Module LED Driver Circuit