Novametrix Medical Systems 509 User manual

Novametrix Medical Systems Inc.
P.O. Box 690
5 Technology Drive
Wallingford, Connecticut, U.S.A. 06492.
Model 509
Service Manual
Jan 26, 2000
Part Number 6900-90-00

Rev. 00 Model 509 Service Manua iii
Revision History 26-Jan-00 Preliminary
Guarantee Equipment manufactured or distributed by Novametrix Medical Systems Inc., is fully guaranteed,
covering materials and workmanship, for a period of one year from the date of shipment, except for
certain disposable products and products with stated guarantees other than one year. Novametrix
reserves the right to perform guarantee service(s) at its factory, at an authorized repair station, or at
the customer’s installation.
Novametrix’ obligations under this guarantee are limited to repairs, or at Novametrix’ option,
replacement of any defective parts of our equipment, except fuses, batteries, and calibration gasses,
without charge, if said defects occur during normal service.
Claims for damages during shipment must be filed promptly with the transportation company. All
correspondence concerning the equipment must specify both the model name and number, and the
serial number as it appears on the equipment.
Improper use, mishandling, tampering with, or operation of the equipment without following specific
operating instructions will void this guarantee and release Novametrix from any further guarantee
obligations.
Caution: Federal (U.S.A.) law restricts this device to sale, distribution, or use by or on the order of a
licensed medical practitioner.
Copyright 2000, Novametrix Medical Systems Inc. This document contains information which is
proprietary and the property of Novametrix Medical Systems Inc., and may not be reproduced, stored
in a retrieval system, translated, transcribed, or transmitted, in any form, or by any means, without
prior explicit written permission from Novametrix Medical Systems Inc.
Service Department
For factory repair service, call toll free
1-800-243-3444
In Connecticut, call Collect [phone]
Facsimile [phone]
World Wide Web: http://www.novametrix.com
Internet: [e-mail]

iv Model 509 Service Manual Rev. 00
Service Policy Novametrix Medical Systems Inc. provides 24-hour a day access to technical support through its Technical
Support Department in Wallingford, Connecticut, and company Service Representatives located throughout
the United States. (Outside the U.S., primary technical support is handled through our qualified international
sales and service distributors.
Novametrix will provide Warranty Service support within 48 hours of receiving a request for assistance
Contact the Technical Support Department by telephone toll free at 800-243-3444, or 203-265-7701; by
facsimile at 203-284-0753; or, by e-mail at [e-mail]. After hours telephone support
requests (before 8:00 AM and after 5:00 PM Eastern Time) will be responded to promptly by the Technical
Support on-call staff. After hours facsimile and e-mail requests will be answered the next business day. It is
suggested that any person calling in for technical support have the equipment available for product
identification and preliminary troubleshooting.
Novametrix reserves the right to repair or replace any product found to be defective during the warranty
period. Repair may be provided in the form of replacement exchange parts or accessories, on-site technical
repair assistance or complete system exchanges. Repairs provided due to product abuse or misuse will be
considered “non-warranty” and invoiced at the prevailing service rate. Replaced or exchanged materials are
expected to be returned to Novametrix within 10 days in order to avoid (additional) charges. Return materials
should be cleaned as necessary and sent directly to Novametrix using the return paperwork and shipping
label(s) provided (Transferring return materials to a local sales or dealer representatives does not absolve
you of your return responsibility.).
Novametrix manufactures equipment that is generally field serviceable. When repair parts are provided, the
recipient can callTechnical Support for parts replacement assistance and repair assurance. In the event a
replacement part requires increased technical capability, Technical Support may request Biomedical
assistance, provide on-site technical support or complete replacement equipment. If the customer requires
the return of their original product, the exchange material will be considered “loaner material” and exchanged
again after the customer equipment is repaired.
Novametrix promotes customer participation in warranty repairs, should they become necessary. A longer
useful product life, and quicker, more cost-effective maintenance and repair cycles—both during and after
the warranty period, are benefits of a smooth transition into self-maintenance. The Technical Support
Department can provide technical product support at a level appropriate to your protocol and budget
requirements.
Please contact Technical Support for information on these additional programs and services:
• Focus Series Technical Training Seminars
• Test Equipment and Test Kits
• Service Contract / Parts Insurance Plans
• On-Site Technical Support
• “Demand Services” including:
Flat rate parts exchange
Flat rate return for repair
Time and material,
Full warranty, discounted replacement sensors.
Declaration of
Conformity
with European
Union Directive
The authorized representative for Novametrix Equipment is:
D.R.M. Green
European Compliance Services Limited,
Oakdene House,
Oak Road,
Watchfield
Swindon, Wilts SN 6 8TD
United Kingdo

Rev. 00 Model 509 Service Manua v
1Table of Contens
Patient Safety ....................................................................................................................1
Indications and Usage ....................................................................................................2
Front and Rear Panel Illustrations .....................................................................................5
Front Panel Illustration ...................................................................................................5
Rear Panel Illustration ....................................................................................................6
Electronic Theory of Operation ..........................................................................................7
2543 Main Board ............................................................................................................7
2581 Power Board ........................................................................................................13
2542 Display Board ......................................................................................................14
Functional Tests ..............................................................................................................15
Equipment Required .....................................................................................................15
Procedure .....................................................................................................................15
Accuracy Tests ................................................................................................................17
Equipment Required .....................................................................................................17
Procedure .....................................................................................................................17
Electronic Tests ...............................................................................................................19
Equipment Required .....................................................................................................19
Procedure .....................................................................................................................20
Safety Testing ..............................................................................................................22
Maintenance ....................................................................................................................23
Maintenance Schedules ...............................................................................................23
Cleaning and Sterilization .............................................................................................23
Assembly Exchanges ...................................................................................................25
Battery Replacement ....................................................................................................26
Software Update Instructions .......................................................................................27
Troubleshooting ...............................................................................................................29
Status Messages ..........................................................................................................29
Specifications ...................................................................................................................31
SpO2 (Oxygen Saturation) ...........................................................................................31
Pulse Rate ....................................................................................................................31
General Specifications .................................................................................................31
Parts Lists ........................................................................................................................33
6900-00 Pulse Oximetry Interface ................................................................................33
6900-01 Main Assy Model 509 ....................................................................................33

vi Model 509 Service Manual Rev. 00
2542-01 Display Board Assy, Front ............................................................................. 33
2543-01 Main Board Assy, ...........................................................................................34
2581-01 Power Board Assy, ........................................................................................36
Schematics and Assembly Drawings .............................................................................. 37

Rev. 00 Model 509 Service Manual 1
2Patient Safety
Pulse oximetry is a non-invasive method of monitoring the oxygen saturation of arterial
blood. Pulse oximeters display oxygen saturation of functional hemoglobin and
therefore the accuracy may be interfered with by carboxyhemoglobin or other
dysfunctional hemoglobins present in significant concentrations. Oxygen saturation
monitoring is intended to be used in a variety of clinical situations, including, but not
limited to respiratory therapy, anesthesia, intensive care, and emergency.
The Model 509 Pulse Oximetry Interface Module SpO2input is electrically isolated.
Patient leakage current flowing from the instrument to ground is limited to less than 50
µA at 120 VAC, 60 Hz. Patient isolation is tested at 2500 VAC rms at 60 Hz.
For maximum patient and operator safety, the following are recommended:
•Failure of Operation: If the module fails to respond as described, do not use it
until the situation has been corrected by qualified personnel.
• Keep the Model 509 and its accessories clean.
• Do not operate the Model 509 when it is wet due to spills or condensation.
• Do not operate the Model 509 if it appears to have been dropped or damaged.
• Connect the Model 509 only to Novametrix approved power supply.
• Connect the external supply only to a grounded hospital grade outlet. It should
be connected to the same electrical circuit as the equipment it is used with.
Outlets on the same electrical circuit can be identified by the hospital’s
engineering department.
• Care should be exercised to assure continued peripheral perfusion distal to the
SpO2sensor site after application.
•Do
NOT attach an SpO2sensor distal to a blood pressure cuff. Valid data
CANNOT be processed when the cuff is inflated. Attach the sensor to the limb
opposite to the site used for the blood pressure cuff.
• Do NOT wrap the sensor tape around the limb so tightly that circulation is
restricted. Inspect the site often for adequate circulation - at least once every four
hours. When applying sensors take not of the patient’s physiological condition.
For example, burn patients may exhibit more sensitivity to heat and pressure and
therefore additional consideration such as more frequent site checks may be
appropriate.
• Connect the Model 509 external interface cable (Cat. No. 6905-00) to VueLink
modules only.

2 Patient Safety Indications and Usage
2Model 509 Service Manual Rev. 00
2.1 Indications and Usage
The Model 509 Pulse Oximetry Interface Module is intended to be used in conjunction
with Hewlett Packard VueLink Gas Analyzer modules (Cat. # M1032A with option A03)
and supported patient monitoring systems. The Model 509 is intended to be used for
monitoring oxygen saturation and pulse rate in all critical monitoring environments in all
patient areas including adult, pediatric and neonatal.
•Explosion Hazard: Do NOT use the Model 509 in the presence of flammable
anesthetics. Use of this instrument in such an environment may present an
explosion hazard.
•Electrical Shock Hazard: Always turn the Model 509 off and disconnect it from
any equipment before cleaning it. Do NOT use a damaged sensor or one with
exposed electrical contacts. Refer servicing to qualified service personnel.
• Do not operate the Model 509 when it is wet due to spills or condensation.
• Do not operate the Model 509 if it appears to have been dropped or damaged.
•Failure of Operation: If the monitor fails to respond as described, do not use it
until the situation has been corrected by qualified personnel.
•Patient Safety: Care should be exercised to assure continued peripheral
perfusion distal to the SpO2sensor site after application.
•Data Validity: As with all pulse oximeters, inaccurate SpO2and Pulse Rate
values may be caused by
• Incorrect application or use of a sensor
• Significant levels of dysfunctional hemoglobin; carboxyhemoglobin or
methemoglobin
• Significant levels of indocyanine green, methylene blue, or other intravascular dyes
• Exposure to excessive illumination such as surgical lamps—especially ones with a
xenon light source, or direct sunlight
• Excessive patient movement
• Venous pulsations
• Electrosurgical interference
•Data Validity: Do NOT attach a sensor distal to a blood pressure cuff. Valid data
CANNOT be processed when the cuff is inflated. Attach the sensor to the limb
opposite to the site used for the blood pressure cuff.
•Do Not apply Y-Sensor tapes or wraps so tightly that circulation is restricted.
Inspect site often for adequate circulation - at least once every four hours. When
applying sensors take note of patient’s physiological condition. For example,
burn patients may exhibit more sensitivity to heat and pressure and therefore
additional consideration such as more frequent site checks may be appropriate.
• Electric shock hazard. Do NOT remove covers or panels. Refer servicing to
qualified service personnel.
NOTE: Components of this product and its associated accessories which may have
patient contact are free of latex.
WARNING: Indicates a potentially harmful condition that can lead to personal injury.
!

Indications and Usage Patient Safety 2
Rev. 00 Model 509 Service Manual 3
• Do not operate Model 509 when it is wet due to spills or condensation.
• Do not operate Model 509 if it appears to have been dropped or damaged.
• Never sterilize or immerse the monitor in liquids.
• Do not sterilize or immerse sensors except as directed in this manual.
• No tension should be applied to any sensor cable.
• Do not store the monitor or sensors at temperatures less than 14 °F (-10 °C) or
greater than 131 °F (55 °C).
• Do not operate the monitor or sensors at temperatures less than 50 °F (10 °C) or
greater than 104 °F (40 °C).
• Caution: Federal (U.S.A.) law restricts this device to sale, distribution, or use by
or on the order of a licensed medical practitioner.
• Overstretching the pulse oximeter finger sensor can damage the sensor and
potentially affect pulse oximeter readings. Do not stretch the finger sensor open
beyond the limit for which it was designed. Overstretching can be prevented:
avoid opening the sensor by any means other than squeezing the grips; DO NOT
force the sensor onto large objects such as a bed rail.
• Electric shock hazard. Do NOT remove covers or panels. Refer servicing to
qualified service personnel.
• For continued protection against fire hazard, replace fuse only with those of the
same type and rating.
CAUTION: Indicates a condition that may lead to equipment damage or malfunction.

2 Patient Safety Indications and Usage
4Model 509 Service Manual Rev. 00
[This page intentionally blank.]

Rev. 00 Model 509 Service Manual 5
3Front and Rear Panel Illustrations
3.1 Front Panel Illustration
AUDIO key-Press for two
minute silence. Press and
hold to permanently mute
audible alert. Press again to
cancel two minute silence or
audible alert mute.
SpO2High Limit display-Upper limit value
displayed during normal monitoring.
Displays “ ” , “VOL”, “BEEP” or “AUTO”
depending upon the function selected by
the key.
SET key-Use to select
between alert limits, pulse
beep volume and alert
volume.
SpO2Low Limit display-Lower limit value
during normal monitoring. Displa ys “”,
volume setting value, pulse beep value, or
“LMTS” depending upon the function
selected by the key.
ADJUSTMENT keys-Use to
adjust selected option’s
value.
Power indicator LED-Lights green when
the Model 509 is powered.
SpO2sensor input connector-
For connection of Novametrix
SuperBright series sensors.
Alert Icon- Flashes red when an alert
condition is detected. This icon is visible
only when indicating an alert.
AUDIO key
SET key
SpO2High Alert Limit displa
SpO2Low Alert Limit display
Adjustment keys
Power indicator LED
SpO2sensor input connector
Alert Icon (visible only during alert)

3 Front and Rear Panel Illustrations Rear Panel Illustration
6Model 509 Service Manual Rev. 00
3.2 Rear Panel Illustration
Power switch- “|” - ON turns
module on, “O” - OFF turns
module off.
Power jack-Connect only to Novametrix
power supply catalog number 9598-10.
VUELINK connection-
Connects to the “black” end
of the VueLink interface
cable.
Attention symbol-Consult manual for
detailed information.
Power switch
Connection to VueLink module
Power jack

Rev. 00 Model 509 Service Manual 7
4Electronic Theory of Operation
The electronic theory of operation of the Model 509 Pulse Oximeter monitor is detailed
in the subsections below. See Schematics and Assembly Drawings on page 37. for
accompanying information.
4.1 2543 Main Board
4.1.1 Power Supplies and Voltage Reference
Refer to schematic sheet 3. Power for the monitor enters at J101 when SW1 is closed
(switched ON), the power is routed to the 2581 Power board through J102. Power then
returns to the board as an analog (V8.1) and a digital (VDD) supply. Diode D1 protects
against reverse bias, fuse F1 protects against over current conditions.
The LEDSRC supply which supplies the sensor’s LEDs is current regulated by IC2 and
further filtered by L3, C8 and C9. It is supplied by the analog supply V8.1 from the 2581
board. The VDD digital supply from the 2581 board is filtered by L2 which creates the
+VA supply. The -VA supply is created by IC3 which is a charge pump inverter. The +VA
and -VA supplies are needed by the bipolar analog circuits in the monitor.
Refer to schematic sheet 2. A positive reference voltage VREF2.5 is developed by IC8,
which is a +2.5 volts DC reference derived from the +VA supply. A negative reference
voltage is developed by IC23A (pin1) by inverting the +2.5 volt supply (schematic sheet
3). This negative reference is -VREF at TP6. The analog to digital converters IC9, IC10
and IC11use the VREF2.5, the -VREF (-2.5V DC) is used by the digital to analog
converter IC22.
4.1.2 Sensor LED Drive Circuits
See schematic sheet 2. When the RDLED signal goes low (logic 0), Q3 turns off and
the VLED signal is divided down by R23 and R25, at IC7A (pin 3). FET Q2 is in turn
driven on by IC7A (pin 1). Current will flow from LEDSRC (J200 pin 7) through the red
LED in the sensor, through Q2, then through R20 to ground.
When RDLED returns high (logic 1), Q3 is biased on, forcing IC7A pin3 to ground
potential, this results in 0 volts at the output of IC7A (pin 1). FET Q2 is biased off, and
as a result, the Red LED in the sensor is off.
The Infrared LED drive circuit operates in the same manner as the Red LED drive
discussed above. The IRLED signal activates Q4 which controls IC7B, this in turn
controls Q8. The source of Q8 will control the Infrared LED of the sensor.
Refer to schematic sheet 3. The VLED line voltage is derived from IC23B pin 7 which
is controlled by the Digital to Analog Converter IC22. When the DACCS line is brought
Low IC22 is enabled. The data on lines D0-D7 now control the output of IC22 which in
turn control IC23Bs output on pin 7(VLED).

4 Electronic Theory of Operation 2543 Main Board
8Model 509 Service Manual Rev. 00
4.1.3 Photodiode Return Path
Refer to schematic sheet 2. Light, from the sensor’s red or infrared LED, shines through
the pulsating vascular bed (the patient’s finger, toe, etc.) placed between the LEDs and
the photodiode. Some of this light emerges from the tissue and impinges on the
photodiode, causing the photodiode to conduct current. IC4B pins 5-7 are set up as a
differential amplifier that converts this input current to a voltage at the amplifier output.
The sensors are wired such that photodiode current produces a positive voltage at
IC4B pin 71.
The voltage at IC4B pin 7 is presented to an analog switch IC5B pin 6. This switch is
controlled at pin8 by INSIG (Input Signal), and will be closed (IC5B pins 6 and 7
connected) except if the monitor is in a probe off patient condition or is undergoing its
self-test at system power up. The switch IC5C pins 9-11, controlled from SIGND (Signal
Ground) will be open (no connection between IC5C pins10 and 11) except as noted
above for the switch at IC5B pins 6-8. As a result, the IC4B pin 7 voltage passe
undisturbed to the high pass filter consisting of R14 and C15.
The ASAMP signal is active whenever either sensor LED is turned on. This causes Q5
to turn off and the charge at C15 passes through to IC4A pin 3. The ASAMP line returns
to a logic high when neither LED is being driven, causing Q5 to turn on. With Q5
conducting, any charge at C15 is discharged to ground and the next pulse will charge
C15 from a known level. If it were not for Q5, any charge remaining on C15 from the
previous pulse or from ambient light reaching the photodiode would be added to the
charge from a new pulse—creating measurement errors.
If the signal at IC4A pin 1 is the product of the Red LED being turned on, then RDSAMP
will go low and close the switch at IC5A pins 2-3, thereby presenting the signal to a
sample and hold circuit consisting of R29 and C26 (that maintains the signal until next
sample pulse arrives), a gain stage, (IC6A), a filter network (C34 and R34), and finally,
to the red channel Analog-to-Digital Convertor (ADC) IC10.
If the signal at IC4A pin 1 is the product of the Infrared LED being turned on, then
IRSAMP will go low and close the switch at IC5D pins 14-15, thereby presenting the
signal to a sample and hold circuit consisting of R28 and C25 (that maintains the signal
until next sample pulse arrives), a gain stage, (IC6B), a filter network (C29 and R38),
and finally, to the infrared channel Analog-to-Digital Convertor IC9.
4.1.4 Calibrating the 20-Bit Analog to Digital Converters (ADCs)
The 20-bit ADCs are calibrated as part of the system self-test which occurs each time
the monitor is turned on. At power up, the microprocessor sets the CAL line high. The
system calibrations input SC1 is set high. The CS5503 ADC will not operate while the
CAL line is high. On the falling edge of the CAL signal, the ADC will initiate a calibration
cycle. The type of calibration is determined by the state of the SC1.
The high at SC1 causes INSIG to go high and reset SIGND to a logic low. The high
INSIG opens the switch at IC5B pin8 so that IC5B pins 6 and 7 are no longer
connected—disconnecting the returning photodiode signal from the rest of the circuitry.
The low SIGND signal closes the switch at IC5C pin9 and as a result, the input to the
C15-R14 high pass filter (and thus the entire ADC input circuitry) is brought to ground
potential.
The CAL line (which went high at power up) is reset low and ADCs IC9 and IC10 begin
their calibration cycles. Because the analog input circuitry is grounded via SIGND, only
circuit offset voltages can be present at the (pin 9 AIN) inputs. The calibration cycle sets
1. The Model 509 uses SuperBright™ sensors. If a non-SuperBright™ sensor is connected, IC4b pin 7 will go negative.

2543 Main Board Electronic Theory of Operation 4
Rev. 00 Model 509 Service Manual 9
the ADC “zero” point to equal this voltage, thus compensating for any circuitry offsets.
The ADC then sets its “full scale” point to equal the voltage at its VREF (pin 10) input.
This completes the calibration cycle.
The ADC can now start sampling its input and converting it to a 20-bit digital word. The
processor resets SC1 to a logic low, causing IC5C pin9 to open and IC5B pin8 to close.
The photodiode signal can now reach the ADCs.
4.1.5 20-Bit Analog to Digital Conversion
Refer to sheet 2 on schematic. Data from the red and infrared channels is sampled by
the 20-bit measurement ADCs, IC10 and IC9 respectively. The analog input at pin 9 is
converted to a digital representation with 20-bit resolution based on the input
magnitude.
The CS5503 converter continuously samples its input, converts the value to a digital
word, puts the word in its output buffer (overwriting previous buffer contents), then
repeats the process by again sampling its input. The frequency of the sample/convert/
overwrite-buffer sequence is based on the 3.072 MHz clock signal at the ADC pin 3
(F_ADCCLK) input.
The microprocessor starts a read cycle of the Infrared channel by bringing ADCIRCS
low. A Red channel read starts when ADCREDCS is brought low. On the falling edge
of these signals (CS lines), the output word’s MSB (most significant bit) appears at pin-
20 SDATA (Serial Data) output. The SDATA line connects directly to the
microprocessor’s serial input (RXS) pin. The remaining bits (in descending order) are
output from SDATA with subsequent falling edges of the Serial Clock (CLKS) input at
pin 19. The SDATA output automatically goes to a 3-state (high impedance) condition
after completing a word transmission, thus freeing the data line for other uses (i.e., the
other ADC channel).
The CLKS rate is significantly slower than the ADC sampling rate. As a result, the ADC
rewrites its output buffer with new information at a faster rate than the data can be read
from the buffer. No conflict occurs, however, because while CS is low (during the read
cycle), the ADC does not update its output buffer—the current word is not overwritten.
After the processor receives the entire word, it allows the convertor’s CS to return high,
and the ADC resumes its sample/convert/overwrite-buffer cycle.
4.1.6 Sensor Status
The microprocessor monitors several sensor parameters in addition to the red and
infrared data channels. These parameters allow the software to determine when
certain error conditions are present in order to display the proper error code.
Refer to schematic sheet 2. The 8-to-1 multiplexor, IC12, decodes the A0MUX-A2MUX
input address lines and connects one of eight status parameter inputs to the multiplexer
output at IC12 pin 3. Resistor R47 and diode D13 prevent negative voltages from
reaching the input of IC11.
IC11is an 8-bit serial analog-to-digital convertor. While theIC11 Chip Select ( ADC3CS)
input is high, the CLK input and DOUT output are in 3-state mode. When ADC3CS is
brought low (under processor control), the most significant bit (D7) of the previous data
conversion becomes available at the DOUT pin. The remaining bits (D6-D0) are shifted
out on subsequent falling edges of the CLK input. On the clock pulse following the one
that shifts out the least significant bit (D0), the CLK and DOUT lines are returned to 3-
state and IC11 performs a new conversion based on the input it receives from the IC12
channel selected by the A0MUX-A2MUX input address lines.

4 Electronic Theory of Operation 2543 Main Board
10 Model 509 Service Manual Rev. 00
The IC11 sample/convert/store-result cycle is based on internal chip timing and not the
CLKS input which (along with ADC3CS) only controls serial data output. Thus the CS
line is free to return high once the IC11 cycle begins.
4.1.7 Sensor Status Parameters
The sensor status parameters input to the multiplexor IC12 are described below.
ADCVRD: This signal is not used as of this writing.
ADCVIR: This signal is not used as of this writing.
ADCFEDC: Photodiode DC Level.
Resistors R11, R12 and capacitor C14 form a voltage divider and low pass filter that
provide a measure of the mean DC level at the output of the photodiode amplifier IC4B
pin 7. This signal (IC12 pin 15) is used in determining ambient light interference. If this
line is examined while the sensor’s red and infrared LEDs are turned off, then any DC
level at IC4B pin 7 must be the result of ambient light impinging on the photodiode. If
the DC shift is in excess of limits set in the software, a Light Interference message
appears on the monitor’s display.
ADCLPWR: Sensor LED Supply Voltage.
This channel, at IC12 pin 12, monitors the sensor LED supply voltage through a voltage
divider consisting of R2 and R3 (sheet 3 on schematic). If a fault occurs that causes the
LED supply fuse F2 to blow, or if the sensor wires are shorted, this channel reports the
condition and the monitor will indicate the appropriate error condition.
ADCIRLED: Infrared LED Cathode Voltage.
A low pass filter/divider consisting of R17, R18 and C24 provides a means to measure
the cathode voltage of the sensor’s Infrared LED. When the channel at IC12 pin 5 is
sampled the monitor can determine if the LED is open circuit (zero volts at IC12 pin 5)
or operational (approximately 2.5 volts at IC12 pin 5).
ADCRDLED: Red LED Cathode Voltage.
A low pass filter/divider consisting of R15, R16, and C23 provides a means to measure
the cathode voltage of the sensor’s Red LED. When the channel at IC12 pin 4 is
sampled the monitor can determine if the LED is open circuit (zero volts at IC12 pin 4)
or operational (approximately 2.5 volts at IC12 pin 4).
4.1.8 Processor and Memory
Refer to page 1 on schematic. The Model 509 is controlled by IC14, an 8 bit
microprocessor running at 6.144 MHz. Crystal Y1 (12.288 MHz) controls the operating
frequency, system address lines are labelled as A0-A17, and system data lines are
labelled D0-D7.
The system program is contained in IC18, a 27C101 (1 MB) EPROM. When ROMCS
is brought low a read operation is performed on IC18. The ROMCS line is controlled by
the ME line (Memory Enable) and address line A17. When both the ME line and
address line A17 are low the ROMCS line will go low (IC20A pin 6), this enables the
data to be read from IC18.
System RAM is contained in IC17, a 256k SRAM. When both the RD and RAMCS lines
are brought low a read operation is performed on IC17. With both WR and RAMCS low
a write operation will be performed. The RAMCS line is controlled by the ME (Memory
Enable) line and address line A17. When address line A17 is brought high, and the ME
line brought low, IC20B pin 3 will go low activating the RAMCS line.
Refer to sheet 3 on schematic. The processor communicates to the Vuelink through
serial channel 0 on the microprocessor. The TX0 and RX0 lines from the processor are
converted to RS232 levels by IC13 as TXD0 and RXDI.

2543 Main Board Electronic Theory of Operation 4
Rev. 00 Model 509 Service Manual 11
4.1.9 Decoding
Refer to page 1 on schematic. A three to eight line decoder IC19, is used for decoding
various address, write, and I/O lines for the system. Address lines A4, A5, A6, and A7
along with the IOE and LIR lines will enable one of the Q outputs of IC19.
4.1.10 Processor Superviso
Refer to page 1 on schematic. A microprocessor supervisory integrated circuit, IC29
monitors the power supply, generates the Reset signals, and switches the power
supply to the SRAM over to battery on power down. The WDOG line under control of
the processor must be toggled before a specific time-out occurs (1.6 seconds)
otherwise the RESET line is brought low resulting in the system resetting itself.
Therefore, the processor toggles the WDOG line periodically to avoid the reset which
ensures that the processor is working and not lost in a loop or task. If the VDD supply
drops below a certain level (4.65V) the RESET line will also be brought low to reset the
system.
4.1.11 Front End Timing Signals
Refer to page 3 on schematic. A 14 stage divider IC27, acts as a timing sequencer. The
ADCCLK input is the clock input, the RESET line is the clear input, used for clearing
the chip at power up. The Q4-Q11 outputs of IC27 are divided down from the clock input
and feed IC28, the data sampling controller. The Q14 output of IC27 is used as an
interrupt that is generated roughly every 5 milliseconds (INT5MS).
The data sampling controller IC28 is a Programmable Electrically Erasable Logic
device (PEEL). The PEEL uses the outputs from IC27 and generates the front end
timing signals. These signals control the sensor LED drive and the photodiode’s return
path circuitry during normal operation and calibration.
The RESET and SC1 lines control when the outputs of IC28 are active, both these lines
must be low in order for IC28 to operate normally. The RESET line controls IC28 during
Name Function
DACCS
Digital to Analog Converter
Chip Select
This line will enable writing to IC22.
DISPC
Display Chip Select
This line enables the displays to be written to.
KEYLATCH This line enables the input latch that reads the
keypanel.
DAC2CS This line enables the D/A converter which controls
the audio output level.
PORT1WR
Port #1 Write
This line enables writing to IC16, which controls
the multiplexor lines, SC1 and CAL lines for the 20
bit A/D Converters, and all data converter chip
selects.
PORT2WR
Port #2 Write
This line enables writing to IC15 which controls the
20 bit A/D converter sleep line ADCSLP and the
ALERT line

4 Electronic Theory of Operation 2543 Main Board
12 Model 509 Service Manual Rev. 00
power up, while the SC1 line is under processor control and will toggle when a probe
off patient alert exists and during the power up self test.
4.1.12 System Output Ports
Refer to page 1 on schematic. There are two output latch chips IC15 and IC16, these
control various lines for system control. The first port IC16, enabled when PORT1WR
is high, controls the CSIO PEEL IC26, the analog multiplexor IC12, and selection of the
A/D converters. The second port IC15, enabled by the PORT2WR line, handles control
line ADCSLP and the ALERT line.
The output ports are selected by the decoding performed by IC19, IC20 & IC21 and the
WR line. The signals controlled by the ports are listed below with a brief description of
their function.
Signal Description
INSIG
Input Signal
This line will enable signals from the
photodiode, or prevent signals from the
photodiode from reaching the detection circuitry.
RDLED
Red LED
Controls the signals for the Red LED in the
sensor.
IRLED
Infrared LED
Controls the signals for the Infrared LED in the
sensor.
SIGND
Signal Ground
This is used to short out the inputs of the
detection circuitry so that the system can
compensate for offsets.
ASAMP
Analog Sample
This line is used to short out the capacitor used
in the sample and hold circuitry to avoid having
residual charge interfere with data sampling.
SYNC
Synchronization
Synchronization signal, not used in this system.
IRSAMP
Infrared Sampling
Used for sampling the Infrared signal response
from the photodiode.
RDSAMP
Red Sampling
Used for sampling the Red signal response from
the photodiode.
Signal Description
AA0-AA1 Decode line for selecting ADCs.
SC1 Used for 20 bit ADC calibration.
CAL De-activates the 20 bit ADCs prior to calibration.
A0MUX-A1MUX Selects one of six sensor status channels that will
be switched to the serial A/D converter for conver-
sion.
NEXT Used in decoding selection of ADCs.
ADCSLP ADC sleep line.
ALERT Alert line.

2581 Power Board Electronic Theory of Operation 4
Rev. 00 Model 509 Service Manual 13
4.1.13 Serial I/O Controller
Refer to page 1 on schematic. Digital data from the three Analog-To-Digital Convertors
SDATA is read by the CPU through its clocked serial data input (RXS) at IC14 pin 56.
The PEEL IC26 acts as the Clocked Serial Input/Output (CSI/O) Controller.
Except during power up or watchdog timer reset, IC27 pin 3 (sheet 3 on schematic)
provides an interrupt to the CSI/O controller in the form of a 5 millisecond period
square-wave input to IC26 pin 7 (INT5MS).
On the rising edge of INT5MS, a CPU interrupt request is generated when IC26 pin 18
(CPUINIT) goes low. The CPU responds by sending the clock input to CSI/O controller
(CKS) at IC26 pin 6 low. (This CKS line is inactive (high) unless a serial receive
operation is in progress.) The CPU also sets up the ADC decode lines AA1 and AA0 at
IC26 pins 5 and 4, and as a result, one of the ADC chip select lines (ADCIRCS,
ADCREDCS, ADC3CS) is brought low, and the CPUINIT line is disabled.
On the rising CKS signal a CLKS output pulse at IC26 pin 14 is sent as a serial clock
input to the ADC selected by the decode lines. Decode results are shown below.
Successive CKS/CLKS pulses cause the ADC data to be shifted out of the ADC (most
significant bit first) along the serial data line (SDATA) to the CPU serial input (RXS) at
IC14 pin 56.
After receiving the correct number of bits for the ADC being read, the CPU changes the
AA1 and AA0 decode lines and exerts the Next line (NEXT) at IC16 pin 12 low. This
restarts the serial data shifting out of the newly selected ADC.
After all three ADCs have been read, the CPU sets the AA1 and AA0 decode lines to
exert the internal TEND signal and set the 8-bit ADC to the next channel (so that it has
time to settle before the next read of the ADC). This re-enables the CPUINIT line. At
this point the CSI/O controller is reset awaiting an INT5MS pulse to begin the cycle
again.
4.1.14 Audio Drive Circuitry
Refer to page 3 on schematic. Audible tones are generated by the Digital to Analog
Converter IC24 when both the WR and DAC2CS are low. The output of IC24 drives
non-inverting amplifier IC25B which in turn drives Q7. Transistor Q7 boosts the current
of IC25B in order to drive transducer LS1.
4.2 2581 Power Board
Power from the external supply enters the board as VRAW through J1 and is converted
to a digital supply (VCC) by voltage regulator IC2 and an analog supply (V8.1) b
voltage regulator IC1. The analog supply is used as the supply for the LEDs in the
sensor (LEDSRC) and is also used by the audiocircuitry. The digital supply, in addition
to supplying the digital circuitry is converted to bipolar supplies for some of the analog
circuitry in the monitor
AA1 AA0 Decode
00Red LED 20-bit ADC
01Infrared LED 20-bit ADC
11Sensor Status 8-bit ADC
10Internal CSI/O signal (TEND)

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4.3 2542 Display Board
The display board contains two three digit LED displays and the keypanel latch. The
front keypanel connects to J203 and the main board connects through J202. Two
LEDS, one for power indication and the other for the alert icon are also located on the
display board.
Address line A2 controls which of the two displays is currently selected while address
lines A0 and A1 determine which digit of the selected display is being written to by the
processor’s data lines D0-D7. The WR and DISPCS lines also control the selection of
the displays (IC2 and IC3). The combination of RP1 pins 1and 6, R3 and Q1 inverts the
A2 signal for IC3, this enables A2 to either select IC2 or IC3 by changing states (this is
in accordance with the WR, DISPCS and RESET lines).
The ALERT line draws current through LED D1 when low, this illuminates the display’s
alert icon (red). When power is applied to the monitor LED D2 illuminates green.
The membrane keypanel is decoded by IC1. The KEYLATCH line enables IC1 b
polling it to check if any of the four front panel keys has been depressed. The
appropriate output from IC1 is read by data lines D0-D3 (remaining lines are not
necessary and are tied to ground).