Model 710 and 715 Capnograph and Oximeter Service Manual Dec 2000

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Model 710/715 Service Manual



 General Description ...1 Indication for use ...1 Keypanel Controls and Indicators ...1 Connections and Labeling ...3 Principle of operation ...4 Theory of Operation ...5 Digital Control System ...5 CO2 System Analog Subsections ...11 Saturation Analog Subsections ...15 Power Supply and Battery Charger ...18 Functional Tests ...21 Equipment Required ...21 Procedure ...21 Accuracy Tests ...27 Equipment Required ...27 Procedure ...27 Electronic Tests ...31 Equipment Required ...31 Test Procedure ...31 Safety Testing ...33 Maintenance ...35 General ...35 Maintenance Schedules ...35 Cleaning and Sterilization ...35 Battery Maintenance ...38 Maintenance Schedules ...38 Assembly Exchanges ...39 Serial Communications/Power Interface Connector ...42 Software Update Instructions ...42 Status Messages ...45 System Messages ...45 Capnography Messages ...45 Oxygen Saturation Messages ...47 Specifications ...49 General ...49 Capnograph ...49 SpO2 Section ...50 Pulse Rate Section ...50





Model 710/715 Sevice Manual



Monitor Specifications ... 51 Additional Features ... 51 Accessories ... 53 Parts ... 57 Drawings and Schematics ... 61

Model 710/715 Service Manual



% For maximum patient and operator safety, you must follow the following warnings and cautions.





 

         



 

• Explosion Hazard: DO NOT use TIDAL WAVE Sp in the presence of flammable anesthetics. Use of this instrument in such an environment may present an explosion hazard. • Electrical Shock Hazard: Always turn TIDAL WAVE Sp off and remove any external devices before cleaning it. Refer servicing to qualified service personnel. • Failure of Operation: If the monitor fails to respond as described, do not use it until the situation has been corrected by qualified personnel. • Do not operate TIDAL WAVE Sp if it appears to have been dropped or damaged. • Do not operate TIDAL WAVE Sp or its accessories when it is wet due to spills or condensation. • Never sterilize or immerse the monitor, sensor or accessories in liquids. • The monitor does not alert for NO RESPIRATION if the airway adapter is removed from the CAPNOSTAT CO2 sensor. • Verify the “No Resp Timer” setting prior to use. • Do not position any sensor cable in a way that may cause entanglement or strangulation. • The TIDAL WAVE Sp is not intended to be used as a primary diagnostic apnea monitor and/or recording device. • Patient Safety: Care should be exercised to assure continued peripheral perfusion distal to the SpO2 sensor site after application. • Inspect the SpO2 sensor 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. • Data Validity: As with all pulse oximeters, inaccurate SpO2 and Pulse Rate values may be caused by: Incorrect application or use of 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 those with a xenon light source, or direct sunlight; Excessive patient movement; Venous pulsations; Electrosurgical interference. • The external battery charger should NOT be used to recharge the battery near or in close proximity to patients and/or other medical equipment in operation. It is intended for use in service areas only (i.e. nurses station, biomed lab, etc.). • Connection of an external device (e.g. printer or computer) to the RS232 serial port on the BaseStation may compromise patient safety.





Model 710/715 Sevice Manual







                • Federal (U.S.A.) law restricts this device to sale, distribution, or use by or on the order of a licensed medical practitioner. • Use only an external power supply approved by Novametrix for use with this device. Use of any other power supply may damage the TIDAL WAVE Sp and void the warranty. • Do not operate TIDAL WAVE Sp or its accessories when it is wet due to spills or condensation. • Do not operate TIDAL WAVE Sp if it appears to have been dropped or damaged. • Keep TIDAL WAVE Sp and its accessories clean. • Inspect the integrity of the TIDAL WAVE Sp and its accessories prior to use. • Never sterilize or immerse the monitor, sensor or accessories in liquids. • Do not sterilize or immerse sensors except as directed in this manual. • Do not apply excessive tension to any sensor cable or pneumatic tubing. • Do not store the monitor or sensors at temperatures less than 14°F (-10°C) or above 131°F (55°C). • Do not operate the monitor or sensors at temperatures below 50°F (10°C) or above 104°F (40°C). • If a Single Patient Use Sampling Adapter becomes occluded, replace and discard the adapter. • It is recommended that the CAPNOSTAT CO2 sensor be removed from the circuit whenever an aerosolized medication is delivered. This is due to the increased viscosity of the medications which may contaminate the sensor windows, causing the sensor to fail prematurely. • Where electromagnetic devices (i.e. electrocautery) are used, patient monitoring may be interrupted due to electromagnetic interference. Electromagnetic fields up to 3V/m will not adversely affect system performance. • Refer servicing to qualified personnel.







                

 

• The TIDAL WAVE Sp monitor is intended for operation with Novametrix Single Patient Use airway adapters. • Operating the TIDAL WAVE Sp below 50°F (10°C) will result in longer warm-up time and reduce battery life. • Components of this product and its associated accessories which have patient contact are free of latex. • Certain rebreathing circuits, or the presence of artifacts such as cardiogenic oscillations, may cause TIDAL WAVE Sp to react to non-respiratory CO2 fluctuations as if they were breaths. This condition affects only the RESP numerical displays; the capnogram display continues to provide an accurate picture of the CO2 waveform. • After the life cycle of our equipment and all accessories has been met, disposal of the equipment should be accomplished following the national requirements. Contact the local Novametrix representative for questions concerning disposal.

Model 710/715 Service Manual



& 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. Service Department For factory repair service, call toll free 1-800-243-3444 In Connecticut, call Collect (203) 265-7701 Facsimile (203) 284-0753 World Wide Web: http://www.novametrix.com Internet: [email protected] Caution: Federal (U.S.A.) law restricts this device to sale, distribution, or use by or on the order of a licensed medical practitioner. Novametrix manufacturing facility is certified to ISO 9001 and EN46001 (MDD93/42/ EEC Annex II). Novametrix Medical Systems Inc. products bear the “CE 0086” mark. The product is certified by Underwriter’s Laboratories (UL) to bear the UL mark; certified by TUV Rheinland to IEC601-1 (EN60601-1). TIDAL WAVE Sp and CAPNOSTAT are registered trademarks and Y-Sensor, SuperBright and OxySnap are trademarks of Novametrix Medical Systems Inc. Cidex is a trademark of Arbook, Inc. Models 710 and 715 are Year 2000 compliant. Copyright 1999, 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.





Model 710/715 Sevice Manual



% 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 800243-3444, or 203-265-7701; by facsimile at 203-284-0753; or, by e-mail at [email protected]. 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 “nonwarranty” 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 call Technical 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 onsite 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.

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General Description

1.1 Indication for use The Model 710 and Model 715 TIDAL WAVE Sp handheld, portable Capnometer/Oximeters are intended to be used for monitoring end tidal CO2, respiration rate, functional oxygen saturation and pulse rate in monitoring environments such as ventilatory support, emergency and anesthesia. The Model 715 incorporates a miniature vacuum pump to draw expired respiratory gases through the CAPNOSTAT CO2 Sensor using a sampling airway adapter and nasal cannula. TIDAL WAVE Sp is designed to monitor adult, pediatric and neonatal patients. TIDAL WAVE Sp is not intended for any other purpose.       

 

    

 

      

1.2 Keypanel Controls and Indicators

Page key

Display screen

Power key

Alert key

Backlight key

Adapter key

Battery charge indicator and LED

AC indicator Alert LED

CONTROLS Switches power on/off. With monitor ON, press and hold the POWER key to enter the MONITORING MODE selection menu. Sets display screen to Data Display, EtCO2 waveform, plethysmogram, EtCO2 trend or SpO2 trend. Press and hold to enter the PRINT SELECTION menu (with printing enabled).

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General Description

Sets 2 minute silence and displays SET ALERTS menu (3 s timeout). 2 minute silence: icon illuminates. Press again to cancel. Press and hold for 3 seconds to disable audible alerts: icon flashes. Press and hold again to cancel. The Alert Key LED will display the following: Steady yellow: audio silenced for 2 min., no alert in progress. Flashing yellow: audio silenced (no alert in progress). Flashing red/yellow: alert in progress; audio is off or 2 minute silence. Sets adapter type. Press and hold for 4 seconds to zero an adapter. Turns backlight on/off, or press and hold to adjust contrast. Lit when the unit is on battery power. Green; battery is fully charged, slow flashing yellow; battery power is low, Fast flashing red; battery is exhausted. Green when the monitor is connected to an AC power source. ICONS Audible alerts silenced. Audible alert silenced for two minutes. Alert limits disabled. Select ENABLED or DISABLED in the CONFIGURATION menu. Indicates adapter key. Set time/date. Press and date.

from the CONFIGURATION menu to set time

Indicates backlight key. Displayed beside any Trend screen. Sensor not up to temperature icon. Displayed when performing an adapter zero and the sensor is not at operating temperature. CO2 detected icon. Displayed when selecting an adapter zero and the monitor detects breaths. Pulse detected icon. Displayed when SpO2 sensor is attached to patient and the monitor detects a pulse. Breaths detected icon. Displayed when CAPNOSTAT CO2 sensor is attached to patient and breaths are detected.

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General Description



1.3 Connections and Labeling DB-9 SpO2 sensor connection

Sampling system input Sampling system output Endview Model 710

Endview Model 715 CO2 sensor connection DC input Rearview Model 710/715

Sideview Model 710/715

RS232 connection and external power input from BaseStation

Battery compartment

SYMBOLS Patient isolation: Identifies connection as type BF

Attention: Consult manual for detailed information Sampling System: Gas output Sampling System: Gas input DC input. Connect external power supply to this port. Use only Novametrix external power supply, Catalog number 9220-10. Recyclable item. This symbol is found on the internal battery and should not concern the common user. Refer to qualified service personnel when battery replacement is required. Separate collection. Appropriate steps must be taken to ensure that spent batteries are collected separately when disposed of. This symbol is found on the internal battery and should not concern the common user. Refer to qualified service personnel when battery replacement is required.

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General Description

1.4 Principle of operation CO2 TIDAL WAVE Sp uses the CAPNOSTAT CO2 sensor to measure CO2 by using the infrared absorbtion technique, which has endured and evolved in the clinical setting for over two decades and remains the most popular and versatile technique today. The principle is based on the fact that CO2 molecules absorb infrared (IR) light energy of specific wavelengths, with the amount of energy absorbed being directly related to the CO2 concentration. When an IR beam is passed through a gas sample containing CO2 , the electronic signal from the photodetector (which measures the remaining light energy) can be obtained. This signal is then compared to the energy of the IR source and calibrated to accurately reflect CO2 concentration in the sample. To calibrate, the photodetector’s response to a known concentration of CO2 is stored at the factory in the monitor’s memory. A reference channel accounts for optical changes in the sensor, allowing the system to remain in calibration without user intervention.

SpO2 The TIDAL WAVE Sp determines oxygen saturation using sensors that contain red and infrared (660 and 940 nanometer) light sources, called light emitting diodes (LEDs). The light energy from each LED is beamed through a tissue sample-a pulsating vascular bed such as the patient’s finger or toe. The remaining light energy not absorbed by the tissue sample reaches a photodiode light receptor in the sensor. Oxygen saturated blood absorbs different amounts of light at each wavelength as compared to desaturated blood. Therefore, the amount of light absorbed by the blood in each pulse can be used to calculate oxygen saturation. The TIDAL WAVE Sp is calibrated to display “functional” saturation. This differs from the “fractional” saturation value displayed by most co-oximeters. Functional saturation is defined as:

Functional Saturation =

HbO2 100 - (COHb + METHb)

HbO2 = Fractional Oxyhemoglobin COHb = Carboxyhemoglobin METHb = Methemoglobin This can be considered to represent the amount of oxyhemoglobin as a percentage of the hemoglobin that can be oxygenated. Dysfunctional hemoglobins (COHb and METHb) are not included in the measurement of functional saturation. Pulse Rate is calculated by measuring the time interval between peaks of the infrared light waveform. The inverse of this measurement is displayed as pulse rate. The oxygen saturation and pulse rate values are updated once each second. Presence of a pulse is indicated visibly by a plethysmogram graphic display and audibly by a “beep,” when configured. The TIDAL WAVE Sp must be used in conjunction with SuperBright™ Sensors.

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Theory of Operation

The Tidal Wave Sp™ is a microprocessor based handheld instrument that measures the clinical parameters of CO2 production, respiration rate (RR), oxygen saturation (SpO2), and pulse rate. The electronic theory of operation of the Tidal Wave Sp is explained in detail in the subsections that follow. The Model 715 is equivalent to the Model 710 with the exception that the Model 715 has a sidestream sampling option.

2.1 Digital Control System Refer to 2752-03 schematic sheet 1. Embedded control for the system is provided by IC1, a Motorola MC68332 integrated microcontroller. In addition to a full 32-bit Central Processing Unit (CPU), this device also contains circuitry for system clock generation, peripheral chip select generation, data control, interrupt generation, a sophisticated timing coprocessor, synchronous serial communication and asynchronous serial communication. In general, functional signals are grouped together into ports, and each signal can be independently programmed by software to be its predefined port function or as discrete I/O. Additionally, the functionality for several ports (Port C, E and F) can be predefined by the state of the data bus on system power-up. A special “background mode” port allows the device to be controlled by an external source for system debugging and testing. Also integrated on-chip are several activity monitors, as well as a software watchdog to ensure proper device and system operation. Refer to table 1. Table 1: CPU Port Functions

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Port

Defined Function

TPU 16 Channels

Timing Signal Generation

Functionality Control , Data Bus Control (Alt Functions: D pulled low) Each channel independently user programmable as TPU function or as Discrete I/O

Serial Communications Port: QSM 4 Synchronous Serial QSPI: Queued Serial Peripheral Interface Chip Selects & one asynchronous serial SCI: Serial Communications Interface channel

QSPI chip selects independently user programmable, can be used as Discrete I/O or decoded to create up to 16 chip selects. SCI transmit can be programmed as Discrete I/O

Background Mode

Allows an appropriate external device to control the microprocessor and system

System debugging

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Theory of Operation

Table 1: CPU Port Functions C

Chip Selects

D0: CSBOOT* data width, 8 or 16bit D1: CS1*-CS3* or BR*,BG*,BGACK* D2: CS3*-CS5* or FC0-FC2 D3-D7: CS6*-CS10* or A19-A23

E

Bus Control

D8: Control Signals or discrete I/O

F

MODCK and Interrupts

D9: MODCK & IRQ or discrete I/O

The maximum operating frequency of the integrated processor is 20.97 MHz. The operating frequency is software selectable and generated by an internal VCO operating from Y1, a 32.768KHz watch crystal. The Timing Processor Unit (TPU) coprocessor of the MC68332 provides timing generation derived from the system clock. This feature is utilized to control the precise timing required for the acquisition of the end tidal carbon dioxide (EtCO2) and the oxygen saturation (SpO2) signals. The TPU is also use to generate the PWM (Pulse Width Modulation) control for the CAPNOSTAT CO2 sensor case and detector heaters, as well as to provide the frequency generation for the audio tones. See Tables 2 & 3. Table 2: TPU Timing Generation for the EtCO2 subsystem Signal Name

6

Description

Function / Timing

CO2AZ

Auto Zero

Clears the sample/hold circuitry prior to data acquisition. Active high, 2.84 ms

CO2PWENB

Pulse Width Enable

Defines the active time for both phases of the bipolar source pulse, used for pulse width protection circuitry. Active high, 830 µs

SRCDRV0

Source Drive 0

First source drive signal. Active high, 405 µs

CS*/H

Current Sample/Hold

Enables circuitry for source current measurement. Sample is taken when SRCDRV0 is active. Low = sample, 270 µs, High = hold

SRCDRV1

Source Drive 1

Second source drive signal delayed for 30 microseconds after SRCDRV0 ends. Active high, 395 µs

SS*/H

Signal Sample/Hold

Enables circuitry for CO2 and reference channel data acquisition. Low = sample, 270 µs, High = hold

CASEPWM

Case Heater PWM

PWM control for the case heater servo

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Table 2: TPU Timing Generation for the EtCO2 subsystem DETPWM

Detector Heater PWM

PWM control for the detector heater servo

TONE

Audio Tone Generation

Variable frequency outputs to generate system audio

CASEOT

Case Heater Over Temperature

Case heater over temperature shut down

DETOT

Detector Heater Over Temperature Detector heater over temperature shut down

Table 3: TPU Timing Generation for the SpO2 subsystem Signal Name

Description

Function / Timing

ASAMP*

Auto Zero

Clears the sample/hold circuitry prior to data acquisition. Active low

RDLED*

Red channel LED control pulse

Defines the active time for the red LED

IRLED*

Infra-red channel LED control pulse

Defines the active time for the Infra-Red LED

RSAMP*

Red channel sample/hold

Enables circuitry for the red channel signal measurement. Sample is taken when SRCDRV0 is active. Low = sample, 20 us, High = hold

ISAMP*

Infra-red channel sample/hold

Enables circuitry for the infrared channel signal measurement. Sample is taken when SRCDRV0 is active. Low = sample, 20 us, High = hold

Ferrite and L-C filters, 100pF capacitors, and 100 ohm resistors have been placed on selected microprocessor signals with fast rise and fall times (including timing, clock, and address & data lines) in order to help reduce and suppress the radiation of electromagnetic interference and decouple unwanted power supply noise. In addition, good EMI/EMC design techniques have been incorporated in the component layout and printed circuit board layout and manufacture. Table 4 lists the chip select, control and discrete I/O functions for the Tidal Wave Sp system module. On power-up, Ports E and F are programmed as discrete inputs by pulling down their controlling data lines, DB8 and DB9. After power-up, the software sets up each pin function individually and performs a series of self tests to check the integrity of the system. The state of configuration inputs on Port E (TST*, CNFG0*, CNFG1*, and CNFG2) are read. These inputs allow the software to identify different operating states such as Test Mode, or different hardware configurations. After the initialization period is complete and all system functions have been set,

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Theory of Operation

the LED output (PF0) toggles at a 1Hz rate switching transistor Q3 which drives the status LED D3, indicating that the system is ready for operation. Table 4: Chip Select, Control and Discrete I/O Port C

Pin Functions

I/O

Comments

D0 pulled low, D1-D7 pulled high, pins are chip select on power-up CSBOOT*

8

System Signal Name

O

Program PROM chip select byte wide mode, (8-bits) D0 = LOW

CS0* / PC0 / BR* SRAMWR*

O

SRAM write enable

CS1*/ PC1 / BG*

AUD_CS*

O

Audio attenuation control chip select

CS2* / PC2 / BGACK*

SRAMRD*

O

SRAM read enable, byte mode

CS3* / PC3 / FC0 ROMWR*

O

FLASH PROM Write Enable, Byte Mode

CS4* / PC4 / FC1 DISPCS1*

O

LCD chip select #1

CS5* / PC5 / FC2 DISPCS2*

O

LCD chip select #2

CS6* / PC6 / A19 LATCH1_CS*

O

System control signals latch 1 chip select

CS7* / PC7 / A20 LATCH2_CS*

O

System control signals latch 2 chip select

CS8* / PC8 / A21 ROMWREN

O

Port C discrete output, prevents unintentional writes to FLASH EPROM. This signal must be asserted before ROMWR* in order to overwrite the flash.

CS9* / PC9 / A22 PROFILE*

O

Enables software profiling data output latch

CS10* / ECLK / A23

O

Enable clock for the liquid crystal display

Model 710/715 Service Manual

ROMOE*

ECLK

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Theory of Operation

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Table 4: Chip Select, Control and Discrete I/O E

F

D8 pulled low, discrete I/O on power-up DSACK0* / Port E0

TST*

I

Initiate system TEST if low

DSACK1* / Port E1

DS1*

I

Data and size acknowledge 1*

AVC* E2

/ Port

CNFG0*

I

Configuration switch 0

RMC* E3

/ Port

CNFG1*

I

Configuration switch 1

DS* E4

/ Port

DS*

O

Data strobe

AS*

/ Port E5 AS*

O

Address strobe

SIZ0*

/ Port E6 CNFG2*

I

Configuration switch 2

SIZ1*

/ Port E7 SLP*

I

SpO2 A/D converter sleep signal

R/W*

WR*

O

Data write strobe

MODCK / Port F0 LED

O

LED CPU activity Indicator

IRQ1*

/ Port F1 SW1

I

Keypanel switch 1 input

IRQ2*

/ Port F2 SW2

I

Keypanel switch 2 input

IRQ3*

/ Port F3 SW3

I

Keypanel switch 3 input

IRQ4*

/ Port F4 SW4

I

Keypanel switch 4 input

IRQ5*

/ Port F5 PWRKEY

I

Power key status input

IRQ6*

/ Port F6 EXTDCIN

I

Indicates external AC mains power operation

IRQ7*

/ Port F7 NMI

I

Non-maskable interrupt

D9 pulled low, discrete I/O on power-up

Background Mode Debugging External system debugging is possible by connecting an appropriate device (emulator or debugger) to header J401 and momentarily bring the BERR* (J401/2) low. This halts the bus activity and turns control of the system over to the external device. In this mode, internal MPU registers can be viewed and altered, special test features can be invoked and system memory can be read and written to.

System Memory An 8-bit wide data path is used for FLASH PROM and SRAM transfers. Program code storage is contained in a 1-Meg 5V FLASH or EEPROM (IC2) device. The FLASH PROM is protected from unintentional overwrites of the program code by transistor Q1 and the ROMWREN signal. The ROMWREN line must be high prior to writing new code into the FLASH devices. Nonvolatile data storage is contained in the 1-Meg SRAM (IC3). The SRAM is backed-up to retain it’s contents by applying a voltage on VBACKUP generated by BT1 (a 3.0V lithium battery) when power is off or the battery is removed from the monitor. During the battery backup state, transistor Q2 keeps the CS1* control of the SRAM in the inactive state. This forces the data bus to a high impedance state, isolating the SRAM from the rest of the system. True

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Theory of Operation

nonvolatile storage for the bootstrap parameters for the CAPNOSTAT CO2 sensor are stored in a serial EEPROM (IC2) located on the Interface (2753) board.

Serial Communications Refer to 2752-03 schematic sheet 6. The on-chip (IC1) asynchronous serial communications interface (SCI) channel is contained in the MC68332. The signals are level shifted to standard RS232 levels by IC26 which is a Dual RS232 Communications Driver/Receiver. The transmitters in the RS232 level shifter are under software control to minimize the patient leakage current to the rear panel connector (J101) when communication is not active. The signal COMMPWR controls the transmitters operation and is derived from IC9 pin 14 (schematic sheet 2). The serial connection to external, nonpatient contact devices is electrically isolated from the patient through the CAPNOSTAT airway adapter and the SpO2 sensor membrane interface. This connector, J101 is located on the rear panel and is designed to interface with external devices (i.e. computer, printer) when placed in a base station which contains the mating connector. In addition there is a 4 pin connector (J403) available for test and service which offers an internal connection to the serial communications at a TTL level. The data signals ASRxD and ASTxD are logic level signals and are diode protected against over voltage by D22 and D23 should IC26 breakdown from ESD (schematic page 6). Refer to Table 5 for the pinout and signals of serial interface connector J101. Table 5: Power/Communications 6-pin modular connector J101 located on the rear panel. Pin Number

Signal

Function

1

RxD

Internal MC68332 UART Receive, RS232 Signal, Level Shifted

2

TxD

Internal MC68332 UART Transmit, RS232 Signal, Level Shifted

3

DGND

Digital Ground

4

DGND

Digital Ground

+VCHG

External DC input supply to power unit and battery charger

5 6

User Interface Control Circuitry Refer to 2752-03 schematic sheet 2. The user interface features a 64 row by 128 column Liquid Crystal Display (LCD) module with an LED backlight. A 5-switch membrane keypanel is provided for operator entry. The user interface also contains three LED’s which represent various system conditions. Control of the user interface is provided by the LATCH1_CS* chip select signal together with the Port F input signals from the microprocessor. SW1-SW4 are inputs which read in the present state of the membrane keys. Depressing a key causes the signal line to be pulled low in contrast to its normally high state. IC9 provides a latched output for controlling the status LED’s. The LCD backlight is a series of LED’s which are driven by a 5.12kHz clock signal in order to lower the LCD backlight power requirement and is activated by the backlight membrane key. The LITE_CLK signal is a 5.12kHz logic level signal generated by IC7 (sheet 7) which modulates the LED backlight through FET switch Q4 (BKLGHT_OUT) when asserted by IC10 (BACKLIGHT). This signal is capacitively coupled by C42 in order to prevent the backlight from remaining on in the event of a system failure.

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Contrast control for the LCD is provided by DAC IC33 (sheet 6) and amplifier IC34A and transistor Q18 (schematic sheet 6). When the CPU detects a press and hold of the backlight membrane key, the CPU sends a digital ramp input to the DAC which causes the output to change accordingly. Inverting amplifier IC34A controls the base current into transistor Q18, which changes the level of the display contrast voltage, VDISP. Refer to schematic sheet 6. An audio frequency tone is generated by the TPU (Time Processor Unit) of the MC68332 (TONE). This signal is fed into the divider network consisting of R183 and IC32. IC32 is a 10k ohm E2 potentiometer whose value (when written to under software control) provides a means for attenuating the signal under CPU control. From the divider output the signal is amplified by IC34B and Q17 which drives the system speaker (LS1) to produce system audio. The AUD_EN line from IC9 controls Q19, when high the input to IC34B is grounded thus muting the audio.

Real Time Clock, Power on RESET Generation and Glue Logic Refer to 2752-03 schematic sheets 1 and 2. Time-keeping for date and time stamping of patient trend information is provided by IC8. This device contains a built-in crystal for precise time and date measurement. In the absence of digital power, the time keeping function is maintained by the battery backed supply, VBACKUP which is generated by the 3V lithium backup battery (BT1). On power-up, the system is forced into a “Reset” state by IC4 (sheet 1). When the supply voltage VDD, approaches 1V, the SRST* line is asserted to prevent undefined operation. IC4 also provides supervision over the VDD logic supply. If the logic supply falls below 4.55V ±120mV then IC4 generates a reset condition until the supply returns to a safe level. Inverter IC5 is used to generate the active high RESET signal. The Tidal Wave Sp makes use of the high level of integration offered by the MC68332. Therefore the glue logic required is a minimum. Chip selection for the serial peripherals is provided by decoding the queued serial module (QSM) (PCS0-PCS3) of the microprocessor IC1 (sheet 1 on schematic) using decoder IC12 (sheet 2) while parallel interface peripherals are selected by the internal chip select registers of Port C (BOOTCS* and CS0*:CS10*). Latch IC10 is used to control the saturation analog signal processing, the LCD backlight, the sidestream sampling pump (Model 715), and to power the monitor off.

2.2 CO2 System Analog Subsections CO2 Source Drive Refer to 2752-03 schematic page 3 and Table 2 of this document. The source drive circuitry is designed to drive the source with a bipolar signal to prevent the migration of charges within the source that may result from unidirectional electrical fields. The resistance of the source is monitored constantly to ensure the integrity of the system by sampling the current through the source while it is active. The SRCDRV0 and SRCDRV1 lines are used to control the bipolar signal that drives the source. The SRCDRV0 signal goes high as soon as the CO2AZ (Auto Zero) line goes low and the CO2PWENB (Pulse Width Enable) line goes high. The duration of SRCDRV0 is 405 us (microseconds), and drives the source in the positive direction. The SRCDRV1 line drives the source with an opposite polarity signal when high for the same duration. There is a 30 us delay from the time the SRCDRV0 line goes low to when the SCRDRV1 line goes high. This delay is

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to prevent the possibility of both SRCDRV0 and SRCDRV1 being active at the same time, thus creating a low impedance path between the two supplies (power supply shoot-through). SRCDRV1 steers current through the source in an opposite direction from SRCDRV0. When SRCDRV0 and CO2INH (Inhibit) are high, the output of MOSFET Driver IC13A pin 7 will go low. This turns the P-Channel half of MOSFET Q5 on. At the same time, the output of MOSFET Driver IC14B pin 6 will be high biasing on the N-Channel half of MOSFET Q6 on. With both Q5B P-Channel and Q6A N-Channel on, current will flow from +VSRC through Q5B to the positive source terminal, then back from the source negative terminal through Q6A, through R97 to -VSRC. When SRCDRV0 returns low, both Q5B and Q6A are turned off and no current flows through the source. After the 30 us delay, SRCDRV1 will go high. The output of IC14A pin 8 will go high, biasing the N-Channel section of MOSFET Q5 on. The output of IC13B pin 5 will go low, turning the P-Channel of Q6 on. Current will now flow from +VSRC through Q6B to the source negative terminal, back from the source positive terminal through Q5A and R97 to VSRC. Current will cease to flow when SRCDRV1 goes low. The bridge circuit of Q5 and Q6 in effect switches the polarity of the drive signal of the source between +VSRC and -VSRC. CO2PWENB also falls with the falling edge of SCRDRV1, signaling the end of source activity. When current flows through the source, it will also flow through current sensing resistor R97, creating a differential voltage proportional to the source current: VSRC = (VSR / RSR) * RS * AV(DA) where: VSRC = voltage out of difference amplifier proportional to current through the source element = 24V +/- 0.625V VSR =

differential voltage across the source element

RSR =

resistance of the source element

RS=

resistance of the current sensing resistor = 1 ohm

AV(DA)= difference amplifier gain = 5 VSRC = [120 (Volts*Ohms) / RSR] The voltage signal out of difference amplifier IC15B is level shifted through C52 and fed to the sample and hold IC16A via buffer amplifier IC15A. A low level on the CS*/H (Current Sample and Hold) signal allows the source current signal to be sampled. On the rising edge of CS*/H, the present voltage level of the source current signal is held and appears at the input to channel A2 of the Analog to Digital Converter IC6 (sheet 2 on schematic) for processing by the MPU. When CO2AZ is high, the input to the sample and hold of IC16A is grounded to discharge any residual charge that may be on C52. In order to prevent the source from being driven until the system is up and ready, there is protection circuitry that inhibits the source drive until enabled. During system power-up, the RESET line keeps Q7 on. This causes the CO2INH line to be brought low, preventing source pulses by pulling down SRCDRV0 and SCRDRV1 through D6. Protection circuitry also guards against extended pulse width as well as shortened duty cycle. On the rising edge of CO2PWENB, the trip point of IC17B is exceeded, allowing C55 to charge through R100. If the SRCDRV signals do not turn the Source Pulse off within 200 us after the 830 us pulse period, the trip point for IC17A will be exceeded, pulling the CO2INH line low turning the Pulse off. After the CO2PWENB signal returns low, capacitor C57 discharges through R101, keeping the output of comparator IC17B at the voltage acquired by C55. After approximately 10.4 ms, C57 will have discharged below the comparator trip point. The comparator output goes low, discharging C55 and the circuit is ready for the next source pulse cycle.

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