Mindray Datascope Trio Service Manual

S e r v i c e M a n u a l

S e r v i c e M a n u a l

Trio™ is a U.S. trademark of Mindray DS USA, Inc.

Velcro® is a registered trademark of Velcro Industries B.V.

Navigator™ is a U.S. trademark of Mindray DS USA, Inc.

Masimo SET® is a U.S. registered trademark of Masimo Corp.

Copyright © Mindray DS USA, Inc., 2008. All rights reserved. Contents of this publication may not be reproduced in any form without permission of Mindray DS USA, Inc.

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Table of Contents

Foreword.......................................................................................................................................................	iii
Warnings, Precautions And Notes ....................................................................................................................	iii
Warning........................................................................................................................................................	iii
Theory of Operation .........................................................................................................	1 - 1
Introduction....................................................................................................................................................	1	- 1
Hardware Overview .......................................................................................................................................	1	- 3
Power Supply Board (Lead Acid Battery) ....................................................................................................	1	- 3
Power Supply Board (Lithium Ion Battery)....................................................................................................	1	- 5
CPU Board (Main Control Board) ..............................................................................................................	1	- 6
Keypad Board.........................................................................................................................................	1	- 9
Keypad Board.........................................................................................................................................	1	- 10
Keypad Board.........................................................................................................................................	1	- 11
TR60-C Recorder .....................................................................................................................................	1	- 12
Serial Interface Converter Board .......................................................................................................................	1	- 14
Parameter Circuit Descriptions ..........................................................................................................................	1	- 15
ECG ......................................................................................................................................................	1	- 15
Respiration .............................................................................................................................................	1	- 15
NIBP ......................................................................................................................................................	1	- 16
SpO2 .....................................................................................................................................................	1	- 16
Temperature............................................................................................................................................	1	- 17
IBP (optional) ..........................................................................................................................................	1	- 17
Calibration/Maintenance ..................................................................................................	2 - 1
Calibration Introduction ...................................................................................................................................	2	- 1
Warnings and Guidelines................................................................................................................................	2	- 1
Test Equipment and Special Tools Required........................................................................................................	2	- 1
Calibration and System Checks ........................................................................................................................	2	- 2
Device Appearance and Installation Checks................................................................................................	2	- 2
Maintenance Menu..................................................................................................................................	2	- 2
Safety Tests.............................................................................................................................................	2	- 11
Testing Each Parameter....................................................................................................................................	2	- 12
ECG and RESP........................................................................................................................................	2	- 12
NIBP ......................................................................................................................................................	2	- 12
SpO2 .....................................................................................................................................................	2	- 13
TEMP .....................................................................................................................................................	2	- 14
IBP.........................................................................................................................................................	2	- 14
Parts ................................................................................................................................	3 - 1
Exploded Views of the Trio Monitor...................................................................................................................	3	- 1
Parts Listing ....................................................................................................................................................	3	- 12
Repair Information ...........................................................................................................	4 - 1
Introduction....................................................................................................................................................	4	- 1
Single Temp Cable Assembly ...........................................................................................................................	4	- 10
ECG Cable Assembly......................................................................................................................................	4	- 10
Troubleshooting ..............................................................................................................................................	4	- 11
Module-level Troubleshooting ....................................................................................................................	4	- 11
Disassembly Instructions...................................................................................................................................	4	- 14
Tools Needed .........................................................................................................................................	4	- 14
Removal of the Front Housing....................................................................................................................	4	- 14
Removal of Display ..................................................................................................................................	4	- 14
Removal of Thermal Printhead Recorder......................................................................................................	4	- 14
Removal of PCB Chassis Assembly.............................................................................................................	4	- 15
Removal of Display Mounting Plate............................................................................................................	4	- 15
Replacement of 3V Lithium Cell Battery.......................................................................................................	4	- 15

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Table of Contents

Removal of Power Supply Assembly...........................................................................................................	4	- 15
Removal of PCB Chassis Rear Panel Plate ...................................................................................................	4	- 15
Removal of NIBP/IBP PCB Mounting Plate ..................................................................................................	4	- 16
Removal of Handle ..................................................................................................................................	4	- 16
ECG Cable ESIS and Non ESIS ........................................................................................................................	4	- 17
ECG Shielded Lead Wires ...............................................................................................................................	4	- 18
Trio Wall Mounts and Rolling Stand..................................................................................................................	4 - 20
Appendix .........................................................................................................................	5 - 1
System Alarm Prompts .....................................................................................................................................	5	- 1

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Foreword	Introduction

Foreword

This service manual gives a detailed description of the Trio Portable Patient Monitor, including, circuit descriptions, test procedures and a spare part listing. This manual is intended as a guide for technically qualified personnel during repair, testing or calibration procedures.

Warnings, Precautions And Notes

Please read and adhere to all warnings, precautions and notes listed here and in the appropriate areas throughout this manual.

AWARNING is provided to alert the user to potential serious outcomes (death, injury, or serious adverse events) to the patient or the user.

ACAUTION is provided to alert the user to use special care necessary for the safe and effective use of the device. They may include actions to be taken to avoid effects on patients or users that may not be potentially life threatening or result in serious injury, but about which the user should be aware. Cautions are also provided to alert the user to adverse effects on this device of use or misuse and the care necessary to avoid such effects.

ANOTE is provided when additional general information is applicable.

Warning

WARNING: The NIBP pneumatic test (specified in the EN 1060-1 standard) is used to determine if there are air leaks in the NIBP airway. If the system displays the prompt that the NIBP airway has air leaks, please contact the manufacturer for repair.

CAUTION: To ensure continued use of the Factory Defaults when the unit is powered off and on, save the Factory Defaults as the User Default Configuration after reassembly.

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Introduction	Warning

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1.0 Theory of Operation

1.1Introduction

The Trio portable patient monitor uses a parameter module as the basis for acquiring patient data. The results are transmitted to the main control board to process and display the data and waveforms. CPU board commands and status messages of modules are transmitted via databus. The structure of the entire system is shown in the figure below.

Medical Staff

Keyboard		Display		Recorder

				Main				Network
Power				control				interface
				board				(future)

ECG/RESP/TEMP		NIBP		SpO2		IBP

Patient

FIGURE 1-1 System Structure Diagram

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Introduction	Theory of Operation

As shown in the above figure, the four parameter modules execute real-time monitoring of NIBP, SpO2, ECG/RESP/TEMP and IBP through the use of blood pressure cuffs and patient cables. The patient data is transmitted to the CPU board for display. When required, data may be printed out via the recorder.

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Theory of Operation	Hardware Overview

1.2Hardware Overview

			TFT Display
			834 inchs
			800 X 600
			X14		X15
			J6
		X16
Main
		Power Supply PCB				J5
Power
Input			J3			J4
					J2

Battery

VGA interface

NET

Interface

Analog

output

Serial Coverter

J1

Serial

FAN

J2

P.C.B

interface

P5

Alarm

P1

LED

J9

A4(TFT_DIGTAL)

Key & Alarm P .C.B.

P2 (CRT)

P10

J7

J8

P3(FOR 9000

P12

VGA)

P7(BDM

Speaker

)

P11

Host P .C.B.

X

P13

1 Recorder Module

TO

P17 (FOR 509C)

X

P15

2

X4

P16

P14 P8

P6

P9

X

From J2

X4

3

Recorder P.S.

X5

X6

X7

X8

ECG/RES

SPO2

NIBP

IBP

P/TEMP

Module

P.C .B.

P.C.B.

X9

X10

X11

X12

TEMP

G EC

SPO2

NIBP

IBP

IBP Cable

TEMP

ECG

SpO2

Cuff

Sensor

Cable

Sensor

FIGURE 1-2 Connection Diagram

1.2.1Power Supply Board (Lead Acid Battery)

P/N 0671-00-0235

Trio power supply board specifications:

¥AC input voltage:100~250 VAC

¥AC input current: <1.6 A

¥AC voltage frequency: 50/60 HZ

¥Two-way output voltage: 5 V/12 V, normal working current is 1.5 A for 5 V, 2 A for 12 V

¥Two-way output voltage has functions of short-circuit, over-current and over-voltage protection

¥The power board has reset function

¥The power board can manage the charging process of lead-acid battery (12 V/ 2.3 AH). The charging time is 8 hours maximum.

NOTE:	Power Supply Board must be connected to resistive load to
	operate properly and avoid damage due to an overcurrent
	condition.

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Hardware Overview	Theory of Operation

5VDC-DC

converter

Voltage

test

AC

AC/DC

input

REC POWER

SOURCE

Power on/off

control circuit

Battery

and

Charging

12V output

Management

Circuit

FIGURE 1-3 Block diagram of Trio power supply board

Key Test Points

NO.	NAME	LOCATION	FUNCTION
1	Rectified voltage	C12	Primary rectified voltage, range: 107~354 V
2	RTN1	C12 negative	Primary ground
		electrode
3	Driving	Q1.1	There is a driving waveform of about 100 KHZ
	waveform		between Q1.1 and the negative electrode of C12
4	VIN	C19 positive	17.5 V provide input voltage for DC-DC
		electrode
5	GND	C19 negative	Secondary ground
		electrode
6	5B	C47 positive	5 V spare output, provide power for on/off circuit
		electrode
7	5 V	ZD3 cathode	5 V output, voltage range is 4.75~5.25 V
8	12 V	ZD3 cathode	12 V output, voltage range is 11.0~13.0 V

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Theory of Operation	Hardware Overview

1.2.2Power Supply Board (Lithium Ion Battery)

P/N 0671 -00-0051

Trio Power Supply board specifications:

¥AC input voltage:110~240VAC+10%

¥AC input current: <1.6A

¥AC voltage frequency: 50/60+3HZ

¥Two-way output voltage: 5V/12V, normal working current is 1.3A for 5V, 1.3A for 12V.

¥Two-way output voltage has functions of short-circuit, over-current and over-voltage protection.

¥The power board has reset function.

¥The power board can manage the charging process of li-ion battery (11.1V/4.4AH). The charging time is 6.5 hours maximum.

5VDC-DC

BUCK

Voltage test

AC

AC/DC

converter

input

REC POWER

SOURCE

Power on/off control

circuit

Li-ion

Battery and

Charging

12V output

Managerent

circuit

FIGURE 1-4 Block diagram of Trio power supply board

Key Test Points

NO.

NAME

LOCATION

FUNCTION

1

Oscillator

Pin 4 of U1

Generate a oscillating frequency about 100kHZ

frequency

2

GND

CC61 negative

Primary Ground

electrode

3

D-S waveform

Q1.2

There is a waveform of about

100KHZ,107~354V between Q1.2 and the

negative electrode of C12

4

Driving

Q1.1

There is a driving waveform of about 100KHZ,

waveform

15V between Q1.1 and the negative electrode of

C12

5

Rectified

D5 anode

Secondary rectified voltage

waveform

6

VIN

C18 positive

17.6V,provide input voltage for DC-DC

electrode

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Hardware Overview	Theory of Operation

Key Test Points

NO.	NAME	LOCATION	FUNCTION
7	12V	C41 positive	12V output, voltage range is 11.0~13.0V
		electrode
8	5V	C58 positive	5V output, voltage range is 4.75~5.25V
		electrode
9	Feedback	R37 positive	There is a DC waveform of about 2.5V between
	voltage	electrode	R37

1.2.3CPU Board (Main Control Board)

P/N 0671-00-0056 or P/N 0671-00-0236

1.2.3.1Overview

Power Supply Input Voltage: +12 V±5%; +5 V±5%

The main control board uses the Coldfire series embedded microprocessor 5206e manufactured by Motorola Company. It also adopts 3.3 V low-voltage power supply to reduce the power consumption. Other main components on the main control board include: Flash, SRAM, FPGA, network controller, etc., all of which require 3.3 V power. The capacity of the Flash is 2 MB or 4 MB*, which employs two parallel-connected 512K x 16 or 1M x 16* chips and therefore uses 32-bit character width to support CPU to operate at the highest possible speed instead of accessing the DRAM for operation. The main control board has also a 4 MB memory, which is made up of two parallel-connected 1M ×16-bit chips. Because no executing program is required to be loaded, only one RTC is used. This chip uses one 225maH dry cell as the spare power supply. In addition, one 2KB E2PROM is used to store parameters. The main control board supports a resolution of 800 x 600 and provides three interfaces: a LVDS interface, a 6 bit digital interface, and a VGA interface. The monitor displays characters and waveforms, in the same color, on the screen. The support system needs 10 serial ports, and the baud rate (4800/9600/19.2 K/38.4 K/76.8 K) can be selected by software and interface buffer drives. The main control board adopts the network controller AX88796 (3.3 V, 10 MHz), which has inside 16 K high-speed buffer SRAM. The MAX5102 8-bit single-way D/A converter is used to fulfill analog output. The 5 V and 12 V regulated voltage supplies are introduced from the power board, and therefore 3.3 V and 2.5 V working supplies are respectively generated. Among them, 2.5 V is to be used for the internal verification of FPGA.

*Applies to P/N 0671-00-0056.

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Theory of Operation	Hardware Overview

RTC/E2PROM		DRAM		Flash/SRAM

Display		CPU		Network
driving
				controller
circuit

Interrupt		I/O serial		Audio
management				alarm/spare
		interface
circuit				battery

FPGA

FIGURE 1-5 Block Diagram of Trio CPU board

1.2.3.2Detailed Description

3.3 V low-voltage power supply component is used. The external power is 5 V, which is converted by the DC/DC converter into 3.3 V and 2.5 V, the latter voltage being especially used for FPGA. The main control board is connected to external devices via corresponding interfaces and input: the power supply connected to the interface board, the 9-way serial port, TFT interface, analog VGA interface, network interface, analog output and a spare serial port, etc. The BDM interface, on the board, is reserved for the purpose of software testing and downloads.

CPU

Uses Coldfire 5206e. Clock rate is 54 MHz, working voltage is 3.3 V.

FLASH

Uses two parallel-connected 512K x 16 or 1M x 16* FLASH memories. The output terminal PP1 of CPU is used to realize write-protection of FLASH. It is effective in low-level state.

*Applies to P/N 0671-00-0056.

DRAM

The Trio CPU main control board uses two parallel-connected 1M x 16 DRAM, which construct 4M address space.

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Hardware Overview	Theory of Operation

Display

The resolution is 800 x 600. Frequency is 38 MHz. It works in an appropriate SVGA mode. VRAM adopts 16-bit structure and is divided into an alphanumeric character screen and a waveform screen. To the left of the alphanumeric character screen is the corresponding waveform screen. The character screen is used to display data and flashing alarming parameters. The user can select the color of the waveform and alphanumeric characters for each parameter.

LVDS Interface

By utilizing time-share sampling, the LVDS (Low Voltage Differential Signaling) interface converts multi-channel CMOS/TTL signals into single channel, low-voltage, double-frequency differential signals. LVDS interface is generally realized by a special integrated circuit. The special LVDS chip used for display is DS90CF363A. This chip converts 18-bits of RGB data and 3 bits of LCD timing and control data (21 bits of CMOS/TTL data) into 3 LVDS data streams. Four differential signals including the 3 data streams and a phase-locked frequency are transmitted to the display screen. The working frequency of DS90CF363A is 20~65 MHz.

Reset and Parameter Storage

The CPU board uses an integrated chip CAT1161, which controls both power-on reset and parameter storage. This chip has an E2PROM with the capacity of 2K. It can be used to modify and store various nonvolatile parameters of the host. The power-on reset and WATCHDOG functions are used to realize reset function of the CPU board. When J1 is open circuit, the software can also disable WATCHDOG by using the output signal PP0 of CPU in order to realize the self test of WATCHDOG. The bus interface of this chip is I2C.

Network Controller

The network controller adopts special chip AX88796. Its working clock is 25 MHz. It also has internal 16 K high-speed buffer SRAM. The data bus of this chip is 16-bit width.

Key Test Points

NO.	NAME	FUNCTION
1	V33	Digital supply voltage: +3.3 V
2	V25	FPGA supply voltage: +2.5 V
3	V3	Lithium battery voltage: +3 V
4	CLK	CPU master clock: 54 MHz
5	PCK	FPGA and display clock: 38 MHz
6	NCK	Network chip clock: 25 MHz
7	/RST	System reset signal
8	/NINT	Network chip interrupt signal
9	DO	Signal indicating successful FPGA configuration

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Theory of Operation	Hardware Overview

1.2.4Keypad Board

P/N 0671-00-0237

CPU

(AT89C2051)

Watchdog

RAM

BUTTON

128 x 8

button

FLASH

serial communication

Main control board

button and encoder

signal input

4KX8

scan circuit

Alarm indicator

ENCODER

control circuit

Lowpass

Power

Sound

Volume

and

speaker

Effect

Amplifier

Control

Bandpass

Control

LM386

Filter

FIGURE 1-6 Keypad Block Diagram

1.2.4.1Detailed Description

This circuit has three main parts:

1.Alarm Audio Signal Circuit: The alarm audio signal circuit is made up of components including U3, U6, R8, R25, E6 (E1), R11, R12, R3 and R32. P3.3 is used to control the length of the alarm sound. R8, E1 and E6 are used to generate the rise edge and the fall edge of the sound signal. Q1 is used to make the rise edge and fall edge of the lowlevel alarm slower than those of medium/high-level alarm. D1 is used to generate the heart beat and pulse tone. If P3.2 is high, the alarm square waveform of P3.5 will pass and, as a result, control P3.2 to generate a "heart beat tone" or ÔÔrotary encoder toneÕÕ. R11, R12, R3, R32 and R18 together construct a variable voltage-dividing network which, by controlling the state of RA and RB via U3, determines the sound volume level.

2.RC Bandpass Filter/Audio Amplifier: A one-stage RC bandpass filter is used to block the low frequency component of the alarm signal (700 Hz. square wave) before it is input to the audio amplifier, LM386. This bandpass filter is made up of R13, R28, C9, C15, RA and the input resistance R in of LM386.

3.Alarm Indicator Control/Encoder and Key Scanning: The flashing of the alarm indicator in red or green is controlled by the state of microchip P1.6 and P1.7. The microprocessor scans the state of microchips P1.0~P1.2 to determine which key, or if the encoder, is pressed. The microprocessor scans the state of microchips P1.4 and P1.5 to determine if the encoder is turned and in which direction it is turned.

Key Test Points

NO.	NAME	LOCATION	FUNCTION
1	VCC	P4.4	Power input, range: 4.8~5.1V
2	GND	P4.5	Power supply and signal ground
3	RST	U1.1	CPU reset signal. At low level (<0.3V) when
			operating normally
4	Crystal oscillator	X1.1, X.2	CPU crystal oscillator. Sine wave (1.5~3.5V)
			when operating normally

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Hardware Overview	Theory of Operation

1.2.5Keypad Board

P/N 0671-00-0058

	LED	KEY
		CPU
SPEAKER		(AT89C51)
		ENCODER
	Audio Process
	Circuit	RAM
		128 X 8
		FLASH
		4K X 8
	Watchdog	Main Control
		board (Host CPU Board)

FIGURE 1-7 Keypad block diagram

1.2.5.1Detailed Description

This module detects key and encoder input signals, converts them into code then sends these coded signals to the main board. The main control board (Host CPU board) in turn sends commands back to the keyboard's control indicator and audio process circuits, which enable or disable audio and visual alarm respectively, as required.

CPU

¥Detects key and encoder input signals;

¥Controls LED status;

¥Controls Audio Process Circuit;

¥Regularly zeroes Watchdog Timer;

¥Communicates with main board.

Audio Process Circuit

Generates audio signals to drive the speaker.

Watchdog

¥Upon power-up, supplies Reset signal to CPU;

¥Provide functions of Watchdog Timer Output and voltage detection.

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Theory of Operation	Hardware Overview

Key Test Points

NO.	NAME	LOCATION	FUNCTION
1	VCC	P4.4	Power input, range: 4.8~5.2V
2	GND	P4.5	Power supply and signal ground
3	RST	U1.10	CPU reset signal. At low level(<0.3V) when
			operating normally
4	Crystal oscillator	X1.1,X.2	CPU crystal oscillator. Sine wave signal
			(1.5~3.5V) when operating normally

1.2.6Keypad Board

P/N 0671-00-0064

	LED	KEY
		CPU
SPEAKER		(PIC16F73)
		ENCODER
	Audio Process
	Circuit	RAM
		192 X 8
		FLASH
		4K X 4
	Watchdog	Main Control
		board (Host CPU Board)

FIGURE 1-8 Keypad block diagram

1.2.6.1Detailed Description

This module detects keypad and encoder input signals, converts them into code and transmits the code to the Host CPU board. The Host CPU board sends commands to the keyboard which in turn controls the indicator and audio process circuits, activating audio and visual alarms accordingly.

CPU

The Keypad Board's CPU is responsible for the following functions:

¥Detects keypad and encoder input signals

¥Controls LED status

¥Controls Audio Process Circuit

¥Regularly zeroes Watchdog Timer

¥Communicates with main board.

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Hardware Overview	Theory of Operation

Audio Process Circuit

Generates audio signals to drive the speaker.

Watchdog

¥Upon power-up, supply Reset signal to CPU

¥Provide functions of Watchdog Timer Output and voltage detection.

Key test points

NO.	NAME	LOCATION	FUNCTION
1.	5V/5B	J5 pin 1	Power input, range: 4.0~5.5V
2.	GND	J5 pin 2	Power supply and signal ground
3.	RST	J5 pin 3	CPU reset signal. At low level(<0.8V (during
			normal operation)
4.	Crystal oscillator	X1 pin 1,X1 pin 2 CPU crystal oscillator. Sine wave signal
			1.5~3.5V (during normal operation)

1.2.7TR60-C Recorder

Thermal Head

	Motor			cpld 9536	Status Detection
	driver

DC/DC

12 V > 8 V

CPU

Signal & 5 V

FIGURE 1-9 Block Diagram of TR60-C drive board

1.2.7.1Detailed Description

Thermal Head

The thermal head, the core component in the TR60-C recorder, is the PTMBL1300A thermal head, manufactured by the ALPS company.

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Theory of Operation	Hardware Overview

CPU System

The CPU system is the core of the drive board. Its task is to receive the data from the host and generate lattice messages after calculation using a specified algorithm. These messages are then sent to the thermal head for printing. The CPU system can simultaneously collect data from both the thermal head and the drive board and display data sent to the host.

Power Conversion

The recorder requires the system to provide two voltages: 12 V and 5 V. The 5 V is directly driven by the logic and analog circuit of the drive board and the thermal head. Its current is less than 150 mA. The 12 V is converted into 8 V (by the DC/DC on the board) to drive the thermal head and the motor. The current required is determined by the printing content and ranges from 0.5 A to 2 A.

Motor Drive

A small motor is used to control the paper movement at the thermal head. The processor on the drive board uses two motor drives IC LB1843 V to control and drive the motor. These two ICÕs use constant current to control and drive the motor.

Status Detection

To correctly and safely control and drive the thermal head and the motor, the drive board must use the sensor inside the thermal head to detect the following signals: the position of the chart paper, if the chart paper is installed and if the temperature of the thermal head has exceeded the limit.

Key Test Points

NO.	NAME	LOCATION	FUNCTION
1	12 V	JP3.1	Power input, range: 10~18 V
2	GND	JP3.2	Power and signal ground
3	VPP	U7.8	Power supply for heating thermal head and
			drive motor: 7.8 V~8.4 V
4	VCC	U1.14	+5 V supply: 4.75~5.25 V
5	RESET	U3.10	CPU reset signal. At high level(>2.4 V) after
			power-on

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Serial Interface Converter Board	Theory of Operation

1.3Serial Interface Converter Board

The Serial Interface Converter Board is used to convert the TTL level (5V) to RS232 level.

	P5				Serial Coverter			Serial
P1				J2	P.C.B	J1
								interface
P4(TFT_DIGTAL )
P2(CRT)	P10
P3(FOR 9000
P12 VGA)	P7(BDM
	)

P11 Host P .C .B.

P13

P17(FOR509C)

P15

P16

P6

P9

P14

P8

FIGURE 1-10 Serial Interface connection diagram

	TTL Level		RS232 Level
	Tx	Converter Board	Tx
	Rx	RS232	Rx
	G
		Converter
	5V	chip	G
			DB9 Socket
	FIGURE 1-11 Block diagram of Serial Interface Converter Board

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Theory of Operation	Parameter Circuit Descriptions

1.4Parameter Circuit Descriptions

1.4.1ECG

The main functions concerning ECG are:

¥Lead: 3-lead, 5-lead

¥Lead Method; I, II, III, avR, avL, avF, V, CAL

¥Floating Input

¥Right-Leg Drive

¥Lead-off Detection

The ECG circuit is responsible for processing the ECG signals of human body. The circuit consists of following parts:

Input Circuit: The ECG electrodes are connected into the circuit through the cable. This circuit is mainly used to protect ECG input stage and filter the signals so as to remove the outside interference.

Buffer Amplifying Circuit: Used to convert the impedance of ECG signals, so as to ensure that the ECG has a very high input impedance but only low output impedance.

Right-Leg Drive Circuit: The middle output point of the buffer amplifying circuit is reversely amplified and then fed to the RL of the 5-lead ECG to maintain the human body in a equipotential state. This method can reduce the interference and raise the commonmode rejection ratio of the circuit.

Lead-off Detection: Based on the theory that the lead-off may cause the output of the buffer amplifying circuit to change, we can use the comparator to accurately determine if the lead has fallen off. In this way, the level can also be converted into TTL level for the MPU to test.

Main Amplifying Circuit: A measurement amplifier consisting of three standard operation amplifiers.

Last Stage Processing Circuit: Used mainly to couple ECG signals, program control of the gain amplifier, filter the waveform and move the level, amplify the signal and send it to the analog-to-digital converter.

1.4.2Respiration

Respiration is measured by the thoracic impedance method. When a person is breathing, his chest moves up and down. This movement equals the impedance change between electrodes RA and LL. The monitor converts the high-frequency signals passing through RA and LL into amplitude-modulated high-frequency signals, which are then demodulated and amplified into electronic signals varying with the respiration changes and then transmitted to analog-digital converter. The RESP module is made up of a respiration circuit board and a coupling transformer. The circuit includes stages such as: oscillation, coupling, demodulation, preliminary amplification and high-gain amplification.

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1.4.3NIBP

The monitor measures non-invasive blood pressure using the oscillometric method. Detailed measurement procedures follows:

1.Inflate the cuff encircled around the upper arm until the pressure in the cuff blocks the blood flow in the artery of the upper arm.

2.Then deflate the cuff according to the requirement of the algorithm.

3.With the pressure decreasing in the cuff, the arterial blood will palpitate with the pulse, which results in pulsation in the cuff. Through the pressure sensor, connected to the bladder of the cuff, a pulsation signal synchronous with the patient's pulse will be generated.

4.After being filtered by a high-pass filter (about 1 Hz), this signal becomes the pulsating signal and is amplified. The amplified signal is then converted into a digital signal by the A/D converter.

5.After processing this digital signal, systolic pressure, diastolic pressure and mean pressure can be obtained. To avoid measurement errors, choose appropriate cuffs for patient size. The NIBP module also has an overpressure protection circuit to prevent the cuff from being inflated to a very high pressure.

The main operating modes of NIBP are:

A.Adult/Pediatric

Select according to the patient size, weight and age.

B.Manual Measurement

Manual measurement is also called single measurement. It means the monitor only performs one measurement for each time the NIBP key is pressed.

C.Interval Measurement

Interval measurement means to perform one measurement within selected time cycle. Time intervals can be set up as: 1, 2, 3, 4, 5, 10, 15 and 30 minutes, 1, 2, and 4 hours, OFF, CONT. (Continuous). If set to continuous, the monitor will perform a measurement continuously for 5 minutes then revert to an interval setting of 5 min. Continuous measurement is effective in monitoring changes in blood pressure.

1.4.4SpO2

SpO2 Plethysmograph measurement is employed to determine the oxygen saturation of hemoglobin in the arterial blood. If, for example, 97% hemoglobin molecules in the red blood cells of the arterial blood combine with oxygen, then the blood has a SpO2 oxygen saturation of 97%. The SpO2 numeric on the monitor will read 97%. The SpO2 numeric shows the percentage of hemoglobin molecules which have combined with oxygen molecules to form oxyhemoglobin. The SpO2/Pleth parameter can also provide a pulse rate signal and a plethysmograph. Arterial oxygen saturation is measured by a method called pulse oximetry. It is a continuous, non-invasive, method based on the different absorption spectra of reduced hemoglobin and oxyhemoglobin. It measures the amount of light that is transmitted through patient tissue (such as a finger or an ear).

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Theory of Operation	Parameter Circuit Descriptions

The sensor measurement wavelengths are nominally 660 nm for the Red LED and 940 nm for the Infrared LED. Maximum optical power output for LED is 4 mW. The amount of light transmitted depends on many factors, most of which are constant. However, one of these factors, arterial blood flow, varies with time because it is pulsating. By measuring the light absorption during a pulsation, it is possible to derive the oxygen saturation of the arterial blood. Detecting the pulsation gives a pleth waveform and pulse rate signal. The SpO2 value and the pleth waveform can be displayed on the main screen.

1.4.5Temperature

The temperature circuit can amplify and filter the input signal of the temperature probe and then output it into the A/D sampling circuit on the ECG/RESP board. This circuit consists of sampling switching, constant-current supply, signal amplifier, filter and probe detector. The output signal of the circuit has clamping protection to ensure that the output voltage is less than VCC. The circuit also has a self-calibrating function.

1.4.6IBP (optional)

Invasive Blood Pressure monitors arterial pressure, central venous pressure and pulmonary arterial pressure.

IBP may be measured by inserting the catheter into the appropriate blood vessel. The end of the catheter, located outside the human body, should connect directly to the pressure transducer.

Inject normal saline into the catheter. Since the liquid can transfer pressure, the pressure inside the blood vessel can be transferred to the outside pressure transducer. In this way we can obtain the waveform of the dynamic pressure inside the vessel. Systolic, diastolic and mean pressures are calculated by using an algorithm.

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