for measurement of ecg
DESCRIPTION
For Measurement of ECG. m5151117 Yumiko Kimezawa. Outline. Our Architecture Important Things in Measurement of ECG Signal Book Knowledge Question Requirements for Measurement of ECG Future Work. Our Architecture. Processing results are sent through the Ethernet. Sensor. A/D - PowerPoint PPT PresentationTRANSCRIPT
For Measurement of ECG
m5151117Yumiko Kimezawa
October 14, 2011 RPS 1
Outline
• Our Architecture• Important Things in Measurement of ECG
Signal• Book Knowledge• Question• Requirements for Measurement of ECG• Future Work
October 14, 2011 RPS 2
Our Architecture
October 14, 2011 RPS 3
A/Dconverter Filter RAM Processing Results
From patient
SensorProcessing results are sent through the Ethernet
Important Things in Measurement of ECG Signal
• Clinically-important frequency component of ECG signal- 0 ~ 250Hz
October 14, 2011 RPS 4
• Change in voltage in chest wall- Less than 3mV (very weak)
• Measurement in environments with much noise
Change in voltage inside this range must be faithfully reproduced
Voltage gain of high signal-to-noise ratio (250 to 1000 times) must be gained• Signal-to-noise ratio: The ratio of signal power to the noise power
Book Knowledge
October 14, 2011 RPS 5
Impedance converter
Lead network
Head amplifier
Micro computerADCMain
amplifier
Isolation circuit
Output equipment
Lead Code
Power Circuit
•An example of block diagram illustrating cardiography equipment
Book Knowledge
October 14, 2011 RPS 6
Impedance converter
Lead network
Head amplifier
Micro computerADCMain
amplifier
Isolation circuit
Output equipment
Lead Code
Power Circuit
•An example of block diagram illustrating cardiography equipment
•This circuit prevents body’s impedance from being lower than input circuit’s impedance
Book Knowledge
October 14, 2011 RPS 7
Impedance converter
Lead network
Head amplifier
Micro computerADCMain
amplifier
Isolation circuit
Output equipment
Lead Code
Power Circuit
•An example of block diagram illustrating cardiography equipment
•Constitution of 12-lead from the combination of sensors•A~J : Sensors•Example
- Ⅰ: Output between A and E- aVR: Output between A and F
Book Knowledge
October 14, 2011 RPS 8
Impedance converter
Lead network
Head amplifier
Micro computerADCMain
amplifier
Isolation circuit
Output equipment
Lead Code
Power Circuit
•An example of block diagram illustrating cardiography equipment•ECG signal is very weak
•The signal must not be amplified suddenly
•Differential amplifier is used as head amplifier
An amplifier is needed
The signal is amplified in stages
• Noises are reduced• signal-to-noise ratio is
improved
Book Knowledge
October 14, 2011 RPS 9
Impedance converter
Lead network
Head amplifier
Micro computerADCMain
amplifier
Isolation circuit
Output equipment
Lead Code
Power Circuit
•An example of block diagram illustrating cardiography equipment
•For securing of security, impedance converter, lead network and head amplifier have to be isolated from main amplifier, power circuit and A/D converter
Question•A/D converter (AD9254) is included in HSMC- Pipelined switched capacitor ADC- Sampling frequency: 150MHz- Resolution: 14-bit- Power: 430mW
October 14, 2011 RPS 10
HSMC
Performance is overmuch•Clinically-important frequency component of ECG signal is from 0 to 250Hz
500Hz is enough for sampling frequency
•Using a lot of electricity•Conversion process is complex•Using A/D converter in HSMC is of questionable value
Requirements for Measurement of ECG
• An amplifier is needed• Securing of security also have to be considered
October 14, 2011 RPS 11
Future Work
• Studying cardiography equipment using digital filtering techniques
October 14, 2011 RPS 12
October 14, 2011 RPS 13
心電計の回路を表すブロック図の例
October 14, 2011 RPS 14
インピーダンス変換器
誘導ネットワーク
前置増幅器
マイクロコンピュータ
AD変換器主増幅器
アイソレーション回路
出力装置
誘導コード 電源回路
標準１２誘導を作るための誘導ネットワークの原理
October 14, 2011 RPS 15
A
B C D
E
F
G
HI
J
A~Jの各点の出力を組み合わせる。例えば、第Ⅰ誘導は AとE、 aVRは AとFを組み合わせたものとなる。