for measurement of ecg

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。