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Bioimpedance Measurement Dept. of Biomedical Engineering 2003200449 YOUNHO HONG.

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Presentation on theme: "Bioimpedance Measurement Dept. of Biomedical Engineering 2003200449 YOUNHO HONG."— Presentation transcript:

1 Bioimpedance Measurement Dept. of Biomedical Engineering YOUNHO HONG

2 Impedance measure constant current source i=0 measured known Z + - impedanceresistance reactance

3 Impedance measure (Example) j Re Im iV t 1 You are given with i(t) = I sin(2 πft) You measure v(t) = V sin(2 πft+θ)

4 Impedance measure (Example) Z

5 Impedance measure

6 Z X X ? ? sin(2πft) cos(2πft) phase-sensitive Demodulation

7 Impedance measure In-phase Component

8 Impedance measure Quadrature Component

9 Impedance measure Vsin θ Vcos θ Re Im V θ (In-phase Component) (Quadrature Component) V=V I +jV Q

10 Two-electrode Method V I skin electrode equivalent circuit V Z C1 Z C2 ZbZb Inject current and then measure voltage

11 Two-electrode Method Re Im Z b cos θ b Z c1 cos θ 1 Z c2 cos θ 2 Z c1 sin θ 1 Z c2 sin θ 2 Z b sin θ b

12 Four-electrode Method V I skin E1E3E4E2 Z C1 Z C3 Z b1 Z b2 Z C4 Z C2 ZbZb

13 Three-electrode Method V I skin E1E3E2 Z C1 Z C3 Z C2 Z b1 ZbZb We can measure skin impedance using Three and Four electrode Method

14 Noise Effect

15 Spectrum Analizer A1A1 A3A3 A2A2 f1f1 ANAN f2f2 f3f3 fNfN … … X X sinw 1 t / cosw 1 t V(t) X … … sinw 2 t / cosw 2 t sinw N t / cosw N t “ DFT “

16 Bio Impedance Spectroscophy Z + - Repeat measurement for many frequencies Zb f θf

17 Thank you.


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