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Medical Instrument

Dynamic Characteristics & Biopotential. Medical Instrument. Group 3 :. 김제선 김준범 김현준 김한울 (1 등 ) 노재선. 1. 2. 3. 4. Transient response. Steady state response. Distortionless Mearsurment. Biopotential. Contents. Dynamic Characteristic. Time dependency

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Medical Instrument

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  1. Dynamic Characteristics & Biopotential Medical Instrument Group 3 : 김제선 김준범 김현준 김한울(1등) 노재선

  2. 1 2 3 4 Transient response Steady state response Distortionless Mearsurment Biopotential Medical Instrumentation Contents

  3. Medical Instrumentation Dynamic Characteristic • Time dependency • Most medical instruments must process signals that are functions of time. It is this time-varying property of medical signals that requires us to consider dynamic instrument characteristics.

  4. Medical Instrumentation Transient response CASE1 Step Response H x(t) y(t) The transfer function for a linear instrument or system expresses the relationship Between the input signal and the output signal mathematically.

  5. Medical Instrumentation Transient response System behavior Dependence of the system behavior on thevalue of the damping ratio ζ, for under-damped, critically-damped ,over-damped, and undamped cases, for zero-velocity initial condition.The behavior of the system depends on the relative values of the two fundamental parameters, the naturalrequency ω0 and the damping ratio ζ. In particular, the qualitative behavior of the system depends crucially on whether the quadratic equation for γ has one real solution, two real solutions, or two complex conjugate solutions.

  6. Medical Instrumentation Dynamic Characteristic Critical damping (ζ = 1) When ζ = 1, there is a double root γ (defined above), which is real. The system is said to be critically damped. A critically damped system converges to zero faster than any other, and without oscillating.

  7. Medical Instrumentation Transient response Over-damping (ζ > 1) When ζ > 1, the system is over-damped and there are two different real roots. An over-damped door-closer will take longer to close than a critically damped door would.

  8. Medical Instrumentation Transient response Under-damping (0 ≤ ζ < 1) Finally, when 0 ≤ ζ < 1, γ is complex, and the system is under-damped. In this situation, the system will oscillate at the natural damped frequency ωd, which is a function of the natural frequency and the damping ratio.

  9. Under-Damping Critical-Damping Over-Damping Medical Instrumentation Transient response ζ < 1 ζ = 1 ζ > 1

  10. Medical Instrumentation Dynamic Characteristic System First-order system Exponential Time constant Second-order system Natural frequency Under-damping Critical-damping Over-damping

  11. Medical Instrumentation Dynamic Characteristic x y 3차 x y 1차 2차 *인수분해에 의해서 3차는 1차, 2차로 표현 가능

  12. Medical Instrumentation Steady state response CASE2 Sinusoidal Steady State Frequency Response System

  13. Medical Instrumentation Steady state response Linear system(Principal of superposition) Linear System Linear combination Set of all x(t) is X, Basis of X = x(t) is a linear combination-dependent frequency

  14. Medical Instrumentation Steady state response Impulse response Amplitude response Convolution - LTI(Linear time invariant) Fourier Transform Phase response Frequency transfer function

  15. Medical Instrumentation Steady state response Review Euler’s law

  16. Medical Instrumentation Steady state response Example

  17. Medical Instrumentation Steady state response |H| ω ω H(jw) 각각의 주파수에 대한 출력을 알고 있으므로 입력의 합에 대한 결과 역시 알 수 있다. (Superposition)

  18. Medical Instrumentation Steady state response Input output 주파수는 같고 크기와 위상만 달라짐 [주파수에 따라 출력의 모양이 달라진다. ]

  19. Medical Instrumentation Distortionless Measurment Time delay System Instrument elements that give an output that is exactly the same as the input, Except that is delayed in time by , are defined as time-delay elements.

  20. Medical Instrumentation Distortionless Measurment transposition |H| ω Flat amplitude response A ω Linear phase response

  21. Medical Instrumentation Distortionless Measurment Example H*(jw) X(t) Y(t) “Phase = Frequency X Time”

  22. Medical Instrumentation Example of distortion(amplitude) + X(t)

  23. Medical Instrumentation Example of distortion(phase)

  24. Medical Instrumentation Example of distortion 입력의 주파수 범위가 w1에서 w2일때 무왜곡을 측정하기 위한 H(jw)? ω1 ω2 ω ω1 ω2 ω Non-causal 존재할 수 없다 빛의 속도보다 빠르면 존재

  25. Medical Instrumentation Biopotential Insulating Membrane V Insulating membrane Voltage is zero. Na+ Na+ Cl- Cl- Neutral(1%) Neutral(10%) *Half-cell potential is zero.

  26. Medical Instrumentation Biopotential Permeable Membrane V Voltage is zero. Na+ Na+ Membrane is permeable to both Na+ & Cl- Cl- Cl- Neutral(1%) Neutral(10%) *Half-cell potential is zero.

  27. Medical Instrumentation Biopotential Semi-permeable Membrane V Na+ Na+ Diffusion Repulsive Cl- Semi-permeable Membrane (Only to Na+) Cl- Neutral(1%) Neutral(10%) *Half-cell potential is zero.

  28. Medical Instrumentation Biopotential Electronic Coulomb force < Diffusion force -> Na+ permeate. V Dynamic Equilibrium Na+ Electronic Coulomb force = Diffusion force -> Na+ stop permeating Na+ Diffusion Repulsive Cl- Cl- Neutral(1%) Neutral(10%)

  29. Thank You ! Medical Instrumentaiton

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