1. 생체계측 II Report # 송성진
Medical Instrumentation II

2. <Electric Circuit> <Fluid Mechanics>
Multi physics.
ref.
<Electric Circuit>
V o l t a g e
C u r r e n t
C h a r g e
<Fluid Mechanics>
P r e s s u r e
F l o w
V o l u m e
ρ is density
L is length
η is viscosity
C is compliance
ρ is resistivity
Medical Instrumentation II

3. We must measure pressure, Pi !
Catheter Model.
We must measure pressure, Pi !
Diaphragm +
Strain gage
Pi -> Vi -
Cable
Blood vessel
Po -> Vo
Sensor
Medical Instrumentation II

4. Equivalent Circuit Model.1) 2)
Medical Instrumentation II

5. 3) Second order Ordinary Differential Equation(ODE)
4) Laplace equivalent transform
Medical Instrumentation II

6. (or undamped Frequency)
Damping Ratio
Natural Frequency
(or undamped Frequency)
Medical Instrumentation II

7. Frequency transfer function
Medical Instrumentation II

8. Medical Instrumentation II

9. We know that Wn is 1/root(LcCd)
1/2ζ
∞ → 0 Wn ω
We know that Wn is 1/root(LcCd)
almost 80Hz ~ 90Hz
Medical Instrumentation II

10. 1. If ζ = 0.5 , Flat (response) ІHІ 1/2ζ = 1 Wn ω Critical damping
But, Wn is increasing, not flat
So ІHІ is decreasing
Medical Instrumentation II

11. 2. If ζ = 1 , ІHІ 1 1/2ζ = 0.5 Wn ω Over damped
It is that high frequency decreasing
Medical Instrumentation II

12. so that amplified same magnitude.
Ex)
Іvi(ј ω)І
Wn is going to be more 30Hz
so that amplified same magnitude. ω
30Hz
If Іvi(ј ω)І
Medical Instrumentation II

13. If ζ = 0.25 , Ex) ІHІ 1/2ζ = 2 1 ω Wn Under damped
Medical Instrumentation II

14. We must regulate phase & magnitude response appropriate
Phaser transfer graph
<H Wn
→ ∞ ω
We must regulate phase & magnitude response appropriate
-π/2 -π
ζ increasing -> G -> B -> R
Medical Instrumentation II

15. Question) Why change D by jω?
1. D operation
General RLC Circuit
d/dt Δ= D (operater)
Operational
transfer function
Medical Instrumentation II

16. 2. Fourier transform
Medical Instrumentation II

17. Medical Instrumentation II