1. 생체계측 II Report # 송성진
Medical Instrumentation II

2. Phase–sensitive Demodulation
: 10Hz sinusoid (Tx = 0.1s)
: 50Hz sinusoid (Tc = 0.02s)
x(t)
x(t)c(t) x0 t t
-x0
0.05s
0.1s
0.05s
0.1s
Medical Instrumentation II

3. When Xo = 2, x(t) is figured by
Matlab 1.
When Xo = 2, x(t) is figured by
using matlab
Medical Instrumentation II

4. c(t) is figured by
using matlab
Medical Instrumentation II

5. x(t)c(t) is figured by
using matlab
Medical Instrumentation II

6. When c(t) is changed, figured by Matlab
Medical Instrumentation II

7. When c(t)’s frequency is 1000, x(t)c(t) is figured by
using matlab
Medical Instrumentation II

8. X LPF ? x(t)c(t)² y(t) O(t) c(t) = sin(2πx50t)
Gi ven x(t)c(t) = y(t) , find x(t) = ?
x(t)c(t)² X
LPF ?
y(t)
O(t)
c(t) = sin(2πx50t)
Because 2fc is High frequency, cut off by LPF
Medical Instrumentation II

9. Problem 9.
A conductor board is setting chest at 1mm, this is one of capacitor. Distance to chest and conductor board is changed by heart rate, A change is x(t) = sin(2πft) [mm]. At this time f is heart rate frequency. You measure x(t) that is chest’s motion by heart rate. A is 5cm² and dielectricconstant ε₀ is 8.8 x 10⁻¹² F/m, heart rate is 60bpm.
(a) represent Cx by x function. Desire for max and
min capacitance.
(b) Vi(t) = sin(2π x 10⁴t) V, C₀ is 4.4pF, V ₀(t) = ?
(c) Propose Phase-sensitive demodulator that desire
x(t) by amplifier output V ₀(t)
Medical Instrumentation II

10. Capacitive Sensor x(t) Non contact measure Chest B A Cx A B Co Vo Vi
Medical Instrumentation II

11. Constant is calculated and Vo(t) is figured by
Matlab 2.
Vi(t) X
LPF
Vo(t)
Constant is calculated and Vo(t) is figured by
using matlab
Medical Instrumentation II

12. Problem 10.
This is x₁ = x₀ + α(P1-P2), x₂ = x₀ - α(P1-P2), C₁ = εA/x₁, C₂ = εA/x₂, C₀ = εA/x₀. Ѵs = Vs <0 ̊ Phase is 1KHz.
(a) Instrument Amplifier’s input voltage is Vi.
Represent x₀, α, (P1-P2) and Ѵs.
(b) Ѵs = 1[v], x₀ = 100[μm], α = 2[μm/mmHg].
Define Instrument Amplifier gain that
output voltage phasor, V₀ sensitive
magnitude is 0.1 [v/mmHg]
(c) For desire (P1-P2) in V₀, using phase-sensitive
demodulator, Represent circuit and explain drive
principal
Medical Instrumentation II

13. Problem 10. Solution P1 P2 open Blow air C1 C2 rigid X1 X2 Diaphragm
= very flexible
When P1 = P2, C1 = C2
X1 increase / X2 decrease
P1 > P2
P1 < P2
Medical Instrumentation II

14. C1 C0 A C IA B C2 C0
Medical Instrumentation II

15. Medical Instrumentation II

16. LPF Because High frequency, cut off by LPF X y(t) sin(2πx10³t)
Medical Instrumentation II