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Applied Electronic Circuit

Applied Electronic Circuit. #7 . 2007102832 김명준. Instrumentation Amplifier : IA. High Input Impedance Low Output Impedance Accurate and Stable Gain (1 ~ 1000) High CMRR . Instrumentation Amplifier : IA. 이득가변. For CMRR Tuning. Instrumentation Amplifier : IA. Differential Mode Input –

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Applied Electronic Circuit

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  1. Applied Electronic Circuit #7 2007102832 김명준

  2. Instrumentation Amplifier : IA High Input Impedance Low Output Impedance Accurate and Stable Gain (1 ~ 1000) High CMRR

  3. Instrumentation Amplifier : IA 이득가변 For CMRR Tuning

  4. Instrumentation Amplifier : IA Differential Mode Input – Differential Mode Output Amplifier One Chip Instrumentation Amplifier AD620 oretc

  5. Dual OP AMP Instrumentation Amplifier 단점 신호가 소자 통과 시 time delay 발생! 이 에 비해 time delay가 크다. → phase distortion 발생 Gain 조절 쉽지 않다

  6. Ground loop Stray capacitor 실제로는 도선에 연결된 Capacitor가 아닌 매질을 통해 연결된 가상의 Capacitor 도선 자체 저항

  7. Ground loop , but is possible. CMRR 감소의 원인 R 감소 방법 : lead wire를 짧고 굵은 선으로!

  8. Shield Cable 도자기 절연체 도체 cable coaxial cable 절연체 Triaxial cable

  9. Shield 220V 60Hz 도체 (등전위면) Shield(차폐) : 적절한전압 유지 Chassis Grounded Shield(접지 차폐)

  10. Shield 220V 60Hz Shield 가능 + - IA Shield 불가능 Ground Shield 오히려 더 나빠진다→ 원치 않는 DM current 더 생겨 전원 전압에 의한 interference 제거 Leakage Current increased

  11. Shield Cable에 흐르는 전압과 같은 전압을 Shield에 Drive - + + - IA - + Active Shield (Driven Shield)

  12. Shield Active Shield& Ground Shield - + 전체가 Ground Shield

  13. Transducer Bridge Amplifier Resistive Sensor Temperature ; Thermister, RTD Light ; Photoresistor Strain ; Straingage Pressure ; piezo resistive sensor 물리량의 변화 -> 저항의 변화 -> 전압의 변화

  14. Bridge Circuit 일 때, → Balanced AC 사용할 수 있음 Capacitive sensor Inductive Sensor

  15. Conduction in Metal (Conductor) e- e- e- e- mobility T↑, + + + + e- e- e- e- + + + + n; 자유전자의 부피밀도 e- e- e- e- 전류밀도 + + + + = conductivity

  16. Conduction in Metal (Conductor) T[s] 동안 L[m] 이동한다면, N개의 Free electron A L

  17. Conduction in Metal (Conductor) 온도계수(Temp wett.)

  18. Conduction in Metal (Conductor) Ex. Pt RTD

  19. Conduction in Metal (Conductor) Ex. Pt RTD (xA)

  20. Conduction in Metal (Conductor) Ex. Pt RTD To prevent self heating 최종적으로 0.1V/℃의출력을 얻기 위하여 margin T: 0~100℃ → : 0~10V Ω

  21. Conduction in Metal (Conductor) Ex. Pt RTD 근사식이 아닌 식을 사용하면, 근사식인 경우에 비해 약 0.26℃ 차이 발생

  22. Bridge Balancing Bridge Arm에 흐르는 전류를 제어 → 민감도 조절 1% 저항, 5% 전원 사용 0-2V Balancing (영점 조정) 2mA ⓐ 14V 1mA 1mA 14-16V (xA) 전원 : V 변동

  23. Bridge Balancing To be safe, 라 가정 280 변화 ⓐ점의 전압=14V To be safe, 전압=0~2V Choose 에 흐르는 전류= 2mA

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