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Phasors and Capacitors

Phasors and Capacitors. Spin My World Right Round. LPF Application: Gastric Electrical Activity. 60-70 million people suffer from GI disorder Electrically active organ. http://www.virtualmedicalcentre.com/anatomy/gastrointestinal-system/7. Electrogastrogram and Slow Wave mapping.

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Phasors and Capacitors

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  1. Phasors and Capacitors Spin My World Right Round

  2. LPF Application: Gastric Electrical Activity • 60-70 million people suffer from GI disorder • Electrically active organ http://www.virtualmedicalcentre.com/anatomy/gastrointestinal-system/7

  3. Electrogastrogram and Slow Wave mapping Flexible Electrode Array (256 electrodes) Recording the EGG (6 electrodes) Typical gastric slow wave recording (freq ~ 0.05 Hz) Slow wave map tracks spread of electrical activity

  4. Noise corrupting the recording Signal of interest Noise (oscillations so fast you can’t see the individual waves) What the electrode records (ruh-roh!)

  5. Graphical Representation of Cosines w Blue = Vin(t) Red = VC(t) Green = VR(t)

  6. Describing a cosine wave with phasors 4.33 2.5 0 5

  7. How about a sine wave?

  8. Phasors! -sinwt coswt -coswt sinwt Rotates in time But we just read off the magnitude and phaseinformation

  9. Red vs. blue: What’s different? 1. Magnitude 2. Phase

  10. All shapes and sizes… Typical ones you’ll find in the lab Some big and some small…

  11. These are capacitors too! Cell membrane Icky cells (bacteria)

  12. And so is this! PC board Red = top layer Green = bottom layer

  13. Implementing a low pass filter (LPF) Strongly attenuated 60Hz Barely attenuated 0.05Hz

  14. 60 Hz signal zoomed in f

  15. Raw vs. Filtered Signal

  16. Low Pass Filter Example: Vout and Vin

  17. Vout, Vc, and VR

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