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Non-Optical Bubble Sensing Methods for Electrically Conducting Liquids

Non-Optical Bubble Sensing Methods for Electrically Conducting Liquids. Craig E. Nelson - Consultant Engineer. Goals for Bubble Sensing Devices: Detect small bubbles in a small fluid channel without immersion of sensor parts in the channel

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Non-Optical Bubble Sensing Methods for Electrically Conducting Liquids

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  1. Non-Optical Bubble Sensing Methods for Electrically Conducting Liquids Craig E. Nelson - Consultant Engineer

  2. Goals for Bubble Sensing Devices: • Detect small bubbles in a small fluid channel without immersion of sensor parts in the channel • Differentiate between a gas filled channel and a fluid filled channel • Be sensitive to rather small gas fractions passing down the small fluid channel • Desirable Features: • Small and flat • Inexpensive • Reliable

  3. Zen – No Sensor Sensor: EIS Magnetostatic Methods: Magnetostatic Bubble Sensing – Impedance Method – 1 Coil Magnetostatic Bubble Sensing – Transformer Method – 2 Coils Magnetostatic Bubble Sensing – Gradiometer Method – 3 Coils Galvanic Contact Methods: Noble Metal Electrodic Methods Permittivity ( Capacitive ) Methods: Absolute Capacitance Differential Capacitance Mass flow Methods: Mechanical Resonance of Fluid Loaded Beams Ultrasonic Methods: Pitch – Catch Mechanical Impedance

  4. Nature of the Bubbles

  5. Nature of the Bubbles

  6. Nature of the Bubbles

  7. Nature of the Bubbles

  8. Nature of the Bubbles

  9. Electrical Impedance Bubble Sensing

  10. Electrodic Bubble Sensing Methods - MEMS

  11. Zen – No Sensor Sensor - EIS Measure the liquid electrical impedance using electrode already in place for other reasons.

  12. Impedance Sensing – Single Coil

  13. Impedance Sensing - Single Coil

  14. Impedance Sensing - Single Coil Coil by itself Coil with finger tips pressed on it

  15. Transformer Sensing – 2 Coils

  16. Transformer – 2 Coils – Circuit Viewpoint

  17. Transformer – 2 Coils - Narrow Channel

  18. Flow Out Flow Out Flow Out Flow Out Flow In Flow In Flow In Flow In Transformer Bubble Sensing R1 Electrolyte fills channel – no bubbles R1 signal is attenuated for a long time R1 Small Bubble is in entry channel region R1 is momentarily less attenuated R1 Small Bubble is in center of channel R1 is attenuated for a short time R1 Gas fills the entire channel R1 is less attenuated for a long time

  19. Gradiometer Sensing – 3 Coils

  20. Gradiometer – 3 Coils – Physics Viewpoint

  21. Gradiometer – 3 Coils – Circuit Viewpoint

  22. Gradiometer - 3 Coils - Wide Channel

  23. Gradiometer – 3 Coils - Narrow Channel

  24. R2 R2 R2 R1 R1 R1 Flow Out Flow Out Flow Out Flow Out Flow In Flow In Flow In Flow In Gradiometer Bubble Sensing and Control Rule R2 R1 Electrolyte fills channel – no bubbles R1 & R2 signal is attenuated Small Bubble is in entry channel region R1 is less attenuated – R2 is not affected Small Bubble is in center of channel R1 and R2 are less attenuated for a short time Gas fills the entire channel R1 and R2 are less attenuated for a long time

  25. Other Bubble Sensing Schemes

  26. Capacitive Bubble Sensing Methods

  27. Mass Resonance Bubble Sensing - MEMS

  28. Summary and Conclusions A wide variety of by bubble detection schemes suitable for use with conductive liquids have been introduced Many of these are practical for miniature application Microprocessor based electronic readouts for these sensing schemes Are not complex or expensive

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