Miniature liquid/air interface sensor

Don VerLee; Thomas Nemcek; John M. Lindberg; Jeffrey Y. Pan; Tung-Ming Huang; Joseph Trygar

doi:10.1117/12.216793

18 August 1995 Miniature liquid/air interface sensor

Don VerLee, Thomas Nemcek, John M. Lindberg, Jeffrey Y. Pan, Tung-Ming Huang, Joseph Trygar

Proceedings Volume 2622, Optical Engineering Midwest '95; (1995) https://doi.org/10.1117/12.216793
Event: Optical Engineering Midwest '95, 1995, Chicago, IL, United States

Abstract

Biomedical instrument systems often must determine whether a container or channel contains liquid or air. Many solutions to this problem have been proposed. Detectors that measure changes in capacitance, conductivity, pressure, ultrasonic coupling efficiency, and optical properties such as absorbance and index of refraction are routinely used. The ideal liquid/air interface detector would be small, inexpensive, reliable, immune to external influences, and chemically and physically compatible with the fluids being interrogated. We present a small liquid detector that uses failure of total internal reflection to indicate the transitions between air and liquid in a fluid conduit or container. The detector is manufactured with the same materials as the channels and chambers themselves, and as such is completely inert to the assay fluids it contacts. It is also relatively immune to external interference such as electromagnetic fields, ambient light, and physical variations in the fluids. It is tolerant of manufacturing variations, and would be inexpensive if manufactured even in moderate quantities. A few critical performance variables are analyzed and results from early testing of the sensor are discussed.

Citation Download Citation

Don VerLee, Thomas Nemcek, John M. Lindberg, Jeffrey Y. Pan, Tung-Ming Huang, and Joseph Trygar "Miniature liquid/air interface sensor", Proc. SPIE 2622, Optical Engineering Midwest '95, (18 August 1995); https://doi.org/10.1117/12.216793

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