Fluoroptictm Velocity Sensor

Michael H Ikeda; Mei H Sun; Stephen R Phillips

doi:10.1117/12.945230

8 April 1988 Fluoroptictm Velocity Sensor

Michael H Ikeda, Mei H Sun, Stephen R Phillips

Proceedings Volume 0904, Microsensors and Catheter-Based Imaging Technology; (1988) https://doi.org/10.1117/12.945230
Event: 1988 Los Angeles Symposium: O-E/LASE '88, 1988, Los Angeles, CA, United States

Abstract

A fiber optic velocity sensor was developed based on optical heating of a fluoropticTm temperature sensor. Infrared radiation is pumped into the temperature sensor, thereby raising its equilibrium temperature. When the heated sensor is placed in thermal contact with a flowing fluid, heat is carried away by the fluid, lowering the sensor temperature. This energy loss is correlated to local flow rate or velocity. This approach to flow measurement is the optical analogy of the hot wire/hot film anemometer. The velocity probe consists of a single multimode optical fiber with temperature sensitive phosphor and heat absorber material attached to the tip. A short pulse of blue excitation light pumped into the fiber causes the phosphor to fluoresce. After the exitation has terminated, the exponential decay time of the fluorescent radiation intensity is measured and correlated with temperature. The optical heating energy is provided by a continuous wave (CW) infrared laser diode. The infrared light pumped into the fiber impinges on the absorber material, heating the phosphor sensor. The temperature measurement is utilized in a feedback control loop to modulate the CW laser diode. The sensor temperature is maintained constant utilizing pulse width modulation of laser diode drive current. The resulting duty cycle (laser input energy) is correlated to fluid flow velocity. Data are presented for volumetric flow rates in the range of 0 to 10 liters/minute in a 1.9 cm diameter tube showing very promising results.

Citation Download Citation

Michael H Ikeda, Mei H Sun, and Stephen R Phillips "Fluoroptictm Velocity Sensor", Proc. SPIE 0904, Microsensors and Catheter-Based Imaging Technology, (8 April 1988); https://doi.org/10.1117/12.945230

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