Application of flexible sapphire fibers as temperature control sensors in high-temperature multizone furnaces

Christian Stenzel; Georgios Vavoulidis; Hartmut Sauermann; Hagen Schultz

doi:10.1117/12.397884

31 August 2000 Application of flexible sapphire fibers as temperature control sensors in high-temperature multizone furnaces

Christian Stenzel, Georgios Vavoulidis, Hartmut Sauermann, Hagen Schultz

Author Affiliations +

Proceedings Volume 4074, Applications of Optical Fiber Sensors; (2000) https://doi.org/10.1117/12.397884
Event: Symposium on Applied Photonics, 2000, Glasgow, United Kingdom

Abstract

Optical Fiber Thermometry (OFT) using single-crystalline, flexible sapphire fibers combines the benefits of a pyrometric temperature measurement concerning accuracy and resolution with a high local sensitivity and low invasiveness as given for a thermocouple. In the first part of the work flexible OFT sensors have been manufactured from bare fibers and characterized with respect to optical properties like the effective acceptance angle and parasitic light entering the fiber sideways and to the minimum bending radius. The tests have yielded that the optical quality of the fibers with a diameter of 325 micrometers , 150 micrometers , or 100 micrometers is sufficient for the application as control sensors in a high-temperature furnace. However, bending of these fibers at temperatures above 1000 degree(s)C has turned out to be very critical. Finally, an active temperature control loop for a multi-zone furnace using rigid and flexible fibers as sensing elements for a temperature of 1500 degree(s)C has been developed. The control algorithm which takes the thermal coupling between neighboring zones into account could establish a short-term stability of (Delta) T equals 0.015 degree(s)C over 25 min for all four zones. This achieved control stability is improved by one order of magnitude compared to a thermocouple based control system.

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Christian Stenzel, Georgios Vavoulidis, Hartmut Sauermann, and Hagen Schultz "Application of flexible sapphire fibers as temperature control sensors in high-temperature multizone furnaces", Proc. SPIE 4074, Applications of Optical Fiber Sensors, (31 August 2000); https://doi.org/10.1117/12.397884

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