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8 December 2004 Humidity sensing using plastic optical fibers
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Proceedings Volume 5590, Sensors for Harsh Environments; (2004)
Event: Optics East, 2004, Philadelphia, Pennsylvania, United States
A low cost, low complexity fiber optic humidity sensor is very desirable because of the various advantages fiber optic sensors have over conventional electrical sensors. In this paper a simple, low cost plastic optical fiber (POF) sensor based on cobalt chloride (CoCl2) and gelatin coating on the curved sensing point with a humidity sensing range from 60% to 95%RH is presented. An investigation into the effect of bending radii of the fiber at the sensing point as well as fiber core diameter on sensitivity of the humidity sensor is conducted to find the best way to improve sensing performance. The sensing mechanism of the POF humidity sensor is the attenuation of the evanescent wave at the bent portion of the fiber by absorption due to CoCl2. The sensor has a sensing range from 60%RH to 95%RH. The hysteresis error is negligible and a resolution of 0.01%RH is achieved. The repeatability error can be as low as 1.1% for the whole sensing range. Investigation of the effect of fiber diameter shows that the sensitivity of the sensor improves with larger fiber diameters. The sensitivity of the sensor increases when the sensing portion of the fiber is bent to a small radius.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Chia Meng Tay, Khay Ming Tan, Swee Chuan Tjin, Chi Chiu Chan, and Harianto Rahardjo "Humidity sensing using plastic optical fibers", Proc. SPIE 5590, Sensors for Harsh Environments, (8 December 2004);

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