Optical Relative Humidity Sensor Research Articles

Fiber optic relative humidity sensor based on the tilted fiber Bragg grating coated with graphene oxide

A fiber optic relative humidity (RH) sensor based on the tilted fiber Bragg grating (TFBG) coated with graphene oxide (GO) film was presented. Amplitudes of the cladding mode resonances of the TFGB varies with the water sorption and desorption processes of the GO film, because of the strong interactions between the excited backward propagating cladding modes and the GO film. By detecting the transmission intensity changes of the cladding mode resonant dips at the wavelength of 1557 nm, the maximum sensitivity of 0.129 dB/%RH with a linear correlation coefficient of 99% under the RH range of 10–80% was obtained. The Bragg mode of TFBG can be used as power or wavelength references, since it is inherently insensitive to RH changes. In addition, the proposed humidity sensor shows a good performance in repeatability and stability.

Optical relative humidity sensor with high sensitivity based on a polyimide-coated symmetrical metal-cladding waveguide.

An optical structure for relative humidity (RH) sensing based on a polyimide-coated symmetrical metal-cladding waveguide is proposed. The diffusion of water molecules into the polyimide film leads to a combined change of thickness and refractive index. Due to the high sensitivity of ultrahigh-order modes, the interaction between water molecules and polyimide will give rise to a dramatic variation in the reflected light intensity. Our optical RH sensor exhibits a good linearity and a high RH resolution of approximately 0.16% for RH values ranging from 36% to 76%. In addition, it provides a short response time, a favorable stability over a long period, and a small degree of hysteresis.

Optical relative humidity sensor based on a hollow core-photonic bandgap fiber

We propose a novel relative humidity (RH) sensor based on a hollow core-photonic bandgap fiber (HC-PBF) using a wavelength scan and a reference technique in this paper. The wavelength scan of water vapor absorption peak around 1368.59 nm is realized by injecting sawtooth modulated current to a DFB laser diode. The humidity level is determined by the voltage difference (ΔV) between the reference signal and absorption signal at the peak of water vapor absorption. The reference signal is used not only as a zero absorption baseline but also to reduce the influence of intensity noise from DFB laser source. We have experimentally implemented the wavelength scanning modulation scheme with a HC-PBF sensing head of 5 cm and a small gap between SMF and HC-PBF to allow air diffusion into air holes of HC-PBF. High humidity sensitivity of 3.02 mV/1% RH over the range from 0 to 90% RH is achieved without the use of any coating material for humidity sensing.

High dynamic range fiber optic relative humidity sensor

We present a fiber optic relative humidity sensor. The sensor was fabricated by coating a thin polyvinyl alcohol/CoCl 2 film on a 200-μm core plastic-cladding fiber; the film was deposited after removing the cladding of the fiber. It was found that bending the fiber leads to drastic changes in the response behavior. The sensor was compared against a commercially available relative humidity sensor and was found to be sensitive to relative humidity ranging from 3 to 90%. The sensor response is usually very fast, but varies at different humidity levels and has a good dynamical range. The sensor response is repeatable and fully reversible, and should be useful for monitoring relative humidity in harsh industrial environments.

Evaluation of Nafion–Crystal Violet films for the construction of an optical relative humidity sensor

Download options Please wait... Article information DOI https://doi.org/10.1039/A905264J Article type Paper Download Citation Analyst, 1999,124, 1623-1627 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Evaluation of Nafion–Crystal Violet films for the construction of an optical relative humidity sensor I. M. Raimundo Jr. and R. Narayanaswamy, Analyst, 1999, 124, 1623 DOI: 10.1039/A905264J To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Ivo M. Raimundo Jr. R. Narayanaswamy

Effect of humidity on the fluorescence properties of a medium- sensitive fluorophore in a hydrophilic polymer film

The fluorescence characteristics of 5-dimethylaminonaphthalene-1-sulphonic acid (DNSA) were examined in a hydroxypropylcellulose (HPC) film as a function of the surrounding relative humidity (RH). When the RH changed from 0% to 87%, a red-wavelength shift in the maximum fluorescence wavelength (λmax) from 435 to 465 nm was observed, accompanying a decrease in the maximum fluorescence intensity. A plot of λmax against the water concentration in the film at different RHs was approximately linear, indicating that the λmax of DNSA can be used as a measure of the water vapour uptake in the film. Since the relative intensity at a fixed wavelength of 418 nm showed a monotonic decrease with increasing RH, the DNSA—HPC film can be applied as an optical RH sensor. Kinetic studies clarified that the response of the relative intensity to abrupt RH changes followed a first-order rate law. A small reduction in the fluorescence intensity of DNSA was found after repeated humidification and desiccation of the film, suggesting increasing association of the dye in the film during these processes.

Development of an optical relative humidity sensor. Cobalt chloride optical absorbency sensor study

De la cellulose impregnee avec du chlorure de cobalt a ete utilisee pour la mesure quantitative de l'humidite relative. La diminution de la teneur en chlorure de cobalt dans la matrice fait chuter les effets d'hysteresis et le domaine effectif d'analyse, par contre l'acetylation de la cellulose accroit ce domaine