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Ultra-Violet Fluorescence Sensor Model 120 Continuously measures and controls the weight of ultra-light coatings applied to a variety of substrates. |
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Description The NDC Model 120 affords simple, reproducible and reliable measurement of ultra-light aqueous, solvent and thermoplastic coatings. The NDC Ultra-Violet Fluorescence (UVF) sensor operates by adding a minute amount (0.01 - .05% typical) of a fluorescent tag to the emulsion, solution or thermoplastic coating. The sensor measures the amount of the tag that is present after the coating is applied. Measurement is made in a backscatter mode from the coated side of the web. Coatings can be measured wet or dry. Typical tags have a fluorescence efficiency of 95% when exposed to ultra-violet radiation. Excitation is accomplished by a bright, efficient and safe, non-nuclear source. Data is rapidly sampled and converted to display of engineering units such as g/m2.
Theory of Operation Light emitted by a mercury lamp is filtered and collimated. The light passes through a beam splitter and lens, and then onto the product to stimulate fluorescence. Fluorescent light emitted by the product is collected by the same lens and re-collimated. This light passes through a beam splitter and filter tuned to the primary emission wavelength of the particular tag used and is focused onto the signal detector. A small portion of the ultraviolet light from the mercury lamp passes through a beam splitter and is separately detected by a reference detector to compensate for lamp intensity fluctuations. The reference and sample signals are combined, filtered to remove the effects of ambient light, and processed to produce a sample coat weight. Technical Specifications for the Ultra-Violet Fluorescence Sensor
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