Reflectance sensors

Reflective sensor Tape-end sensors, liquid-level sensors... 

Ahmad M., Narayanaswamy R., Fibre Optic Reflectance Sensor for the Determination of Aluminium (III) in Aqueous Environment, Anal. Chim. Acta 1994 291 255-260. 

Patskovsky, S. Meunier, M. Kabashin, A. V., Phase sensitive silicon based total internal reflection sensor, Opt. Express 2007, 15, 12523 12528... 

Laine, J.-P., Tapalian, Fl.C., Little, B.E., and Haus, FI.A., 2001, Acceleration sensor based on high-Q optical microsphere resonator and pedestal antiresonant reflecting. Sensors and... 

Ruzicka ei al. [57,58] developed some peculiar reflectance flow-through biosensors based on a sensing microzone accommodating an enzyme and an acid-base indicator (both in immobilized form) where spacial and temporal resolution of the biochemical and chemical reaction or the reversible separation of hydrogen ions was therefore impossible. The pH sensors developed by these authors (see Section 3.5.1.1) can be regarded as precedents for these reflectance sensors. The sensing approach used relies on... 

Figure 20-21 Attenuated total reflectance sensor for Cu2+. Light traveling through the waveguide is attenuated (decreased) in the cation-exchange film in the presence of Cu2. [Data from T. Shtoyko, I. Zudans. C. J. Sellskar,...

In a modern dew-point instrument, a sample is equilibrated within the headspace of a sealed chamber containing a mirror, an optical sensor, an internal fan, and an infrared thermometer (Figure A2.2.2). At equilibrium, the relative humidity of the air in the chamber is the same as the water activity of the sample. A thermoelectric (Peltier) cooler precisely controls the mirror temperature. An optical reflectance sensor detects the exact point at which condensation first appears a beam of infrared light is directed onto the mirror and reflected back to a photodetector, which detects the change in reflectance when condensation occurs on the mirror. A thermocouple attached to the mirror accurately measures the dew-point temperature. The internal fan is for air circulation to reduce vapor equilibrium time and to control the boundary layer conductance of the mirror surface (Campbell and Lewis, 1998). Additionally, an infrared thermometer measures the sample surface temperature. Both the dew-point and sample temperatures are then used to determine the water activity. The range of a commercially available dew-point meter is 0.030 to 1.000 aw, with a resolution of 0.001 aw and accuracy of 0.003 aw. Measurement time is typically less than 5 min. The performance of the instrument should be routinely verified as described in the Support Protocol. 

A typical example of semi-quantitative analysis of an organic coating on a metal surface is shown in Fig. 7.6. A matted metal sheet is industrially spray-coated with a colourless two-component coating. The task was to determine not only the coverage, something that could also be achieved by using reflectance sensors, but also whether the mixing ratio is within the specification. 

Multipass reflection sensor used for Raman scattering. 

The thin film fiber optic reflective sensor based on palladium catalyzed W03 appears to work well for detecting hydrogen, but its response time is too slow for critical applications. The sensitivity and speed of hydrogen detection can be enhanced by using the sensor film in a SPR configuration. However, in such a configuration the rapid desorption of water vapor can lead to a false indication of hydrogen whenever the sensor is exposed to a dry... 

Fig. 11 (a) Schematic drawing of the colorimetric resonant reflection sensor. White light illuminates the sensor surface by an optical fiber. A second fiber guides the reflected light to a spectrometer, (b) Schematic spectrum... 

Shtoyko, T. Zudans, I. Seliskar, C. J. Heineman, W. R. Richardson, J. N., An attenuated total reflectance sensor for copper An experiment for analytical or physical chemistry, J. Chem. Educ. 2004, 81, 1617-1619... 

Near-IR reflection sensor array for 2D mapping of H2 from catalytic hydrogen-producing materials... 

Photoelectric sensors commonly used in die protection include opposedmode sensors, fiber-optic sensors, convergent photosensors, diffuse reflective sensors, and minilight curtains. Diffuse reflective sensors and minilight curtains are typically used only for part ejection detection and are covered in a later section. 

A direct reflective photosensor has the emitter and receiver parallel to each other in a common housing (Fig. 7). Light from the emitter reflects off the target and back to the receiver to actuate the sensor. Types of direct reflective photosensors include optical proximity and diffuse reflective sensors. Direct reflective photo-... 

Diffuse reflective sensors have little trouble detecting parts with a more complex geometry, even if the parts are shiny. Complex parts scatter light in many directions and the. sen.sor can pick up extremely small amounts of this light. Even if the sensor misses an occasional part, the dies are in no danger the control will stop the press. 

To get a larger sensing area, several diffuse reflective sensors can be stacked and connected to one input on the control to make a diffu.se light curtain (see Fig. 18). 

Gas-diffusion MSFiA manifoid with integrated fiow-through opticai fiber diffuse reflectance sensor. DMPD A/,/V-dimethyi-p-phenyienediamine monohydrochioride HC hoidingcoii RC reaction coii V soienoid vaive. 

GD-MSFIA + optical fiber diffuse reflectance sensor... 

One potential approach for improved accuracy is sensor fusion, whereby readings from multiple, functionally different sensors are combined to estimate the soil properties of interest. For example, a commercial mobile sensor platform (Fig. 2.6) combined the soil pH sensing system described in reference (155) with soil apparent electrical conductivity (ECa) sensing. As ECa provides a strong indication of soil texture variations, the combination of the pH and ECa data was useful for establishing lime requirements. An NIR reflectance sensor was later added to this multi-sensor platform. ... 

Digital Optometric Device, which consists of a series of reflective sensors attached to the head of a subject. A receptive device can calculate the relative distance between each of the sensors (Bums 2006, Carpaneto 2004, Ferrario 2002, Koerhuis 2003 [9]). 

Of key importance is the sensitivity of the sensor current or voltage output, expressed as nA/ppmv or mV/ppmv of target gas, and any cross-sensitivity to nontarget gases, as mentioned above. These sensitivities are usually quantified by pre- and/or post-fieldwork laboratory calibrations where the sensor is exposed to a fixed concentration of gas. Such point calibrations assume linearity of the sensor responses to the target gases, which is generally a valid assumption see, e.g., reference In order to reduce adverse effects from possible sensitivity drift, calibrations should be performed immediately prior to or after the fieldwork. Further, the laboratory calibrations performed at room temperature ( 20-25 °Q and ambient pressure ( 1 atm) do not necessarily reflect sensor properties at the... 

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