Intensity sensors

Wilson, A., C. Punginelli, A. Gall et al. (2008). A photoactive carotenoid protein acting as light intensity sensor. Proc Natl Acad Sci 105(33) 12075-12080. 

Approach One is UV intensity set-point approach. In this approach, measurements made by the UV intensity sensor are used to control the UV reactor. The sensor is located in a position that allows it to properly respond to both changes in UV output of the lamps and UVT of the water. The sensor output and the flow rate are used to monitor the dose delivery. The set-point value for UV intensity over a range of flow rates is determined during the validation. 

Approach Three is calculated UV dose approach. Similar to Approach Two, the UV intensity sensor is placed close to the lamp. Flow rate, UVT, and UV intensity are all monitored, and the output values are used to calculate the UV dose via a validated computational algorithm developed by the UV reactor manufacturer. 

Cultivation of the cyanobacterium was performed in a 4.35 L automated helical photobioreactor (PhBR) described by Tsygankov et al. (1998a). A. variabilis PK 84 was cultivated autotrophically in the PhBR under sterile air containing 2% C02 (500 ml-min 1). Growth conditions in the PhBR were monitored by a computer system connected to built-in pH, temperature, optical density, pO, and sunlight intensity sensors. When necessary 1 or 2 polyurethane foam balls were circulated along with the culture in the PhBR to clean the inner surface of the PVC tubing. 

Smart textile and polymer fibres for structural health monitoring 335 Intensity sensors... 

In this section the final prototype is shown and some measured results are given. The prototype has been equipped with light intensity sensor enabling automatic unwinding... 

MP-suspension by automated ASTM-bulb Magnetization current by Hall-Sensor Magnetization time UV-Light intensity All Liquids (fluorescence, contamination) Process times and temperatures Function of spraying nozzles, Level of tanks Flow rates (e.g. washing, water recycling) UV-Light intensity... 

Figure Bl.19.23. Principle of simultaneous measurement of nomial and lateral (torsional) forces. The intensity difference of the upper and lower segments of the photodiode is proportional to the z-bending of the cantilever. The intensity difference between the right and left segments is proportional to the torsion, t, of the force sensor. (Taken from [110], figure 2.)...

Reverse saturable absorption is an increase in the absorption coefficient of a material that is proportional to pump intensity. This phenomenon typically involves the population of a strongly absorbing excited state and is the basis of optical limiters or sensor protection elements. A variety of electronic and molecular reorientation processes can give rise to reverse saturable absorption many materials exhibit this phenomenon, including fuUerenes, phthalocyanine compounds (qv), and organometaUic complexes. 

In contrast, various sensors are expected to respond in a predictable and controlled manner to such diverse parameters as temperature, pressure, velocity or acceleration of an object, intensity or wavelength of light or sound, rate of flow, density, viscosity, elasticity, and, perhaps most problematic, the concentration of any of millions of different chemical species. Furthermore, a sensor that responds selectively to only a single one of these parameters is often the goal, but the first attempt typically produces a device that responds to several of the other parameters as well. Interferences are the bane of sensors, which are often expected to function under, and be immune to, extremely difficult environmental conditions. 

Molecular films are of intense current concern in electronics. For instance, diacetylenes and other polymerisable monomer molecules have been incorporated into L-B films and then illuminated through a mask in such a way that the illuminated areas become polymerised, while the rest of the molecules can be dissolved away. This is one way of making a resistance for microcircuitry. L-B films have also found a major role in the making of gas-sensors (Section 11.3.3). 

Both electronic and microcomputer-based controls require information about the state of the controlled system. Sensors convert different physical variables into an electric signal that is conditioned and typically converted to a digital signal to be used in microcontrollers. The trend in the construction techniques of modern sensors is the use of silicon microstrnctures because of the good performance and the low cost of this type of device. In the energy control scope the main quantities to be measured are the temperature, pressure, flow, light intensity, humidity (RH), and the electric quantities of voltage and current. 

The idea of using propagation of intensity to measure wavefront errors is applied more direetly in the eurvature sensor. Conceptually, the irradiance is measured at two planes which are equally spaced about the telescope focus and the normalized difference in intensity obtained. 

In real curvature sensors, a vibrating membrane mirror is placed at the telescope focus, followed by a collimating lens, and a lens array. At the extremes of the membrane throw, the lens array is conjugate to the required planes. The defocus distance can be chosen by adjusting the vibration amplitude. The advantage of the collimated beam is that the beam size does not depend on the defocus distance. Optical fibers are attached to the individual lenses of the lens array, and each fiber leads to an avalanche photodiode (APD). These detectors are employed because they have zero readout noise. This wavefront sensor is practically insensitive to errors in the wavefront amplitude (by virtue of normahzing the intensity difference). 

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