Positioning sensors

The measurements are also subjec t to systematic errors ranging from sensor position, sampling methods, and instrument degradation... 

Routine temperature measurement within the Discover series is achieved by means of an IR sensor positioned beneath the cavity below the vessel. This allows accurate temperature control of the reaction even when using minimal volumes of materials (0.2 mL). The platform also accepts an optional fiber-optic temperature sensor system that addresses the need for temperature measurement where IR technology is not suitable, such as with sub-zero temperature reactions or with specialized reaction vessels. Pressure regulation is achieved by means of the IntelliVent pressure management technology. If the pressure in the vial exceeds 20 bar, the... 

The excellent detection ability for flames makes UV sensing a good method for remote fire alarm-monitoring. UV radiation after the outbreak of a fire reaches a sensor much faster than heat or smoke. Also, the distance between sensor and fire is less critical. Requirements for the sensor are high sensitivity and excellent selectivity. Radiation intensities at the sensor position may be even lower and the ambient light conditions less restricted than for combustion controlling. When used outside, solar-blindness is a must. These stringent requirements make UV fire alarm monitors expensive, and they are used in industrial environments such as production floors or warehouses rather than in private homes. 

M. Luong, J.M. Paris, D. Maquin, and J. Ragot. Observability, reliability and sensor positioning. In AICHE Spring National Meeting, pages 1-10, Houston, USA, 1995. 

The discharge temperature should always be measured with a handheld temperature probe because it provides the most accurate measurement. Thermocouple sensors positioned through transfer lines and exposed to the melt stream do not provide an acceptable measurement of the discharge temperature due to the high... 

The HIPS resin was extruded at screw speeds of 30, 60, and 90 rpm at barrel temperatures of 200, 220, and 240 °C for Zones 1, 2, and 3, respectively. The screw temperatures in Zone 3 as a function of time at the screw speeds are shown in Fig. 10.20. Because the RTDs were positioned within 1 mm of the screw root surface, they were influenced by the temperature of the material flowing in the channels. Prior to the experiment, the screw was allowed to come to a steady-state temperature without rotation. Next, the screw speed was slowly increased to a speed of 30 rpm. The time for the screw to reach a steady state after changing the screw speed to 30 rpm was found to be about 10 minutes. The temperature of the T12 and T13 locations decreased with the introduction of the resin. This was caused by the flow of cooler solid resin that conducted energy out from the screw and into the solids. At sensor positions downstream from T13, the screw temperature increased at a screw speed of 30 rpm, indicating that the resin was mostly molten in these locations. These data suggest that the solid bed extended to somewhere between 15.3 and 16.5 diameters, that is, between T13 and T14. When the screw speed was increased to 60 rpm, the T12 and T13 sensors decreased in temperature, the T14 sensor was essentially constant, and the T15, T16, and T17 sensor temperatures increased. These data are consistent with solids moving further downstream with the increase in screw speed. For this case, the end of the solids bed was likely just upstream of the T14 sensor. If the solid bed were beyond this location, the T14 temperature would have decreased. Likewise, if the solid bed ended further upstream of the T14 sensor, the temperature would have increased. When the screw speed was increased to 90 rpm, the T12, T13, and T14 temperatures decreased while the T15, T16, and T17 temperatures increased. As before, the solids bed was conveyed further downstream with the increase in screw speed. At a screw speed of 90 rpm, the solid bed likely ended between the T14 and T15 sensor positions, that is, between 16.5 and 17.8 diameters. These RTDs were influenced by the cooler solid material because they were positioned within 1 mm of the screw root surface. 

Optimal sensor positioning on a semi-indnstrial granulator. 

The experiments were carried out on a semi-industrial fluidized bed reactor, illustrated in Figure 9.6, which shows four different sensor positions (A, B, C and D). Screw fittings were used to mount the sensors in order to secure optimal sensor pickup efficiency. Sensor location A is mounted onto an orifice plate on the main supply line of liquid urea to the reactor nozzles, following Esbensen et al. [5]. The sensors B, C and D are located on the wall of reactor chambers 1, 2 and 4, respectively. 

A model for crystallization point of the urea melt sprayed into the granulator was developed based on acoustic spectra recorded from sensor position A during a trial period of 24 hours. A flow sheet of the liquid urea feed process can be seen in Figure 9.7. Sensor A is mounted onto an orifice plate inserted in the main supply pipeline of liquid urea (see Figures 9.6 and 9.7). The reference values used to calibrate the model are the crystallization temperature (called the jc point ), as determined by the pilot plant laboratory (heat table visual nucleation/crystallization detection). 

Figure 4.15 The viscosity at each sensor position of a 192-ply graphite-epoxy composite during an FDEMS sensor-controlled autoclave cure...

Radiometers for three-dimensional cure are used for simultaneous multipoint measurements, for setup and process verification of the lamp system. They can be used with UV lamps mounted on a fixed bank or a robotic arm. The collected exposure data (irradiance and total UV energy) are displayed on a computer for each sensor position. A SDCure radiometer is shown in Figure 9.7, and an example of a screen display from a 3D radiometer in Figure 9.8. 

Measurements of the oxygen concentration are made with the sensor positioned entirely in the exhaust gas from an ordinary engine. A direct current is applied between the two electrodes from a DC power source. (See Figure 2.)... 

In Chapter 3 we have seen that sensors that have very narrow band-response functions simplify the functions which relate the energy measured by the sensor to the geometry of the object, the reflectance of the object patch, and the irradiance falling onto the patch. If the response function is very narrow, it can be approximated by a delta function. In this case, the energy measured by a sensor I at sensor position X/ is given by... 

Fast response is possible with swelling-based sensing mechanisms. For example, the mapping of a chemical plume caused by a release into the air could employ such a sensor positioned on an unmanned aerial vehicle (UAV). With this vehicle traveling at 40 miles/h, subsecond response times would be required to locate and map out the released analyte. An example of this is shown in Fig. 16, which describes a thin film of poly(2,2-bistrifluoromethyl-4,5-difluoro-l,3-dioxole-co-tetrafluoroethylene), Teflon AF placed on an interferometer which in turn was placed in the nose cone of an UAV, which was positioned in a wind tunnel with the wind moving at 40 mph. Small amounts of toluene vapor were introduced into the air stream to get an idea of whether the sensor would work in such an application. The sensor responded quickly, established equilibrium in seconds, and reversibly returned to baseline after the material passed. 

Figure 19.1 Arrangements of crystal sensors in the reactor, numbers on the crystal sensors represent positions 15 sensors (Position No.l to No. 15) were used for large reactor, 13 sensors (Position No.2 to No.14) for medium reactor, 11 sensors (Position No.3 to No.13) for small reactor, 3 sensors (Position No.3, 8, and 13) for XPS analysis.

Fig. 14.30 (a) The electrode assembly, with the integrated distance-control sensor positioned within the wells of a microtiter plate, and the measuring situation, which indicates the complex NO gradient above the cell monolayer, (b) A double-barrel electrode. CE = counter electrode, RE = reference electrode.69 Reproduced by permission of Wiley-VCH Verlag GmbH Co KGaA)... 

Kontis KJ, Goldin AL 1997 Sodium channel inactivation is altered by substitution of voltage sensor positive charges. J Gen Physiol 110 403-413 (erratum 1997 Gen Physiol 110 763)... 

It is possible that convection and diffusion contribute to the lags and delays that are apparently present in the regulation of flow. The sensor position would play an important role in the flow dynamics and more elaborate studies will have to be carried out to understand fully this physiological phenomenon. 

Fig. 1. Summary of avaiiabie knowiedge on the phototaxis signaiing pathways in H. sallnarum, R. sphaeroides, and H. halophila in a Che-iike reaction scheme. H. sali-narum contains the photoreceptors SRi and SRii, which are compiexed in the membrane to their signal transducers Htri and Htrii. These transducers modulate the autokinase activity of CheA and thus modulate the phosphorylation status of CheY. Phototaxis of R. sphaeroides proceeds via its photosynthetic reaction center (RC) and electron transfer chain (ETC) via a putative redox sensor. Positive phototaxis in H. halophila occurs via a similar pathway, while its negative phototaxis is triggered by photoactive yellow protein (PYP). The signal transduction pathway for PYP is unknown one candidate is the Che system. Possible adaptation mechanisms have been omitted from this figure.

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