Sensors computerized

For polyethylene coatings on paper, the control of surface quality can be investigated by a multiple-sensor computerized control system [66]. The thickness of very thin coatings must be determined by radiometric recording of neutron absorption [67]. 

Monitoring by Electromechanical Instrumentation. According to basic engineering principles, no process can be conducted safely and effectively unless instantaneous information is available about its conditions. AH sterilizers are equipped with gauges, sensors (qv), and timers for the measurement of the various critical process parameters. More and more sterilizers are equipped with computerized control to eliminate the possibiUty of human error. However, electromechanical instmmentation is subject to random breakdowns or drifts from caUbrated settings and requires regular preventive maintenance procedures. 

Maintenance "indicators" are available to help facility staff determine when routine maintenance is required. For example, air filters are often neglected (sometimes due to reasons such as difficult access) and fail to receive maintenance at proper intervals. Installation of an inexpensive manometer, an instrument used to monitor the pressure loss across a filter bank, can give an immediate indication of filter condition without having to open the unit to visually observe the actual filter. Computerized systems are available that can prompt staff to carry out maintenance activities at the proper intervals. Some of these programs can be connected to building equipment so that a signal is transmitted to staff if a piece of equipment malfunctions. Individual areas can be monitored for temperature, air movement, humidity, and carbon dioxide, and new sensors are constantly entering the market. 

Qualification tests shall be carried out in order to check the transmission of one-bit binary information sent by sensors and safeties to the computerized control system or programmable logic controller. 

Tests aim to check the alarm conditions and safeties available on the computerized equipment, even those with low activation probability. Each alarm or safety checked is activated between one and three times, possibly substituting some sensor with an appropriate calibrator simulator. 

Figure 3 shows a TWC system and a typical performance of the TWC. The three components are highly purified over the catalyst around the stoichiometric point. The oxidizing and reducing components have almost the same chemical equivalent in the narrow shadowed region, and CO, HC and NOx are converted into H20, C02 and N2 (Fig. 3b). The atmosphere of the TWC is automatically controlled around the stoichiometric point by the TWC system. The flow rate of air is monitored and the fuel injection is controlled by a computerized system to obtain a suitable A/F ratio (Fig. 3c). The signal from oxygen sensor is used as a feedback for the fuel and air injection control loop. Therefore, the exhaust gases are fluctuating streams between oxidizing and reducing periodically and alternatively.

The acceleration is a direct measure to the dynamic factors. However, there are few reports, if not to say none, about that for meso-scale structures. In a recent attempt, Meng et al. (2009) made use of the multiple sensors of an X-ray computerized tomography (CT) to measure the cluster accelerations. Instead of the conventional use of CT for cross-sectionally scanning the solids distribution, they erected the X-ray fan-beam and the sensors to follow the vertical movement of clusters... 

Information from these sensors and data from conventional sensors that monitor are gathered and sent to a computerized decision making system. This decision-maker includes an expert system and a mathematical model of the process. The system then makes any changes necessary in the production process to ensure the material s structure is forming properly. These might include changing temperature or pressure profiles, or altering other variables that will lead to a defect-free fabricated product. 

CARE Computerized Airborne Release Evaluation Environmental Systems Corporation Ron Webb 200 Tech Center Dr. Knoxville. TN 37912 (615) 688-7900 Uses mathematical models to assess gas cloud movements. Uses gas detectors and weather sensors to alert user of release, and provides plume dispersion, effects, and response information. 

Overall, the prospects for development of practical electronic noses based on AW sensor arrays and computerized pattern recognition are very good. A current design for such an instrument consists of an array of four 250-MHz SAW resonators along with RF electronics, frequency counters, interface circuitry, and neural-network pattern-recognition computer. The complete instrument occupies a volume of 500 cm (i.e., 11.4 X 11.4 X 3.8 cm) and uses less than 2 W of power. Improvements in the near future should allow the volume to shrink to less than 160 cm with a power consumption of about 0.7 W. While this is still a rather large nose, further improvements in size and performance are quite likely. Thus, the quest for a small instrument having a volume of a few cubic centimeters and the ability to detect and identify vapors at the part-per-million concentration level (i.e., a truly versatile electronic nose) appears to be achievable. 

The system of Wall et al. (17) consisted of a large Norlake walk-in temperature and humidity-controlled chamber containing fluorescent lamps and a large number of individual sensors to monitor the chambers 160 shelves. This system was computerized to measure all-important parameters including illumination levels, automatically, continuously. 

In the era of single-loop control systems in chemical processing plants, there was little infrastructure for monitoring multivariable processes by using multivariate statistical techniques. A limited number of process and quality variables were measured in most plants, and use of univariate SPM tools for monitoring critical process and quality variables seemed appropriate. The installation of computerized data acquisition and storage systems, the availability of inexpensive sensors for typical process variables such as temperature, flow rate, and pressure, and the development of advanced chemical analysis systems that can provide reliable information on quality variables at high frequencies increased the number of variables measured at... 

An even more precise version of this sensor type was specially designed for in vivo application and consists of a 25-gauge hypodermic needle with an ion-permeable side window and 75-pm fibers. It had a response time of 3 s. Together with computerized signal processing and three-point calibration, a precision of 0.001 pH unit in the pH range 7.0-7.4 was achieved. The sensor has been used in studies of the transmural pH gradient in myocardial ischemia [53] and for continuous measurement of intravascular pH [54]. 

Further development of the pH probe for practical use was continued by Markle and colleagues [21]. They designed the fiber optic probe in the form of a 25-gauge (0.5 mm OD) hypodermic needle, with an ion-permeable side window, using 75-p.m-diameter plastic optical fibers. The sensor had a 90% response time of 30 s. With improved instrumentation and computerized signal processing and with a three-point calibration, the range was extended to 3 pH units, and a precision of 0.001 pH units was achieved. 

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