Design of the sensor

One can think of the sensor as having been derived from an extractor measurement system (see Fig. 4.3), whereby the separation system was inserted between the ion source and the ion trap. 

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The MCLW sensor has been exploited by several groups for a wide range of experiments. However, both the design of the sensor and the detection scheme used in connection with the monitoring vary. This section reports on experiments using angular interrogation, absorbance detection and fluorescence detection. 

When elevated temperature is needed for its operation, an integral heater can be incorporated in the design of the sensor (Fig. 8.11). It is possible to measure either the steady-state value of the resistance or, for slower reactions, the initial slope as the function of concentration. The principal gases for which this type of sensor has found most widespread application are lower hydrocarbons. However, CO, S02, H2, NOx, and other gases have been measured. Table 8.1 lists the sensitivity of a commercial Sn02 sensor to some of these gases. 

Two main types of matrices are described for the design of the sensors a PYC based matrix [21,35] and a carbon paste based matrix [22-31, 33-52], A special design was adopted for the construction of the imprinted polymers based sensors [53]. The most reproducible design was proved to be the one based on a carbon paste matrix. The non-reproducibility of PVC-based matrices is due to non-uniformity and non-reproducibility of the repartition of the electroactive material in the matrix [2],... 

As a prerequisite for the application of biomolecular interaction studies, the sensor surface should resist NSB of biomolecules. In the following, we will demonstrate that with the proper design of the sensor surface, NSB can be effectively eliminated. 

In this chapter, an overview is presented of the main optical biosensors, the operating principle of the different devices, the design of the sensors, the technology of fabrication, the resolution, the dynamic range and detection limit of each device, the most important applications and the commercial devices on the market. Finally, an outlook of futtu"e prospects for this technology is given. 

Starting from the analytical description, we can create a first rough design of the sensor system, including the resonant frequencies for drive and detection and the sizes of the sensing element, the electrostatic comb structures, and the detecting capacitors. While this work is done, the physical properties of the technology already have to be considered. 

Both approaches represent a compromise among different requirements and also affect the degrees of freedom allowed for the design of the sensor element. The decision between the approaches depends on the requirements of the application and the production line. 

Figure 12-1. Tb shows the sensor head from the Mars rover missions of 2(K)4. The head contains a curium-244 source that emits X-rays and 5.81 MeV alpha particles. The X-rays cause fluorescence in Martian rock samples, and the alpha particles stimulate X-ray emission as well. X-ray emission stimulated by bombardment by alpha and other subatomic particles such as protons is called punicle induced X-ru emission, or I lXE. llie X-ray detector is a new room-temperature type, which in the low temperature of the Martian night (below 4U°C.) exhibits low noise and high signal-to noise ratio for excellent resolution and sensitivity. Note the concentric design of the sensor head with six (im-244 sources arranged around the central detector. The X-ray spectrum of Figure 12-14 was acquired with the sensor head.

Design of the sensor substrate used at the University of Tubingen. 

Conversely, in detectors designed for fire and gas mitigation systems presence of flame is the dangerous condition. Since the dangerous situation is reversed for these two applications, the overall design of the sensor is different especially the fail-safe characteristics. 

Most important for the construction of useful electrodes for potentiometry is the design of the sensor interface with the sample solution. This interface should be designed such that the maximum possible degree of selectivity with the interesting constituent is achieved. As a result of such efforts, the field of ion-selective electrodes (ISEs) has been established. lESs are not a priori chemical sensors. Normally, they do not fulfil the condition of being small and cheap. Nevertheless, ISEs are a very important preliminary stage on the way to highly useful chemical sensors. 

Similar to the control drive mechanism zone, there would be 300 K to 400 K regions within the Reactor Coolant and Plant Structure zone to satisfy the thermal requirements of the electronic components (primarily the cable and connectors). See Section 10.3.6.4. The temperature of the gas and surface pipes is provided to assist the design of the sensor and sensor fixture technology. 

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