Sensors, types

Sensors form a very broad-based, multihilHon doUar business. Detailed information and predictions of the growth in the many sensor subftelds can be found in the Hterature (39). Eor example, the relatively narrow area of acceleration and vibrations sensors was a 600 million business in 1995 and projected to become a 1 biUion business by the end of the twentieth century. New appHcations, often driven by regulatory and safety concerns, mean projected growth of just about every sensor type. 

Nowadays all over the world considerable attention is focused on development of chemical sensors for the detection of various organic compounds in solutions and gas phase. One of the possible sensor types for organic compounds in solutions detection is optochemotronic sensor - device of liquid-phase optoelectronics that utilize effect of electrogenerated chemiluminescence. In order to enhance selectivity and broaden the range of detected substances the modification of working electrode of optochemotronic cell with organic films is used. Composition and deposition technique of modifying films considerably influence on electrochemical and physical processes in the sensor. 

Sensors that operate on the basis of interactive chemical surfaces are chosen for discussion here because they are likely candidates for the detection of chemical agents. However, many other sensor types are possible. 

Lambeck P.V., Hoekstra H.J.W.M., VanLith J., Van Elzakker G., Two novel integrated optical sensor types for measuring chemical concentrations, based on chemically induced changes of modal field profiles, J. Nonlinear Opt Phys. Mat 2004 13 (2) 209-217. 

Many advantages arise from a heterogeneous array including the miniaturization of the array, the high density of different sensor types, the presence of many replicates of each sensor type, shorter detection times due to the small sensor sizes, low materials cost, and the ease of preparation. 

Figure 5. Schematic depiction of a self-encoded bead array. A mixture of three sensor types fills the fiber tip wells randomly. The sensors are identified by their characteristic responses to a test vapor pulse. Reprinted with permission from ref. 9b. Copyright 1999 American Chemical Society.

Figure 6. Response profiles from three different sensor types, (a) Concatenated Responses of each of the individual sensor types (decoded array), (b) The collective response (undecoded array). Reprinted with permission from ref. 11. Copyright 2003 American Chemical Society.

Routine calibration of an NO sensor is essential in order to ensure accurate experimental results. One of three calibration techniques is generally used, depending on the sensor type, and will be described in the following section. Each of these methods has already been the subject of several reviews [23, 72-74] and will therefore only be summarized here. NO sensors are typically sensitive to temperature. Therefore, calibration is usually best performed at the temperature at which the measurements will be made. 

The history of ion-selective electrodes (ISEs) [1] starts from the discovery of the pH response of thin film glass membranes by Cremer in 1906, thus making ISEs the oldest class of chemical sensors. They still are superior over other sensor types in a variety... 

Sensor type Probe ssDNA density Electrolyte Target cDNA Sensor signal Hybridization time RE Ref. 

Carbon Monoxide Evolution. Determination of the carbon monoxide evolved during combustion of polymer samples in NBS Chamber experiments was carried out using a Telegan CO Sensor (Type 3F). Quoted values are the numerical averages of three independant determinations. 

Fig. 3.7 shows a comparison between a capillary thermostat in the right part of the figure and the ever more frequently used NTC temperature sensor whose analogue electrical signal can easily be processed by an electronic control system. The NTC sensor type is increasingly used, particularly in modern European machines that always have their own heater element and sometimes also an additional hot water connection. 

Company Name Sensor type Measurement range Power consumption Temperature range... 

Fence-associated sensors. Fence-associated sensors are either attached to an existing fence, or are installed in such a way as to create a fence. These sensors detect disturbances to the fence—such as those caused by an intruder attempting to climb the fence, or by an intruder attempting to cut or lift the fence fabric. Exterior fence-associated sensors include fence-disturbance sensors, taut-wire sensor fences, and electric field or capacitance sensors. Details on each of these sensor types are provided below. 

Free-standing sensors—These sensors, which include active infrared, passive infrared, bistatic microwave, monostatic microwave, dual-technology, and video motion detection (VMD) sensors, consist of individual sensor units or components that can be set up in a variety of configurations to meet a user s needs. They are installed aboveground, and depending on how they are oriented relative to each other, they can be used to establish a protected perimeter or a protected space. More details on each of these sensor types are provided below. 

If the oxygen sensitive dye is replaced by a pH sensitive dye, optical pH sensors can be produced. Thus miniaturization of these sensors is easy, and multisensing systems can be set up. Different sensor types for biotechnical application are described in the literature (e.g., ethanol and chloride sensors) [23,24]. 

Figure 15.9 Competitive morphine sensor response as a function of the morphine concentration (0-10 p-g/mL) present in the solution. Three sensor types were examined morphine molecular imprinted polymer (M-MIP), reference (O-MIP), and agarose-covered platinum electrode (Pt-Ag). Reprinted from Kriz and Mosbach (1995). Copyright 1995 Elsevier Science.

A wide number of sensor types have been described in the literature, from optical to mass spectrometry-based devices, but the sensors most commonly used in artificial tongues are electrochemical. 

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