Sensor monoxide

Afterburn Control. Afterburn is the term for carbon monoxide burning downstream of the regenerator this causes an increase in temperature upstream of the expander. Temperature sensors in the gas stream cause the brake to energize. This provides sufficient resisting torque to prevent acceleration until the afterburn is brought under control by water or steam injection. 

Carbon monoxide and carbon dioxide can be measured using the FTIR techniques (Fourier transform infrared techniques see the later section on the Fourier transform infrared analyzer). Electrochemical cells have also been used to measure CO, and miniaturized optical sensors are available for CO 2 monitoring. 

Applicability of Semiconductor Gas Sensors Research into the applications of this type of sensor has mainly been concerned with measuring carbon monoxide concentration in flue gases. Tests show that sensors follow the concentration of carbon monoxide in the flue gas. Improvement in sensor performance has resulted with the introduction of a catalytic additive (palladium or... 

Other usefiil gas sensors include the potentiometric ammonia (64) or hydrogen cyanide probes (65), and amperometric carbon monoxide (66) and nitrogen dioxide (67) devices. The hydrogen cyanide probe is an example of a modem device that relies on changes in the conductivity of electropolymerized film (polyanihne) in the presence of a given gas. 

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. 

Up to now, sensors using this parameter have not been taken into consideration, as they are generally not selective. Water for instance is traceable in air because its velocity of sound is significantly higher. The VOS of carbon dioxide is just around 1/3 the VOS of air. In a mixture of air, water and C02 none of the compounds can be quantified. As the VOS of carbon monoxide is similar to that of air, CO cannot be quantifiedby this method either. Hence, sensors based on acoustic principles cannot be taken into consideration neither for the measurement of single species in a flue gas flow nor for the identification of fuel gases. 

The well-known step function of 7-probes as they are commonly mounted in combustion engines of motor vehicles is much smaller with this probe and is shifted to higher air ratios. The assumed reason are reactions with intermediate combustion products, free radicals and carbon monoxide on the sensor surface whose intensity increases with lowering air ratios down to stoichiometric level. A solution for the set up based on this sensor is presented further below. 

Fig. 3.29 Resistances of the 38 sensor segments of a Sn02-microarray equipped with Si02-membrane during alternating exposure to carbon monoxide contaminated humid air and clean air with the same relative humidity...

Tab. 5.9 Gas sensors and sensor system for detection of carbon monoxide.

Multi-sensor fire detectors provide faster detection with fewer false alarms. These sensors are capable of monitoring the environment for multiple purposes, e.g. carbon monoxide concentration, concentration of flammable gases and indoor air quality, too. 

Small, portable sensors are now available to monitor the air we breathe for such toxins as carbon monoxide, CO. As soon as the air contains more than a critical concentration of CO, the sensor alerts the householder, who then opens a window or identifies the source of the gas. 

The model analytes, which were used to show the sensor performance of the microsystems include carbon monoxide, CO, and methane, CH4. The sensor microsystems were designed for practical applications, such as environmental monitoring, industrial safety applications or household surveillance, which implies that oxygen and water vapors are present under normal operating conditions. In the following, a brief overview of the relevant gas sensor mechanisms focused on nano crystalline tin-oxide thick-film layers will be given. 

The model sensitive layer, which will be used for gas sensor performance tests throughout this book, was Sn02 that has been doped with 0.2 wt % Pd. The minute Pd-content leads to a better sensitivity to carbon monoxide. The larger response is a consequence of the increased reaction rate. For the sensor arrays in Chap. 6, two additional materials have been prepared. Pure tin oxide shows a good sensor response... 

PR Tsai, I.C. Chen, and C.J. Ho. Ultralow power carbon monoxide microsensor by micromachining techniques , Sensors and Actuators B76 (2001), 380-387. 

Hematite is used to coat the red emiting phosphor, Y2O2EU, which is used in cathode ray tubes (Franz et al., 1993 Merckhi and Feldmann, 2000). Hematite is also used in sensors for the detection of hydrocarbon gases and carbon monoxide. The sensitivity of the sensor can be improved by sintering the oxide with 0.09 mol ° mol Al at 850 °C (Han et al., 2001 and references therein). 

Elemental composition C 42.88%, O 57.12%. Carbon monoxide may be identified and determined quantitatively at low ppm level by infrared sensors. Such CO detectors are commercially available. Also, it can be analyzed by GC using TCD or FID or by GC/MS. The characteristic ion mass for CO identification is 28 (same as N2 or ethylene, both of which can interfere). 

Recent emission control system development in the automotive industry has been directed mainly towards the use of three-way or dual bed catalytic converters, This type of converter system not only oxidizes the hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas but will also reduce the nitrous oxides (NO ). An integral part of this type of system is the exhaust oxygen sensor which is used to provide feedback for closed loop control of the air-fuel ratio. This is necessary since this type of catalytic converter system operates efficiently only when the composition of the exhaust gas is very near the stoichiometric point. 

Sachse, G. W., G. F. Hill, L. O. Wade, and M. G. Perry, Fast-Response, High-Precision Carbon Monoxide Sensor Using a Tunable Diode Laser Absorption Technique, J. Geophys. Res., 92, 2071-2081 (1987). 

As mentioned earlier, the oxidation of carbon monoxide and hydrocarbons should be achieved simultaneously with the reduction of nitrogen oxides. However, the first reaction needs oxygen in excess, whereas the second one needs a mixture (fuel-oxygen) rich in fuel. The solution was found with the development of an oxygen sensor placed at exhaust emissions, which would set the air-to-fuel ratio at the desired value in real time. So, the combination of electronics and catalysis and the progress in these fields led to better control of the exhaust emissions from automotive vehicles. 

Recent Developments in Electrochemical Solid Polymer Electrolyte Sensor Cells for Measuring Carbon Monoxide and Oxides of Nitrogen... 

Each of these considerations must be resolved before a personal monitor can be applied to air pollution research and characterization studies. Some advances have been made for carbon monoxide, volatile organic compounds, acid aerosols, and particulate matter (PM-10 and RSP these represent the masses of all particles collected in samplers with 50% cut sizes of 10 and 25 xm, respectively) and its components (12, 22-31). Each advance is still undergoing development, and further advances can be anticipated for these as well as for other pollutants. The next generation of monitors will probably include devices for some pollutants that incorporate the use of microsensors. Currently, microsensors are being examined for detection of nitrogen dioxide and ozone, but the range of sensors available suggests that they can be used for a number of compounds (10, 32) ... 

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