Poisoning oxygen sensors

It should also be mentioned that low oil viscosity at low temperatures is desirable in the new small 4 cylinder and V-6 cylinder fuel economy automobiles ( 5, 6). This is to permit sufficient speed of engine cranking for cold weather starting at winter temperatures. Low oil volatility must be maintained to prevent oil misting and blowby from poisoning the catalyst system and oxygen sensors in the anti-pollution devices (7). 

Rettig, F., Moos, R. and Plog, C. (2004), Poisoning of temperature independent resistive oxygen sensors by sulfur dioxide. Journal of Electroceramics, 13(1-3), 733-8. 

Titanium dioxide is an n-type semiconductor that is used in thin-film oxygen and humidity sensors [155, 156]. Doping with other metal oxides (e.g., iron oxides) increases the sensitivity and selectivity of the titania oxygen sensors [157, 158]. In comparison to zirconia, titania sensors have a better resistance against lead poisoning. 

Optical sensors for oxygen measurement are attractive since they can be fast, do not consume oxygen and are not easily poisoned. The most common method adopted in construction is based on quenching of fluorescence from appropriate chemical species. The variation in fluorescence signal (I), or fluorescence decay time (x) with oxygen concentration [O2] is described by Stem-Volmer equation91 ... 

In the absence of sufficient oxygen, partial combustion of hydrocarbons occurs. The products may be carbon monoxide (a very poisonous gas) or carbon (which deposits on spark plugs, in the cylinder head, and on the pistons of automobile engines). Many modern automobile engines now use microcomputer chips and sensors to control the air supply and to optimize the fuel/02 ratio. The reactions of methane with insufficient oxygen are... 

Their operation depends on the absence of poisons such as lead compounds, and on a fuel injection system that provides an almost perfect stoichiometric ratio of fuel and oxygen to the engine this is achieved by a feedback system using a sensor that monitors the 02 content of the exhaust gases,... 

The carbon residue was readily removed by an oxygen treatment at moderate temperature. Almost no silicon or oxygen remained on the surface above 300K. This result cannot explain the poisoning effect of HMDS on platinum sensors used to detect methane in coal mine and other applications. It shows that the mechanism of decomposition of HMDS in the absence of oxygen and at the low... 

The limitation of NDIR technology for gas detection depends on the uniqueness of the absorption spectrum of a particular gas. IR sensors can detect gases in inert atmospheres (little or no oxygen present), are not susceptible to poisons, and can be made very specific to a particular target gas. 

Work with these types of electrodes enables to achieve steady-state current conditions within a short time-period. Primarily proposed for monitoring and control of blood and tissue oxygen tension [10], the electrode systems with selective membranes were manufactured and used in continuous oxygen measurement in a wide variety of aqueous solutions [11]. The sensors of this type, called Clark electrodes, are described in chapter 6 of this volume. Improvements designed for continuous monitoring in industrial bioreactors may be found in section 6 of chapter 3. The most important feature of the membranes used in these sensors is their selectivity which prevents poisoning the electrode system and deteriorating the adherent electrolyte solution. 

The so-caUed Lambda probe to this day is the most successful and most widespread chemical sensor. It is used in all modern motor vehicles, where it serves to control the oxygen content in combustion gas. The combustion process in the motor is regulated to minimize the output of poisonous carbon monoxide. 

An oxygen electrode (VWR 0X630) was purchased from VWR and connected via a valve to the permeate reservoir of a permeation test system. The probe has a 95% response in 30 seconds at pressures ranging from 0 to 25 psi. Further, the manufacturer claims that this sensor is not poisoned when in contact... 

Gas sensors are devices which detect or monitor a desired component or components in gases, and quantitatively convert the information to an electric signal. The component(s) may be combustible gases, oxygen, water (humidity), poisonous gases, etc. 

NDIR combustible gas sensors have a number of other advantages when compared to pellis-tor type sensors. NDIR sensors do not have a flame arrestor that limits the ability of large molecules to diffuse into the optical sensing chamber. NDIR sensors do not require oxygen. They are also not subject to damage due to exposure to sensor poisons. Finally, unlike pellistor type sensors, they can be used for measurement of high concentration combustible gas above the 100 percent LEL concentration. 

Cobalt-based macrocyclic complexes are some of the catalysts that exhibit significant catalytic activity against DO. Vitamin B12 is a cobalt-based complex and inherits excellent electrocatalytic properties. It can be easily screen printed to modify the electrode providing DO sensors better than the Clark-type electrode. The latter should be covered with a permeable membrane and must be properly maintained. Modifying the electrode with vitamin B12 creates a membrane-free DO sensor. Tedious maintenance is not required with this kind of sensor. Moreover, poisoning of the membrane is not an issue anymore. The electrochemical behavior of the vitamin Bi2-modified electrode involved in the reduction of oxygen can be explained by the following equations ... 

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