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Helium Analyzer
A Helium analyzer is an instrument used to identify the presence and concentration of helium in a mixture of gases. In Technical diving where breathing gas mixtures known as Trimix comprising oxygen, helium and nitrogen are used, it is necessary to know the fraction of helium in the mixture to reliably calculate decompression schedules for dives using that mixture. Thermal conductivity principle Portable instruments for the analysis of helium content of breathing gas mixtures may be based on a thermal conductivity sensor ( katharometer). These sensors can be very stable and maintenance free and also highly reliable and accurate. A typical thermal helium analyser comprises two chambers, each with an identical thermal conductivity sensor. One chamber is sealed and is filled with pure helium as the reference gas, and the other receives the sample gas. The difference in thermal conductivity of the reference and sample gases is measured and converted into a concentration valu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gas Blending Oxygen And Helium Analyser
Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or compound molecules made from a variety of atoms (e.g. carbon dioxide). A gas mixture, such as air, contains a variety of pure gases. What distinguishes a gas from liquids and solids is the vast separation of the individual gas particles. This separation usually makes a colourless gas invisible to the human observer. The gaseous state of matter occurs between the liquid and plasma states, the latter of which provides the upper temperature boundary for gases. Bounding the lower end of the temperature scale lie degenerative quantum gases which are gaining increasing attention. High-density atomic gases super-cooled to very low temperatures are classified by their statistical behavior as either Bose gases or Fermi gases. For a comprehensive lis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Breathing Gas
A breathing gas is a mixture of gaseous chemical elements and compounds used for respiration. Air is the most common and only natural breathing gas, but other mixtures of gases, or pure oxygen, are also used in breathing equipment and enclosed habitats such as scuba equipment, surface supplied diving equipment, recompression chambers, high-altitude mountaineering, high-flying aircraft, submarines, space suits, spacecraft, medical life support and first aid equipment, and anaesthetic machines. Oxygen is the essential component for any breathing gas, at a partial pressure of between roughly 0.16 and 1.60 bar at the ambient pressure. The oxygen is usually the only metabolically active component unless the gas is an anaesthetic mixture. Some of the oxygen in the breathing gas is consumed by the metabolic processes, and the inert components are unchanged, and serve mainly to dilute the oxygen to an appropriate concentration, and are therefore also known as diluent gases. Most ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gas Blending
Gas blending is the process of mixing gases for a specific purpose where the composition of the resulting mixture is specified and controlled. A wide range of applications include scientific and industrial processes, food production and storage and breathing gases. Gas mixtures are usually specified in terms of molar gas fraction (which is closely approximated by volumetric gas fraction for many permanent gases): by percentage, parts per thousand or parts per million. Volumetric gas fraction converts trivially to partial pressure ratio, following Dalton's law of partial pressures. Partial pressure blending at constant temperature is computationally simple, and pressure measurement is relatively inexpensive, but maintaining constant temperature during pressure changes requires significant delays for temperature equalization. Blending by mass fraction is unaffected by temperature variation during the process, but requires accurate measurement of mass or weight, and calculation of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxygen Sensor
An oxygen sensor (or lambda sensor, where lambda refers to air–fuel equivalence ratio, usually denoted by λ) or probe or sond, is an electronic device that measures the proportion of oxygen (O2) in the gas or liquid being analysed. It was developed by Robert Bosch GmbH during the late 1960s under the supervision of Dr. Günter Bauman. The original sensing element is made with a thimble-shaped zirconia ceramic coated on both the exhaust and reference sides with a thin layer of platinum and comes in both heated and unheated forms. The planar-style sensor entered the market in 1990 and significantly reduced the mass of the ceramic sensing element, as well as incorporating the heater within the ceramic structure. This resulted in a sensor that started sooner and responded faster. The most common application is to measure the exhaust-gas concentration of oxygen for internal combustion engines in automobiles and other vehicles in order to calculate and, if required, dynamically a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxygen Analyser
An electro-galvanic fuel cell is an electrochemical device which consumes a fuel to produce an electrical output by a chemical reaction. One form of electro-galvanic fuel cell based on the oxidation of lead is commonly used to measure the concentration of oxygen gas in underwater diving and medical breathing gases. Electronically monitored or controlled diving rebreather systems, saturation diving systems, and many medical life-support systems use galvanic oxygen sensors in their control circuits to directly monitor oxygen partial pressure during operation. They are also used in oxygen analysers in recreational, technical diving and surface supplied mixed gas diving to analyse the proportion of oxygen in a nitrox, heliox or trimix breathing gas before a dive. These cells are lead/oxygen galvanic cells where oxygen molecules are dissociated and reduced to hydroxyl ions at the cathode. The ions diffuse through the electrolyte and oxidize the lead anode. A current proportional to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Decompression Algorithms
There are several categories of decompression equipment used to help divers decompress, which is the process required to allow divers to return to the surface safely after spending time underwater at higher ambient pressures. Decompression obligation for a given dive profile must be calculated and monitored to ensure that the risk of decompression sickness is controlled. Some equipment is specifically for these functions, both during planning before the dive and during the dive. Other equipment is used to mark the underwater position of the diver, as a position reference in low visibility or currents, or to assist the diver's ascent and control the depth. Decompression may be shortened ("accelerated") by breathing an oxygen-rich "decompression gas" such as a nitrox blend or pure oxygen. The high partial pressure of oxygen in such decompression mixes produces the effect known as the oxygen window. This decompression gas is often carried by scuba divers in side-slung cylinde ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Katharometer
The thermal conductivity detector (TCD), also known as a katharometer, is a bulk property detector and a chemical specific detector commonly used in gas chromatography. This detector senses changes in the thermal conductivity of the column eluent and compares it to a reference flow of carrier gas. Since most compounds have a thermal conductivity much less than that of the common carrier gases of helium or hydrogen, when an analyte elutes from the column the effluent thermal conductivity is reduced, and a detectable signal is produced. Operation The TCD consists of an electrically heated filament in a temperature-controlled cell. Under normal conditions there is a stable heat flow from the filament to the detector body. When an analyte elutes and the thermal conductivity of the column effluent is reduced, the filament heats up and changes resistance. This resistance change is often sensed by a Wheatstone bridge circuit which produces a measurable voltage change. The column effluent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Conductivity Analyser
A thermal column (or thermal) is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example of convection, specifically atmospheric convection. Thermals on Earth The Sun warms the ground, which in turn warms the air directly above. The warm air near the surface expands, becoming less dense than the surrounding air. The lighter air rises and cools due to its expansion in the lower pressure at higher altitudes. It stops rising when it has cooled to the same temperature, thus density, as the surrounding air. Associated with a thermal is a downward flow surrounding the thermal column. The downward-moving exterior is caused by colder air being displaced at the top of the thermal. The size and strength of thermals are influenced by the properties of the lower atmosphere (the ''troposphere''). When the air is cold, bubbles of warm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Decompression (diving)
The decompression of a diver is the reduction in ambient pressure experienced during ascent from depth. It is also the process of elimination of dissolved inert gases from the diver's body, which occurs during the ascent, largely during pauses in the ascent known as decompression stops, and after surfacing, until the gas concentrations reach equilibrium. Divers breathing gas at ambient pressure need to ascend at a rate determined by their exposure to pressure and the breathing gas in use. A diver who only breathes gas at atmospheric pressure when free-diving or snorkelling will not usually need to decompress, Divers using an atmospheric diving suit do not need to decompress as they are never exposed to high ambient pressure. When a diver descends in the water, the hydrostatic pressure, and therefore the ambient pressure, rises. Because breathing gas is supplied at ambient pressure, some of this gas dissolves into the diver's blood and is transferred by the blood to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at seventh in total abundance in the Milky Way and the Solar System. At standard temperature and pressure, two atoms of the element bond to form N2, a colorless and odorless diatomic gas. N2 forms about 78% of Earth's atmosphere, making it the most abundant uncombined element. Nitrogen occurs in all organisms, primarily in amino acids (and thus proteins), in the nucleic acids ( DNA and RNA) and in the energy transfer molecule adenosine triphosphate. The human body contains about 3% nitrogen by mass, the fourth most abundant element in the body after oxygen, carbon, and hydrogen. The nitrogen cycle describes the movement of the element from the air, into the biosphere and organic compounds, then back into the atmosphere. Many industrially ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
