Air–fuel ratio meter
An air–fuel ratio meter monitors the air–fuel ratio of an internal combustion engine. Called air–fuel ratio gauge, air–fuel meter, or air–fuel gauge, it reads the voltage output of an oxygen sensor, sometimes called AFR sensor or lambda sensor, whether it be from a narrow band or wide band oxygen sensor. The original narrow-band oxygen sensors became factory installed standard in the late 1970s and early 1980s. In recent years a newer and much more accurate wide-band sensor, though more expensive, has become available. Most stand-alone narrow-band meters have 10 LEDs and some have more. Common, narrow band meters in round housings with the standard mounting 2 1/16" and 2 5/8" diameters, as other types of car'gauges'; these have 10 or 20 LEDs. Analogue'needle' style gauges are available; as stated above, there are wide-band meters that are mounted in housings. Nearly all of these show the air–fuel ratio on a numeric display since the wide-band sensors provide a much more accurate reading; as wide-band sensors use more accurate electronics, these meters are more expensive.
Determining the condition of the oxygen sensor: A malfunctioning oxygen sensor will result in air–fuel ratios that respond more to changing engine conditions. A damaged or defective sensor may lead to increased fuel consumption and increased pollutant emissions as well as decreased power and throttle response. Most engine management systems will detect a defective oxygen sensor. Reducing emissions: Keeping the air–fuel mixture near the stoichiometric ratio of 14.7:1 allows the catalytic converter to operate at maximum efficiency. Fuel economy: An air–fuel mixture leaner than the stoichiometric ratio will result in near-optimal fuel mileage, costing less per distance traveled and producing the least amount of CO2 emissions. However, from the factory, cars are designed to operate at the stoichiometric ratio to maximize the efficiency and life of the catalytic converter. While it may be possible to run smoothly at mixtures leaner than the stoichiometric ratio, manufacturers must focus on emissions and catalytic converter life as a higher priority due to U.
S. EPA regulations. Engine performance: Carefully mapping out air–fuel ratios throughout the range of rpm and manifold pressure will maximize power output in addition to reducing the risk of detonation. Lean mixtures improve the fuel economy but cause sharp rises in the amount of nitrogen oxides. If the mixture becomes too lean, the engine may fail to ignite, causing misfire and a large increase in unburned hydrocarbon emissions. Lean mixtures burn hotter and may cause rough idle, hard starting and stalling, can damage the catalytic converter, or burn valves in the engine; the risk of spark knock/engine knocking is increased when the engine is under load. Mixtures that are richer than stoichiometric allow for greater peak engine power when using vaporized liquid fuel due to the mixture not being able to reach a homogenized state so extra fuel is added to ensure all oxygen is burned producing maximum power; the ideal mixture in this type of operation depends on the individual engine. For example, engines with forced induction such as turbochargers and superchargers require a richer mixture under wide open throttle than aspirated engines.
Forced induction engines can be catastrophically damaged by burning too lean for too long. The leaner the air–fuel mixture, the higher the combustion temperature is inside the cylinder. Too high a temperature will destroy an engine – melting the pistons and valves; this can happen if one ports the head and/or manifolds or increase boost without compensating by installing larger or more injectors, and/or increasing the fuel pressure to a sufficient level. Conversely, engine performance can be lessened by increasing fueling without increasing air flow into the engine. Furthermore, if an engine is leaned to the point where its exhaust gas temperature starts to fall, its cylinder head temperature will fall; this is only recommended in the cruising configuration, never when accelerating hard, but is becoming popular in aviation circles, where the appropriate engine monitoring gauges are fitted and the fuel air mixture can be manually adjusted. Cold engines typically require more fuel and a richer mixture when first started, because fuel does not vaporize as well when cold and therefore requires more fuel to properly "saturate" the air.
Rich mixtures burn slower and decrease the risk of spark knock/engine knocking when the engine is under load. However, rich mixtures increase carbon monoxide emissions; the early introduction of the oxygen sensor came about in the late 1970s. Since zirconia has been the material of choice for its construction; the zirconia O2 sensor produces its own voltage. The varying voltage will display on a scope as a waveform somewhat resembling a sine wave when in closed loop control; the actual voltage, generated is a measure of the oxygen, needed to complete the combustion of the CO and HC present at the sensor tip. The stoichiometric air-fuel ratio mixture ratio for gasoline engine is the theoretical air-fuel ratio at which all of the fuel will react with all of the available oxygen resulting in complete combustion. At or near this ratio, the combustion process produces the best balance between power and low emissions. At the stoichiometric air-fuel ratio, the generated O2 sensor voltage is about 450 mV.
The Engine Control Module recognizes a rich condition above the 450 mV level, a lean condi
Carbon monoxide detector
A carbon monoxide detector or CO detector is a device that detects the presence of the carbon monoxide gas in order to prevent carbon monoxide poisoning. In the late 1990s Underwriters Laboratories changed their definition of a single station CO detector with a sound device in it to a carbon monoxide alarm; this applies to all CO safety alarms. CO is a colorless and odorless compound produced by incomplete combustion of carbon-containing materials, it is referred to as the "silent killer" because it is undetectable by humans without using detection technology and, in a study by Underwriters Laboratories, "Sixty percent of Americans could not identify any potential signs of a CO leak in the home". Elevated levels of CO can be dangerous to humans depending on the amount present and length of exposure. Smaller concentrations can be harmful over longer periods of time while increasing concentrations require diminishing exposure times to be harmful. CO detectors are designed to measure CO levels over time and sound an alarm before dangerous levels of CO accumulate in an environment, giving people adequate warning to safely ventilate the area or evacuate.
Some system-connected detectors alert a monitoring service that can dispatch emergency services if necessary. While CO detectors do not serve as smoke detectors and vice versa, dual smoke/CO detectors are sold. Smoke detectors warn of smoldering or flaming fires by detecting the smoke they generate, whereas CO detectors detect and warn people about dangerous CO buildup caused, for example, by a malfunctioning fuel-burning device. In the home, some common sources of CO include open flames, space heaters, water heaters, blocked chimneys or running a car or grill inside a garage; the devices, which retail for $15–$60 USD and are available, can either be battery-operated or AC powered. Battery lifetimes have been increasing as the technology has developed and certain battery-powered devices now advertise a battery lifetime of up to 10 years. All CO detectors have "test" buttons like smoke detectors. CO detectors can be placed near the ceiling or near the floor because CO is close to the same density as air.
Since CO is colorless and odorless, detection in a home environment is impossible without such a warning device. It is a toxic inhalant and attaches to the hemoglobin with an affinity 200x stronger than oxygen, producing inadequate amounts of oxygen traveling through the body; when carbon monoxide detectors were introduced into the market, they had a limited lifespan of 2 years. However technology developments have increased this and many now advertise up to 10 years. Newer models are designed to signal a need to be replaced after that time-span although there are many instances of detectors operating far beyond this point. According to the 2005 edition of the carbon monoxide guidelines, NFPA 720, published by the National Fire Protection Association, sections 184.108.40.206 and 220.127.116.11, all CO detectors “shall be centrally located outside of each separate sleeping area in the immediate vicinity of the bedrooms,” and each detector “shall be located on the wall, ceiling or other location as specified in the installation instructions that accompany the unit.”
According to the 2009 edition of the IRC, published by the International Code Council, section R315.1, "For new construction, an approved carbon monoxide alarm shall be installed outside of each separate sleeping area in the immediate vicinity of the bedrooms in dwelling units within which fuel-fired appliances are installed and in dwelling units that have attached garages", section 315.2, "Where work requiring a permit occurs in existing dwellings that have attached garages or in existing dwellings within which fuel-fired appliances exist, carbon monoxide alarms shall be provided in accordance with Section R315.1." Installation locations vary by manufacturer. Manufacturers’ recommendations differ to a certain degree based on research conducted with each one’s specific detector. Therefore, make sure to read the provided installation manual for each detector before installing. CO detectors are available as system-connected, monitored devices. System-connected detectors, which can be wired to either a security or fire panel, are monitored by a central station.
In case the residence is empty, the residents are sleeping or occupants are suffering from the effects of CO, the central station can be alerted to the high concentrations of CO gas and can send the proper authorities to investigate. The gas sensors in CO alarms have a limited and indeterminable life span two to five years; the test button on a CO alarm only tests the circuitry, not the sensor. CO alarms should be tested with an external source of calibrated test gas, as recommended by the latest version of NFPA 720. Alarms over five years old should be replaced but they should be checked on installation and at least annually during the manufacturers warranty period. Early designs were a white pad which would fade to a brownish or blackish color if carbon monoxide was present; such chemical detectors were cheap and were available, but only give a visual warning of a problem. As carbon monoxide related deaths increased during the 1990s, audible alarms became standard; the alarm points on carbon monoxide detectors are not a simple alarm level but are a concentration-time function.
At lower concentrations the detector will not sound an alarm for many tens of minutes. At 400 parts per million, the alarm will so
Variable reluctance sensor
A variable reluctance sensor is a transducer that measures changes in magnetic reluctance. When combined with basic electronic circuitry, the sensor detects the change in presence or proximity of ferrous objects. With more complex circuitry and the addition of software and specific mechanical hardware, a VR sensor can provide measurements of linear velocity, angular velocity and torque. A VR sensor used as a simple proximity sensor can determine the position of a mechanical link in a piece of industrial equipment. A Crankshaft position sensor is used to provide the angular position of the crankshaft to the Engine control unit; the Engine control unit can calculate engine speed. Speed sensors used in automobile transmissions, are used to measure the rotational speed of shafts within the transmission; the Engine control unit or Transmission control unit uses these sensors to determine when to shift from one gear to the next. A pickup used in an electric guitar detect vibrations of the metallic "strings".
See Pickup for details of this application. This sensor consists of a permanent magnet, a ferromagnetic pole piece, coil of wire. VR sensor interface circuits VR sensors need waveform shaping for their output to be digitally readable; the normal output of a VR sensor is an analog signal, shaped much like a sine wave. The frequency and amplitude of the analog signal is proportional to the target's velocity; this waveform needs to be squared up, flattened off by a comparator like electronic chip to be digitally readable. While discrete VR sensor interface circuits can be implemented, the semiconductor industry offers integrated solutions. Examples are the MAX9924 to MAX9927 VR sensor interface IC from Maxim Integrated products, LM1815 VR sensor amplifier from National Semiconductor and NCV1124 from ON semiconductor. An integrated VR sensor interface circuit like the MAX9924 features a differential input stage to provide enhanced noise immunity, Precision Amplifier and Comparator with user enabled Internal Adaptive Peak Threshold or user programmed external threshold to provide a wide dynamic range and zero-crossing detection circuit to provide accurate phase Information.
To measure angular position or rotational speed of a shaft, a toothed ring made of ferrous material can be attached to the shaft. As the teeth of the rotating wheel pass by the face of the magnet, the amount of magnetic flux passing through the magnet and the coil varies; when the gear tooth is close to the sensor, the flux is at a maximum. When the tooth is further away, the flux drops off; the moving target results in a time-varying flux. Subsequent electronics are used to process this signal to get a waveform that can be more counted and timed; this system has been employed in ABS braking. By attaching two reluctor rings to a shaft, the torque can be measured; the tooth spacing on reluctor rings may be uneven. Although VR sensors are based on mature technology, they still offer several significant advantages; the first is low cost - coils of wire and magnets are inexpensive. The low cost of the transducer is offset by the cost of the additional signal-processing circuitry needed to recover a useful signal.
And because the magnitude of the signal developed by the VR sensor is proportional to target speed, it is difficult to design circuitry to accommodate very-low-speed signals. A given VR-sensing system has a definite limit as to how slow the target can move and still develop a usable signal. An alternative but more expensive technology is Hall effect sensor. Hall effect sensors are true zero-rpm sensors and supply information when there's no transmission motion at all. One area in which VR sensors excel, however, is in high-temperature applications; because operating temperature is limited by the characteristics of the materials used in the device, with appropriate construction VR sensors can be made to operate at temperatures in excess of 300 °C. An example of such an extreme application is sensing the turbine speed of a jet engine or engine cam shaft and crankshaft position control in an automobile
Catalytic bead sensor
A catalytic bead sensor is a type of sensor, used for combustible gas detection from the family of gas sensors known as pellistors. The catalytic bead sensor consists of two coils of fine platinum wire each embedded in a bead of alumina, connected electrically in a Wheatstone bridge circuit. One of the pellistors is impregnated with a special catalyst which promotes oxidation whilst the other is treated to inhibit oxidation. Current is passed through the coils so that they reach a temperature at which oxidation of a gas occurs at the catalysed bead. Passing combustible gas raises the temperature further which increases the resistance of the platinum coil in the catalysed bead, leading to an imbalance of the bridge; this output change is linear, for most gases, up to and beyond 100% LEL, response time is a few seconds to detect alarm levels, at least 12% oxygen by volume is needed for the oxidation. Catalyst poisoning - because of the direct contact of the gas with the catalytic surface it may be deactivated in some circumstances.
Sensor drift - Decreased sensitivity may occur depending on operating and ambient conditions. Modes of failure - which include poisoning and sinter blockage, they become apparent during routine maintenance checking. List of sensors
An electrolyte is a substance that produces an electrically conducting solution when dissolved in a polar solvent, such as water. The dissolved electrolyte separates into cations and anions, which disperse uniformly through the solvent. Electrically, such a solution is neutral. If an electric potential is applied to such a solution, the cations of the solution are drawn to the electrode that has an abundance of electrons, while the anions are drawn to the electrode that has a deficit of electrons; the movement of anions and cations in opposite directions within the solution amounts to a current. This includes most soluble salts and bases; some gases, such as hydrogen chloride, under conditions of high temperature or low pressure can function as electrolytes. Electrolyte solutions can result from the dissolution of some biological and synthetic polymers, termed "polyelectrolytes", which contain charged functional groups. A substance that dissociates into ions in solution acquires the capacity to conduct electricity.
Sodium, chloride, calcium and phosphate are examples of electrolytes. In medicine, electrolyte replacement is needed when a person has prolonged vomiting or diarrhea, as a response to strenuous athletic activity. Commercial electrolyte solutions are available for sick children and athletes. Electrolyte monitoring is important in the treatment of bulimia; the word electrolyte derives from the Greek lytós, meaning "able to be untied or loosened". Svante Arrhenius put forth, in his 1884 dissertation, his explanation of the fact that solid crystalline salts disassociate into paired charged particles when dissolved, for which he won the 1903 Nobel Prize in Chemistry. Arrhenius's explanation was that in forming a solution, the salt dissociates into charged particles, to which Michael Faraday had given the name "ions" many years earlier. Faraday's belief had been. Arrhenius proposed that in the absence of an electric current, solutions of salts contained ions, he thus proposed. Electrolyte solutions are formed when a salt is placed into a solvent such as water and the individual components dissociate due to the thermodynamic interactions between solvent and solute molecules, in a process called "solvation".
For example, when table salt, NaCl, is placed in water, the salt dissolves into its component ions, according to the dissociation reaction NaCl → Na+ + Cl−It is possible for substances to react with water, producing ions. For example, carbon dioxide gas dissolves in water to produce a solution that contains hydronium and hydrogen carbonate ions. Molten salts can be electrolytes as, for example, when sodium chloride is molten, the liquid conducts electricity. In particular, ionic liquids, which are molten salts with melting points below 100 °C, are a type of conductive non-aqueous electrolytes and thus have found more and more applications in fuel cells and batteries. An electrolyte in a solution may be described as "concentrated" if it has a high concentration of ions, or "diluted" if it has a low concentration. If a high proportion of the solute dissociates to form free ions, the electrolyte is strong; the properties of electrolytes may be exploited using electrolysis to extract constituent elements and compounds contained within the solution.
Alkaline earth metals form hydroxides that are strong electrolytes with limited solubility in water, due to the strong attraction between their constituent ions. This limits their application to situations. In physiology, the primary ions of electrolytes are sodium, calcium, chloride, hydrogen phosphate, hydrogen carbonate; the electric charge symbols of plus and minus indicate that the substance is ionic in nature and has an imbalanced distribution of electrons, the result of chemical dissociation. Sodium is the main electrolyte found in extracellular fluid and potassium is the main intracellular electrolyte. All known higher lifeforms require a subtle and complex electrolyte balance between the intracellular and extracellular environments. In particular, the maintenance of precise osmotic gradients of electrolytes is important; such gradients affect and regulate the hydration of the body as well as blood pH, are critical for nerve and muscle function. Various mechanisms exist in living species that keep the concentrations of different electrolytes under tight control.
Both muscle tissue and neurons are considered electric tissues of the body. Muscles and neurons are activated by electrolyte activity between the extracellular fluid or interstitial fluid, intracellular fluid. Electrolytes may enter or leave the cell membrane through specialized protein structures embedded in the plasma membrane called "ion channels". For example, muscle contraction is dependent upon the presence of calcium and potassium. Without sufficient levels of these key electrolytes, muscle weakness or severe muscle contractions may occur. Electrolyte balance is maintained by oral, or in emergencies, intravenous intake of electrolyte-containing substances, is regulated by hormones, in general with the kidneys flushing out excess levels. In humans, electrolyte homeostasis is regulated by hormones such as antidiuretic hormones and parathyroid hormones. Serious electrol
Curb feelers or curb finders are springs or wires installed on a vehicle which act as "whiskers" to alert drivers when they are at the right distance from the curb while parking. The devices are fitted low on the body, close to the wheels; as the vehicle approaches the curb, the protruding feelers scrape against the curb, making a noise and alerting the driver in time to avoid damaging the wheels or hubcaps. The feelers do not break easily. Curb feelers are still used on some hot rods, they are popular for cars with whitewall tires, which lose their white coating when scraped against the curb. Sometimes curb feelers are found only on the passenger side of the car, since, most near the curb when parking. Sometimes they are added only next to the front wheels; some curb feelers have a single wire or spring, while others have two to increase the area that can be protected. Any particular car may have just one curb feeler installed or more if attached near the front and rear, as well as on both sides of the vehicle.
Recreational vehicles sometimes have rubber feelers or metal, antenna-like rods mounted on the lower part of the body that act as feelers so that drivers are warned if they are approaching a curb or other obstruction, thus reducing the chances of gouging or cutting the tire sidewalls and increasing the safety of vehicle operation. Buses are sometimes fitted with curb feelers, which can assist the driver in ensuring that the bus is close enough to the curb to allow passengers to step to and from the curb easily. Today, the U. S. Department of Labor Mine Safety and Health Administration mentions that users of heavy equipment can benefit from an analogous accessory: In the 1950s, cars were equipped with curb feelers... Using a piece of 48 inches conveyor belt, 4-to-5-foot long by 4 to 6 inches wide and a couple of pieces of angle iron, you can make a pinch-point feeler, a warning device for the corners of a continuous miner; this will give a warning nudge to anyone in the danger area, giving him or her about a two-foot running start to stop the machine or to yell at the operator to stop.
The belting is stiff enough to hold its shape but flexible enough to give if it runs into a miner or vice versa. The flexibility allows this "curb feeler" to drag against the rib or be smacked by a shuttle car with little or no damage. A little spray from a can of reflective paint will make the belt a visual warning device as well. One or two on each corner will put as many as you want. Curb feelers based on optical technology are designed to function the same way but work in the proximity of an obstruction rather than having to come into physical contact with it; as described by one United States patent: An electronic curb feeler system uses two pairs of optical sensor units to detect an object located near the front end of a vehicle during parking. One pair of optical sensor units detects an object directly in front of a left portion of the front end of the vehicle while another pair of optical sensors detects an object directly in front of a right portion of the front end of the vehicle. By supplying the operator of the vehicle with the location of the object as well as the exact distance the object is from the front end of the vehicle the operator can avoid hitting the object while parking close to the object.
Devices such as this, simpler electronic devices similar to the original wire curb feelers used on cars, are used in the design of various mobile robotic devices. One robotics company that does work for the United States Department of Defense uses laser-assisted curb feeler technology. Fender skirts
A hydrophone is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducer that generates an electric potential when subjected to a pressure change, such as a sound wave; some piezoelectric transducers can serve as a sound projector, but not all have this capability, some may be destroyed if used in such a manner. A hydrophone can detect airborne sounds, but will be insensitive because it is designed to match the acoustic impedance of water, a denser fluid than air. Sound travels 4.3 times faster in water than in air, a sound wave in water exerts a pressure 60 times that exerted by a wave of the same amplitude in air. A standard microphone can be buried in the ground, or immersed in water if it is put in a waterproof container, but will give poor performance due to the bad acoustic impedance match; the first hydrophones consisted of a tube with a thin membrane covering the submerged end and the observer's ear on the other end.
The design of effective hydrophones must take into account the acoustic resistance of water, 3750 times that of air. The American Submarine Signaling Company developed a hydrophone to detect underwater bells rung from lighthouses and lightships. The case was a hollow brass disc 35 centimetres in diameter. On one face was a 1 millimetre thick brass diaphragm, coupled by a short brass rod to a carbon microphone. Early in the war the French President Poincaré provided Paul Langevin with the facilities needed to work on a method to locate submarines by the echos from sound pulses, they developed a piezoelectric hydrophone by increasing the power of the signal with a vacuum tube amplifier. The same piezoelectric plate could be vibrated by an electrical oscillator to produce the sound pulses. In the war the British Admiralty belatedly convened a scientific panel to advise on how to combat U-boats. It included the Australian physicist William Henry Bragg and the New Zealand physicist Sir Ernest Rutherford.
They concluded. Rutherford's research produced his sole patent for a hydrophone. Bragg took the lead in July 1916 he moved to the Admiralty hydrophone research establishment at Hawkcraig on the Firth of Forth. The scientists set two goals: to develop a hydrophone that could hear a submarine despite the racket produced by a patrol ship carrying the hydrophone and to develop a hydrophone that could reveal the bearing of the submarine. A bidirectional hydrophone was invented at East London College, they mounted a microphone on each side of a diaphragm in a cylindrical case, when the sounds heard from both microphones have the same intensity the microphone is in line with the sound source. Bragg's laboratory made such a hydrophone directional by mounting a baffle in front of one side of the diaphragm. It took months to discover that effective baffles must contain a layer of air. In 1918 airships of the Royal Naval Air Service engaged in anti-submarine warfare experimented by trailing dipped hydrophones.
Bragg found it inferior to British models. By the end of the war the British had 38 hydrophone officers and 200 qualified listeners, paid an addition 4d per day. From late in World War I until the introduction of active sonar in the early 1920s, hydrophones were the sole method for submarines to detect targets while submerged. A small single cylindrical ceramic transducer can achieve near perfect omnidirectional reception. Directional hydrophones increase sensitivity from one direction using two basic techniques: This device uses a single transducer element with a dish or conical-shaped sound reflector to focus the signals, in a similar manner to a reflecting telescope; this type of hydrophone can be produced from a low-cost omnidirectional type, but must be used while stationary, as the reflector impedes its movement through water. A new way to direct is to use a spherical body around the hydrophone; the advantage of directivity spheres is that the hydrophone can be moved within the water, ridding it of the interferences produced by a conical-shaped element.
Multiple hydrophones can be arranged in an array so that it will add the signals from the desired direction while subtracting signals from other directions. The array may be steered using a beamformer. Most hydrophones are arranged in a "line array" but may be in two- or three-dimensional arrangements. SOSUS hydrophones, laid on the seabed and connected by underwater cables, were used, beginning in the 1950s, by the U. S. Navy to track movement of Soviet submarines during the Cold War along a line from Greenland and the United Kingdom known as the GIUK gap; these are capable of recording low frequency infrasound, including many unexplained ocean sounds. Communication with submarines Geophone Underwater acoustics Sonar Reflection seismology John. SOSUS. Retrieved January 28, 2005. Watlington, Frank. How to build & use low-cost hydrophones. Unknown. Hydrophone. Retrieved January 28, 2005. Unknown. Schlumberger Oilfield Glossary: Term'hydrophone'. Retrieved January 28, 2005. Onda Corporation.'Hydrophone Handbook'.
Report AIR 1/645/17/122/304 - National Archives Kew. Airship Hydrophone experiments. DOSITS—Hydrophone introduction at Discovery of Sound in the Sea orcasound.net—Live hydrophone streams from killer