Mass flow sensor
A mass flow sensor is a sensor used to determine the mass flow rate of air entering a fuel-injected internal combustion engine. The air mass information is necessary for the engine control unit to balance and deliver the correct fuel mass to the engine. Air changes its density with pressure. In automotive applications, air density varies with the ambient temperature and the use of forced induction, which means that mass flow sensors are more appropriate than volumetric flow sensors for determining the quantity of intake air in each cylinder. There are two common types of mass airflow sensors in use on automotive engines; these are the hot wire. Neither design employs technology. However, with additional sensors and inputs, an engine's ECU can determine the mass flow rate of intake air. Both approaches are used exclusively on electronic fuel injection engines. Both sensor designs output a 0.0–5.0 volt or a pulse-width modulation signal, proportional to the air mass flow rate, both sensors have an intake air temperature sensor incorporated into their housings for most post on-board diagnostics vehicles.
Vehicles prior to 1996 could have MAF without an IAT. An example is 1994 Infiniti Q45; when a MAF sensor is used in conjunction with an oxygen sensor, the engine's air/fuel ratio can be controlled accurately. The MAF sensor provides the open-loop controller predicted air flow information to the ECU, the oxygen sensor provides closed-loop feedback in order to make minor corrections to the predicted air mass. See manifold absolute pressure sensor; the VAF sensor measures the air flow into the engine with a spring-loaded air vane attached to a variable resistor. The vane moves in proportion to the airflow. A voltage is applied to the potentiometer and a proportional voltage appears on the output terminal of the potentiometer in proportion to the angle the vane rotates, or the movement of the vane may directly regulate the amount of fuel injected, as in the K-Jetronic system. Many VAF sensors have an air-fuel adjustment screw, which opens or closes a small air passage on the side of the VAF sensor.
This screw controls the air-fuel mixture by letting a metered amount of air flow past the air flap, thereby leaning or richening the mixture. By turning the screw clockwise the mixture is counterclockwise the mixture is leaned; the vane moves because of the drag force of the air flow against it. The drag force depends on air velocity and the shape of the vane, see drag equation; some VAF sensors include an additional intake air temperature sensor to allow the engines ECU to calculate the density of the air, the fuel delivery accordingly. The vane meter approach has some drawbacks: it restricts airflow which limits engine output its moving electrical or mechanical contacts can wear finding a suitable mounting location within a confined engine compartment is problematic the vane has to be oriented with respect to gravity. In some manufacturers fuel pump control was part on the VAF internal wiring. A hot wire mass airflow sensor determines the mass of air flowing into the engine’s air intake system.
The theory of operation of the hot wire mass airflow sensor is similar to that of the hot wire anemometer. This is achieved by heating a wire suspended in the engine’s air stream, like a toaster wire, with either a constant voltage over the wire or a constant current through the wire; the wire's electrical resistance increases as the wire’s temperature increases, which varies the electrical current flowing through the circuit, according to Ohm's law. When air flows past the wire, the wire cools, decreasing its resistance, which in turn allows more current to flow through the circuit, since the supply voltage is a constant; as more current flows, the wire’s temperature increases until the resistance reaches equilibrium again. The current increase or decrease is proportional to the mass of air flowing past the wire; the integrated electronic circuit converts the proportional measurement into a calibrated signal, sent to the ECU. If air density increases due to pressure increase or temperature drop, but the air volume remains constant, the denser air will remove more heat from the wire indicating a higher mass airflow.
Unlike the vane meter's paddle sensing element, the hot wire responds directly to air density. This sensor's capabilities are well suited to support the gasoline combustion process which fundamentally responds to air mass, not air volume; this sensor sometimes employs a mixture screw, but this screw is electronic and uses a variable resistor instead of an air bypass screw. The screw needs more turns to achieve the desired results. A hot wire burn-off cleaning circuit is employed on some of these sensors. A burn-off relay applies a high current through the platinum hot wire after the vehicle is turned off for a second or so, thereby burning or vaporizing any contaminants that have stuck to the platinum hot wire element; the hot film MAF sensor works somewhat similar to the hot wire MAF sensor, but instead it outputs a frequency signal. This sensor uses a hot film-grid instead of a hot wire, it is found in late 80’s early 90’s fuel-injected vehicles. The output frequency is directly proportional to the air mass entering the engine.
So as mass flow increases so does frequency. These sensors tend to cause intermittent problems due to internal electrical failures; the use of an oscilloscope is recommended to check the outp
A speedometer or a speed meter is a gauge that measures and displays the instantaneous speed of a vehicle. Now universally fitted to motor vehicles, they started to be available as options in the 1900s, as standard equipment from about 1910 onwards. Speedometers for other vehicles use other means of sensing speed. For a boat, this is a pit log. For an aircraft, this is an airspeed indicator. Charles Babbage is credited with creating an early type of a speedometer, fitted to locomotives; the electric speedometer was invented by the Croatian Josip Belušić in 1888 and was called a velocimeter. Patented by Otto Schultze on 7 October 1902, it uses a rotating flexible cable driven by gearing linked to the output of the vehicle's transmission; the early Volkswagen Beetle and many motorcycles, use a cable driven from a front wheel. When the vehicle is in motion, a speedometer gear assembly turns a speedometer cable, which turns the speedometer mechanism itself. A small permanent magnet affixed to the speedometer cable interacts with a small aluminum cup attached to the shaft of the pointer on the analogue speedometer instrument.
As the magnet rotates near the cup, the changing magnetic field produces eddy currents in the cup, which themselves produce another magnetic field. The effect is that the magnet exerts a torque on the cup, "dragging" it, thus the speedometer pointer, in the direction of its rotation with no mechanical connection between them; the pointer shaft is held toward zero by a fine torsion spring. The torque on the cup increases with the speed of rotation of the magnet, thus an increase in the speed of the car will twist the cup and speedometer pointer against the spring. The cup and pointer will turn until the torque of the eddy currents on the cup are balanced by the opposing torque of the spring, stop. Given the torque on the cup is proportional to the car's speed, the spring's deflection is proportional to the torque, the angle of the pointer is proportional to the speed, so that spaced markers on the dial can be used for gaps in speed. At a given speed, the pointer will remain motionless and pointing to the appropriate number on the speedometer's dial.
The return spring is calibrated such that a given revolution speed of the cable corresponds to a specific speed indication on the speedometer. This calibration must take into account several factors, including ratios of the tailshaft gears that drive the flexible cable, the final drive ratio in the differential, the diameter of the driven tires. One of the key disadvantages of the eddy current speedometer is that it cannot show the vehicle speed when running in reverse gear since the cup would turn in the opposite direction - in this scenario the needle would be driven against its mechanical stop pin on the zero position. Many modern speedometers are electronic. In designs derived from earlier eddy-current models, a rotation sensor mounted in the transmission delivers a series of electronic pulses whose frequency corresponds to the rotational speed of the driveshaft, therefore the vehicle's speed, assuming the wheels have full traction; the sensor is a set of one or more magnets mounted on the output shaft or differential crownwheel, or a toothed metal disk positioned between a magnet and a magnetic field sensor.
As the part in question turns, the magnets or teeth pass beneath the sensor, each time producing a pulse in the sensor as they affect the strength of the magnetic field it is measuring. Alternatively,particularly in vehicles with multiplex wiring, some manufacturers use the pulses coming from the ABS wheel sensors which communicate to the instrument panel via the CAN Bus. Most modern electronic speedometers have the additional ability over the eddy current type to show the vehicle speed when moving in reverse gear. A computer converts the pulses to a speed and displays this speed on an electronically controlled, analog-style needle or a digital display. Pulse information is used for a variety of other purposes by the ECU or full-vehicle control system, e.g. triggering ABS or traction control, calculating average trip speed, or to increment the odometer in place of it being turned directly by the speedometer cable. Another early form of electronic speedometer relies upon the interaction between a precision watch mechanism and a mechanical pulsator driven by the car's wheel or transmission.
The watch mechanism endeavors to push the speedometer pointer toward zero, while the vehicle-driven pulsator tries to push it toward infinity. The position of the speedometer pointer reflects the relative magnitudes of the outputs of the two mechanisms. Typical bicycle speedometers measure the time between each wheel revolution, give a readout on a small, handlebar-mounted digital display; the sensor is mounted on the bike at a fixed location, pulsing when the spoke-mounted magnet passes by. In this way, it is analogous to an electronic car speedometer using pulses from an ABS sensor, but with a much cruder time/distance resolution - one pulse/display update per revolution, or as as once every 2–3 seconds at low speed with a 26-inch wheel. However, this is a critical problem, the system provides frequent updates at higher road speeds where the information is of more importance; the low pulse frequency has little impact on measurement accuracy, as these digital devices can be programmed by wheel size, or additionally by wheel or tire circumference in order to make distance measurements more accurate and precise than a typical motor vehicle gauge.
However these devices carry some minor disadvantage in requiring power from batteries that must be replaced every so in the rec
Research Triangle Park
The Research Triangle Park is the largest research park in the United States. It is named for the three hub cities of Raleigh and Chapel Hill, or more properly for the three major research universities in those three cities; the Research Triangle region of North Carolina received its name as an extension of the name of the park. Besides the three anchor cities, the park is bounded by the communities of Morrisville and Cary. One fourth of the park's territory lies in Wake County, but the majority of its land is in Durham County. RTP is one of the most prominent high-tech development parks in the United States, it was created in 1959 by state and local governments, nearby universities, local business interests. Karl Robbins bought the land; the park covers 7,000 acres situated in a pine forest with 22,500,000 square feet of built space. The park is traversed by Interstate 40; the park is home to over 200 companies employing 50,000 workers and 10,000 contractors, including the second largest IBM operation in the world, smaller only than the one in India.
The park hosts one of GlaxoSmithKline's largest R&D centers with 5,000 employees. Cisco Systems' campus in RTP, with 5,000 employees, is the second highest concentration of its employees outside of its Silicon Valley corporate headquarters; the National Institute of Health has its National Institute of Environmental Health Sciences located in RTP and Durham. Research Triangle Park is owned and managed by the Research Triangle Foundation, a private non-profit organization. In August 2017, Scott Levitan was named the organization's new President and CEO, making him the 9th leader since the foundation was established. Following World War II, North Carolina's economy could no longer depend upon their traditional industries of agriculture and furniture. Academics at N. C. State and Duke came up with the idea of creating the park so that the universities could do research together, leverage the area's strengths, keep graduates in state. Established in 1951 and located in North Carolina, Research Triangle Park was created to increase innovation in the area.
It is near Duke University, North Carolina State University, the University of North Carolina at Chapel Hill. At first, the park struggled to recruit innovators, but in 1965, Research Triangle Park had its largest surge of growth, thanks to heavy recruiting by the state's government and Archibald Davis. In their article "The Growth of Research Triangle Park," Link and Scott posit that entrepreneurial culture and leadership contributed the most to its success as a cluster. Archie Davis promoted a culture of innovation and entrepreneurship by locating the park near universities recruiting organizations, used his vision to raise funding for the park. Davis believed that profits could not be the only driver for creating the park - the betterment of the community should be the key goal. "The love of this state … was the motivation for the Research Triangle idea," he said. "Research Triangle is a manifestation of what North Carolina is all about." Research Triangle Park remains a nonprofit. The park is an unincorporated area, state law prohibits municipalities from annexing areas within the park.
Some local government functions are served by the Durham-Wake Counties Research and Production Service District, a special tax district created in 1986, conterminous with the park, wherein the property tax rate is limited to 10 cents per $100 valuation. The park has special zoning as a Research Applications District in the Wake County portion, a Scientific Research Park in the Durham County portion; as of October 2012, both zoning areas are in the process of being revised to allow higher density development. The zoning changes are coupled with legislative changes allowing for Urban Research Service Districts within the Park, which can include a mix of retail and residential usages; these newly permitted. On October 1, 2015, former President and CEO of the Research Triangle Foundation, Bob Geolas, announced RTP's plans for a $50 million redevelopment involving the formation of "Park Center." $20 million will be allocated from Durham County, $10 million from the Durham-Wake Counties Research and Production Service District, $20 million as a result of land purchases and site work provided by the Research Triangle Foundation of North Carolina.
Park Center is to be over 300,000 square feet of public space at the heart of the Research Triangle Park. This public area will include retail outlets and beverage venues, entertainment space. Geolas states. I would like to have as no chains if we could. I'd love for it. Local coffee, local food, local produce, local products."The redevelopment plans include exploring partnerships with regional transit groups. The hope of the Research Triangle Foundation is to broaden public transportation to and from the area. According to Geolas, "We are having discussions about bringing the Regional Transit Center over to Park Center so that we can connect with all of our transit links." A public commuter rail is in talks. The Research Triangle Park Foundation operates three buildings within RTP; these three buildings are The Frontier, The Lab, The Archie K. Davis Conference Center; the Frontier is a co
In mathematics, the trigonometric functions are functions of an angle. They relate the angles of a triangle to the lengths of its sides. Trigonometric functions are important in the study of triangles and modeling periodic phenomena, among many other applications; the most familiar trigonometric functions are the sine and tangent. In the context of the standard unit circle, where a triangle is formed by a ray starting at the origin and making some angle with the x-axis, the sine of the angle gives the y-component of the triangle, the cosine gives the x-component, the tangent function gives the slope. For angles less than a right angle, trigonometric functions are defined as ratios of two sides of a right triangle containing the angle, their values can be found in the lengths of various line segments around a unit circle. Modern definitions express trigonometric functions as infinite series or as solutions of certain differential equations, allowing the extension of the arguments to the whole number line and to the complex numbers.
Trigonometric functions have a wide range of uses including computing unknown lengths and angles in triangles. In this use, trigonometric functions are used, for instance, in navigation and physics. A common use in elementary physics is resolving a vector into Cartesian coordinates; the sine and cosine functions are commonly used to model periodic function phenomena such as sound and light waves, the position and velocity of harmonic oscillators, sunlight intensity and day length, average temperature variations through the year. In modern usage, there are six basic trigonometric functions, tabulated here with equations that relate them to one another. With the last four, these relations are taken as the definitions of those functions, but one can define them well geometrically, or by other means, derive these relations; the notion that there should be some standard correspondence between the lengths of the sides of a triangle and the angles of the triangle comes as soon as one recognizes that similar triangles maintain the same ratios between their sides.
That is, for any similar triangle the ratio of the hypotenuse and another of the sides remains the same. If the hypotenuse is twice as long, so are the sides, it is these ratios. To define the trigonometric functions for the angle A, start with any right triangle that contains the angle A; the three sides of the triangle are named as follows: The hypotenuse is the side opposite the right angle, in this case side h. The hypotenuse is always the longest side of a right-angled triangle; the opposite side is the side opposite in this case side a. The adjacent side is the side having both the angles in this case side b. In ordinary Euclidean geometry, according to the triangle postulate, the inside angles of every triangle total 180°. Therefore, in a right-angled triangle, the two non-right angles total 90°, so each of these angles must be in the range of as expressed in interval notation; the following definitions apply to angles in this range. They can be extended to the full set of real arguments by using the unit circle, or by requiring certain symmetries and that they be periodic functions.
For example, the figure shows sin for angles θ, π − θ, π + θ, 2π − θ depicted on the unit circle and as a graph. The value of the sine repeats itself apart from sign in all four quadrants, if the range of θ is extended to additional rotations, this behavior repeats periodically with a period 2π; the trigonometric functions are summarized in the following table and described in more detail below. The angle θ is the angle between the hypotenuse and the adjacent line – the angle at A in the accompanying diagram; the sine of an angle is the ratio of the length of the opposite side to the length of the hypotenuse. The word comes from the Latin sinus for gulf or bay, given a unit circle, it is the side of the triangle on which the angle opens. In that case: sin A = opposite hypotenuse The cosine of an angle is the ratio of the length of the adjacent side to the length of the hypotenuse, so called because it is the sine of the complementary or co-angle, the other non-right angle; because the angle sum of a triangle is π radians, the co-angle B is equal to π/2 − A.
In that case: cos A = adjacent hypotenuse The tangent of an angle is the ratio of the length of the opposite side to the length of the adjacent side, so called because it can be represented as a line segment tangent to the circle, i.e. the line that touches the circle, from Latin linea tangens or touching line. In our case: tan A = opposite adjacent Tangent may be represented in terms of sine and cosine; that is: tan A = sin A cos A = opposite
Heat flux sensor
A heat flux sensor is a transducer that generates an electrical signal proportional to the total heat rate applied to the surface of the sensor. The measured heat rate is divided by the surface area of the sensor to determine the heat flux; the heat flux can have different origins. Heat flux sensors are known under different names, such as heat flux transducers, heat flux gauges, heat flux plates; some instruments that are single-purpose heat flux sensors like pyranometers for solar radiation measurement. Other heat flux sensors include Gardon gauges, thin-film thermopiles, Schmidt-Boelter gauges. In SI units, the heat rate is measured in Watts, the heat flux is computed in Watts per meter squared. Heat flux sensors are used for a variety of applications. Common applications are studies of building envelope thermal resistance, studies of the effect of fire and flames or laser power measurements. More exotic applications include estimation of fouling on boiler surfaces, temperature measurement of moving foil material, etc.
The total heat flux is composed of a conductive and radiative part. Depending on the application, one might want to measure all three of these quantities or single one out. An example of measurement of conductive heat flux is a heat flux plate incorporated into a wall. An example of measurement of radiative heat flux density is a pyranometer for measurement of solar radiation. An example of a sensor sensitive to radiative as well as convective heat flux is a Gardon or Schmidt–Boelter gauge, used for studies of fire and flames; the Gardon must measure convection perpendicular to the face of the sensor to be accurate due to the circular-foil construction, while the wire-wound geometry of the Schmidt-Boelter gauge can measure both perpendicular and parallel flows. In this case the sensor is mounted on a water-cooled body; such sensors are used in fire resistance testing to put the fire to which samples are exposed to the right intensity level. There are various examples of sensors that internally use heat flux sensors examples are laser power meters, etc.
We will discuss three large fields of application in. Soil heat flux is a most important parameter in agro-meteorological studies, since it allows one to study the amount of energy stored in the soil as a function of time. Two or three sensors are buried in the ground around a meteorological station at a depth of around 4 cm below the surface; the problems that are encountered in soil are threefold: First is the fact that the thermal properties of the soil are changing by absorption and subsequent evaporation of water. Second, the flow of water through the soil represents a flow of energy, going together with a thermal shock, misinterpreted by conventional sensors; the third aspect of soil is that by the constant process of wetting and drying and by the animals living on the soil, the quality of the contact between sensor and soil is not known. The result of all this is the quality of the data in soil heat flux measurement is not under control. In a world more concerned with saving energy, studying the thermal properties of buildings has become a growing field of interest.
One of the starting points in these studies is the mounting of heat flux sensors on walls in existing buildings or structures built for this type of research. Heat flux sensors mounted to building walls or envelope component can monitor the amount of heat energy loss/gain through that component and/or can be used to measure the envelope thermal resistance, R-value, or thermal transmittance, U-value; the measurement of heat flux in walls is comparable to that in soil in many respects. Two major differences however are the fact that the thermal properties of a wall do not change and that it is not always possible to insert the heat flux sensor in the wall, so that it has to be mounted on its inner or outer surface; when the heat flux sensor has to be mounted on the surface of the wall, one has to take care that the added thermal resistance is not too large. The spectral properties should be matching those of the wall as as possible. If the sensor is exposed to solar radiation, this is important.
In this case one should consider painting the sensor in the same color as the wall. In walls the use of self-calibrating heat flux sensors should be considered; the measurement of the heat exchange of human beings is of importance for medical studies, when designing clothing, immersion suits and sleeping bags. A difficulty during this measurement is that the human skin is not suitable for the mounting of heat flux sensors; the sensor has to be thin: the skin is a constant temperature heat sink, so added thermal resistance has to be avoided. Another problem is; the contact between the test person and the sensor can be lost. For this reason, whenever a high level of quality assurance of the measurement is required, it can be recommended to use a self-calibrating sensor. Heat flux sensors are used in industrial environments, where temperature and heat flux may be much higher. Examples of these environments are aluminium smelting, solar concentrators, coal fired boilers, blast furnaces, flare systems, fluidized beds, cokers...
A heat flux sensor should measure the local heat flux density in one direction. The result is expressed in watts per square meter; the calculation is done according to: ϕ q = V s e n
An electronic nose is a device intended to detect odors or flavors. Over the last decades, "electronic sensing" or "e-sensing" technologies have undergone important developments from a technical and commercial point of view; the expression "electronic sensing" refers to the capability of reproducing human senses using sensor arrays and pattern recognition systems. Since 1982, research has been conducted to develop technologies referred to as electronic noses, that could detect and recognize odors and flavors; the stages of the recognition process are similar to human olfaction and are performed for identification, comparison and other applications, including data storage and retrieval. However, hedonic evaluation is a specificity of the human nose given that it is related to subjective opinions; these devices are now used to fulfill industrial needs. In all industries, odor assessment is performed by human sensory analysis, by chemosensors, or by gas chromatography; the latter technique gives information about volatile organic compounds but the correlation between analytical results and meme odor perception is not direct due to potential interactions between several odorous components.
In the Wasp Hound odor detector, the mechanical element is a video camera and the biological element is five parasitic wasps who have been conditioned to swarm in response to the presence of a specific chemical. Scientist Alexander Graham Bell popularized the notion that it was difficult to measure a smell, in 1914 said the following: Did you measure a smell? Can you tell whether one smell is just twice strong as another? Can you measure the difference between two kinds of smell and another? It is obvious that we have many different kinds of smells, all the way from the odour of violets and roses up to asafetida, but until you can measure their likeness and differences, you can have no science of odour. If you are ambitious to find a new science, measure a smell. In the decades since Bell made this observation, no such science of odor materialised, it was not until the 1950s and beyond that any real progress was made; the electronic nose was developed in order to mimic human olfaction that functions as a non-separative mechanism: i.e. an odor / flavor is perceived as a global fingerprint.
The instrument consists of head space sampling, sensor array, pattern recognition modules, to generate signal pattern that are used for characterizing odors. Electronic noses include three major parts: a sample delivery system, a detection system, a computing system; the sample delivery system enables the generation of the headspace of a sample, the fraction analyzed. The system injects this headspace into the detection system of the electronic nose; the sample delivery system is essential to guarantee constant operating conditions. The detection system, which consists of a sensor set, is the "reactive" part of the instrument; when in contact with volatile compounds, the sensors react, which means they experience a change of electrical properties. In most electronic noses, each sensor is sensitive to all volatile molecules but each in their specific way. However, in bio-electronic noses, receptor proteins which respond to specific odor molecules are used. Most electronic noses use sensor arrays that react to volatile compounds on contact: the adsorption of volatile compounds on the sensor surface causes a physical change of the sensor.
A specific response is recorded by the electronic interface transforming the signal into a digital value. Recorded data are computed based on statistical models. Bio-electronic noses use olfactory receptors - proteins cloned from biological organisms, e.g. humans, that bind to specific odor molecules. One group has developed a bio-electronic nose that mimics the signaling systems used by the human nose to perceive odors at a high sensitivity: femtomolar concentrations; the more used sensors for electronic noses include metal–oxide–semiconductor devices - a transistor used for amplifying or switching electronic signals. This works on the principle that molecules entering the sensor area will be charged either positively or negatively, which should have a direct effect on the electric field inside the MOSFET. Thus, introducing each additional charged particle will directly affect the transistor in a unique way, producing a change in the MOSFET signal that can be interpreted by pattern recognition computer systems.
So each detectable molecule will have its own unique signal for a computer system to interpret. Conducting polymers - organic polymers that conduct electricity. Polymer composites - similar in use to conducting polymers but formulated of non-conducting polymers with the addition of conducting material such as carbon black. Quartz crystal microbalance - a way of measuring mass per unit area by measuring the change in frequency of a quartz crystal resonator; this can be used for future reference. Surface acoustic wave - a class of microelectromechanical systems which rely on the modulation of surface acoustic waves to sense a physical phenomenon; some devices combine multiple sensor types in a single device, for example polymer coated QCMs. The independent information leads to efficient devices. In recent years, other types of electronic noses have been developed that utilize mass spectrometry or ultra-fast gas chromatography as a detection system; the computing system works to combine the responses of all of the sensors, which represents the input for the data treatment.
This part of the instrument performs global fingerprint analysis and provides results and representations that can be interpreted. Moreover, the electronic nose r
A defect detector is a device used on railroads to detect axle and signal problems in passing trains. The detectors are integrated into the tracks and include sensors to detect several different kinds of problems that could occur. Defect detectors were one invention which enabled American railroads to eliminate the caboose at the rear of the train, as well as various station agents stationed along the route to detect unsafe conditions; the use of defect detectors has since spread to other overseas railroads. Before the advent of automated detectors, on-board train crew and track-side workers used to visually inspect trains for defects e.g. "hotboxes" would smoke or glow red. By the 1940s, automatic defect detectors included infrared sensors for hotboxes, wires outlining the clearance envelope to detect high and wide loads, "brittle bars" – frangible bars mounted between the rails – to detect dragging equipment; the detectors would transmit their data via wired links to remote read-outs in stations, offices or interlocking towers, where a stylus-and-cylinder gauge would record a reading for every axle.
The first computerized detectors had lights indicating the nature of defect and a numeric display of the associated axle number. Seaboard Air Line was the first railroad to install defect detectors which "spoke" their results over radios carried by train crew. Models allowed crews to interact with the detector using a touch tone function on their radios to recall the defect report. Today, defect detectors are part of the general monitoring platforms keeping track of train status. A Defect Detector Would Sound Like This: CSX Equipment Defect Detector Milepost 484.6 No Defects Repeat No Defects. Total Axle 721. Train Length 12,973. Track 1. Temperature 63. End Of Transmission; the sensors installed at defect detector locations can include and are explained: Hot boxes or Hot Bearing Detectors are used to measure the temperature of the journal bearings of a train. They consist of two infrared eyes on each side of the tracks looking up at the train's bearings, they register the radiation from every journal.
If a bearing reaches the maximum temperature for safe travel, the detector will flag and count it as a defect. A column of cones sits across the whole width of the railroad attached to a switch. Anything dragging from the train will hit this cone, it returns to its normal position to prepare for anything else that might be dragging under the train. The detector will register this flag it as a defect. Brittle bars are still used elsewhere, but still have to be repaired. Over time, dragging equipment detector's metal flaps need to be replaced because of extensive damage to them. Single use systems involve a frangible engagement bar or a stainless steel wire/braid strung between the rails and outside the rails as well, fastened to the sleepers. If the bar or braid is hit by something it breaks, the circuit break alerts that there is a dragging item. Auto-resetting systems involve a pivot pin system to allow the target to reset itself after a hit. Infrared beams are placed horizontally above the track or vertically next to the track.
Anything that breaks the beam will be counted as a defect. A high car detector is placed anywhere an excess height car could be routed onto a low clearance line. A shifted load detector is found on railroads where double-stack trains are prevalent as the containers may become misaligned and present a hazard to bridge trusses or tunnel walls. Wheel sensors along the tracks feel for flat spots on the train's wheels. Any flat wheel that becomes too dangerous to travel on will be counted as a defect; these systems utilize accelerometers, strain gauges, fiber optic methods, or the latest wheel impact phase detector. A wheel impact load detector measures impacts, but does not normalize these impact measurements against anything: the impact reading, they do not attempt to cater for differences in sprung mass, as they are measuring wheel defect impact rather than impact load. Therefore, the same wheel defect will register a much larger impact when a wagon is loaded, versus when it is empty. A wheel condition monitoring detector monitors the condition of the wheel independent of sprung mass – independent of load.
They do this by subtracting the wheel mass to get the normalized impact value. These systems are therefore better at detecting smaller defects with greater resolution. A length of side looking infrared detectors that can detect if a wheel has locked up and is sliding along the track or has had the brakes lock up causing the entire wheel to heat up; these detectors are a crude weighbridge and/or WILD system, as they are only concerned with measuring weight differentials. They do not have to be as accurate as proper weighbridge or WILD systems, but just accurate enough to be able to average the weight of bogies during a train pass to calculate the relative balance of wagons, to establish if one rail is loaded unacceptably greater than the other; this is not performed on empty wagons because of the significant percentage imbalances that can be caused by fluctuations in weight due to bogie tracking geometry or hunting issues, which in terms of weight differentials are accentuated compared to when a wagon is loaded.
These detectors can use a variety of sensors, but they are a safety curta