Sensor

“ Sensor technologies are grouped into four areas: active, passive, imbedded, and processing.
Active sensors: By far, the most important of the energy-emitting sensors is radar. Among the best all-weather capabilities of any type of sensor, the role for and capabilities of radar have steadily increased since the Second World War. Radar systems are used for early warning, air defense, air asset management, air traffic control, naval fleet defense, detection and tracking of moving ground targets, missile targeting, missile terminal guidance, terrain data development, and weather prediction. ”

“ A sensor is a component that collects and delivers information about things in a specified area. By building a shared common platform such as IoT will create a richer ecosystem for all the people, by enabling the development of innovative systems to focus on the value-added of the human physical touch points of connected objects and the services that manage these objects [4] . ”

“ Our field study leader and Brazilian scientist, Joaõ, leads the way.
“I’ll take the carbon dioxide sensor,” Joaõ mentions. Then he picks up the sensor, a box-like device that is less than a foot long on its biggest dimension and weighs a few pounds. The climb to the tower top should take us only five minutes, but we stop about halfway up to listen to the sounds of birds and monkeys. Monkeys screech and howl. Like the birds, the monkeys keep their distance, and we rarely see one. ”

“ Sensor and manipulator technology is advancing apace, largely through rapid growth in the fields of industrial robotics and computer science. Approximately 40% of human sensory input is in the form of vision, so it is appropriate that most work in physical perception relates to visual information processing and remote scene nterpretation. Algorithms and specialized sensors developed for satellite on-board pattern recognition and scene analysis can enable the teleoperator to perform many of these functions. ”

“ Machine sensors and human eyes see entirely different things when minor changes in the world state occur. For instance, in hilly terrain at low sun angle, satellites sensor readings vary rapidly as the shadows progress, but most of what is of interest to human beings is invariant. ”

“ Hardware and software impervious to extreme pressure, temperature, and chemical conditions and with long lifespans are required. Also, a diverse assortment of onboard sensors with broad capabilities is necessary to produce basic information via complementary and selective sensing to be used in scientific investigation and planning. ”

“ A modular sensor is designed independently of a given pedal so that it can be taken off the shelf and attached to mechanical pedals of various sorts, enabling the pedals to be used in automobiles with computer-controlled throttles. ”

“ Manufacturers of electrochemical sensors are too numerous to list. For example, there are at least 16 companies that manufacture oxygen monitors with electrochemical sensors. Consult current publications in the field of industrial hygiene and safety for manufacturers of specific sensors [7,8] . ”

“ The traditional NASA information gathering philosophy has been to collect as much raw data as possible from each mission and then allow university, industrial, and government researchers to complete the analysis. In the early days of space exploration this strategy was reasonable, based on spacecraft investment, insofar as it maximized return. But today, advancing satellite technology has greatly expanded the number of sensors flown and available data rates. ”

“ A coherer or detector of electrical disturbances, Hertzian waves, light-waves, or other radiations, comprising a pair of galena contacts, pivoted conducting-arms carrying said contacts and insulated from each other except at the contacting point of said contacts, a spring tending to hold said contacts together, a micrometer-screw for adjusting the force of contact of said contacts, and means for insulating said arms from each other except at the point of contact of said contacting pieces and from external objects, substantially as described. ”

“ I fancy some of your radio experts would gape if they were permitted to see my wave meter. I believe it would cause some excitement in the laboratories of Lodge or Marconi. I—Proctor—I measured these waves which, of course, means that I found a detector for them. Our friend DeForest thinks that he has a monopoly on ultra-sensitive detectors. Proctor's detector is to the audion what a stop watch is to a wheel barrow! ”

“ FIG. 10.—A simple receiving arrangement. The detector rectifies the oscillatory currents passing from the aerial to the ground so that they will flow through the telephone receiver and register as sound.
The most prominent type of detector in use to-day is a crystal of silicon, iron pyrites, zincite or certain other minerals. The mineral is placed between two contact points, one or both of which are adjustable so that the most sensitive portion of the mineral may be selected. ”

“ The pulse-height analyzer is a device that sorts electrical impulses from the detector according to the energy of the gamma rays causing the impulses. The screen displays the gamma-ray spectrum and the electric typewriter automatically types out the data collected when the measurement is complete. ”

“ Current Detectors. As there is a magnetic field about a wire when a current passes through it, and as the magnetic needle is affected, we have a means of detecting the presence of a current. When the current is strong it is simply necessary to let it pass once over or under a needle; when it is weak, the wire must pass several times above and below the needle, Fig. 91, to give the needle motion. (See "Apparatus Book," Chapter XIII., for home-made detectors.)
[73]
Fig. ”

“ Each probe will have gravity instrumentation. Using the microwaves naturally occurring in space, they will be connected by a vast neural network and thus act as a single instrument, with all data being fed back to various information centers. ”

“ By following up this idea, also, we might go a little further. We might arrive at the conviction that our present science is human, petty, and contingent; that it is closely linked with the structure of our sensory organs; that this structure results from the evolution which fashioned these organs; that this evolution has been an accident of history; that in the future it may be different; ”

“ Another form of detector is the "electrolytic" which consists of a very fine platinum wire about one ten-thousandth of an inch in diameter, which dips into a platinum cup filled with nitric acid. When the invisible electro-magnetic waves impinge upon the wires of the receiving station, and cause electrical surges to take place in those wires, they in turn affect the detector, giving an exact reproduction of the note of the transmitting spark at the distant station. ”

“ After delivery of telemetry data on magnetic tapes by the DSIF, the CCF stored the data for later reduction and analysis. Where telemetry data were being processed in real or near-real time, certain critical engineering and scientific functions were programmed to print-out an “alarm” reading when selected measurements in the data were outside specified limits. ”

“ If by means of an electrometer we determine the electric potential at different points of a circuit in which a constant electric current is maintained, we shall find that in any portion of the circuit consisting of a single metal of uniform temperature throughout, the potential at any point exceeds that at any other point farther on in the direction of the current by a quantity depending on the strength of the current and on the nature and dimensions of the intervening portion of the circuit. ”

“ If the framework is substituted for the metal plate in the experiment on the reflection of electric waves, sparks will appear in the detector when the wires are parallel to the focal lines of the mirrors, and will disappear when the wires are at right angles to these lines. Thus the framework reflects but does not transmit the waves when the electric force in them is parallel to the wires, while it transmits but does not reflect waves in which the electric force is at right angles to the wires. ”

“ Sensorial perception, for example, certainly occurs with greater or less accuracy according to the degree of interest; it is constantly given other directions by the change of external stimuli and by ideas. ”

“ The light moves through one division on the scale, and the meter has started. I will ask you to observe its rate of vibration. I will now double the current; this is indicated by the light moving to the end of the second division on the scale: the meter vibrates twice as fast. Now the current is three times as strong, now four times, and so on. You will observe that the position of the spot of light and the rate of vibration always correspond. Every vibration of the meter corresponds to a definite quantity of electricity, and causes a hand on a dial to move on one step. ”

“ In order, however, that the apparatus to which this invention relates shall work to the best advantage, it is desirable that the distortion, whether positive or negative, produced by the light-wave or other radiation shall not only be readily detected and indicated, but also that the substance shall return to its normal state upon the cessation of the impressed radiation. For this reason it is desirable to use substances having a characteristic curve of the kind above referred to or to provide means whereby said substances shall be caused to give such characteristic curve. ”

“ The action of detectors, etc., depends upon this fact; and, strange to say, the magnetic field about the wire disappears the instant the current ceases to pass. The combination, thus, of a coil of wire and a magnetic needle, properly arranged, makes an instrument with which the presence of electricity can be detected. When the strength of a current is to be measured, or the strengths of two currents are to be compared, the apparatus is called a galvanometer. The method of making these pieces of apparatus will depend upon the strength of current to be tested or measured. ”

“ Time will not permit me to discuss all the different forms of electric-wave detector which have been invented. For our present purposes we must limit ourselves to the description of one plan, which depends on the remarkable fact that finely powdered dry metal or metallic filings are non-conductors of the electric current until they are subjected to an electromotive force exceeding a certain value, when the metallic filings at once pass into a conductive condition. ”

“ A fourth class of electric wave detector comprises the thermal detectors which operate in virtue of the fact that electric oscillations create heat in a fine wire through which they pass. One form such a detector takes is the bolometer. If a loop of very fine platinum wire, prepared by the Wollaston process, is included in an exhausted glass bulb like an incandescent lamp, then when electric oscillations are sent through it its resistance is increased. ”

“ Before, however, we can demonstrate this fact, we must have some means for detecting the [210] influence of what we call an electric wave. You will remember that, in the case of experiments with air waves, I used a sensitive flame in order to make evident to you the presence of waves in the air which you could not see, so here I must use an appropriate detector for electric waves, the operation of which will render evident to us the existence in the space round our electric oscillator of the electric waves we cannot see. ”

“ Although there may be no sharp and defined critical electromotive force, yet, nevertheless, as a matter of fact, if the electromotive force applied exceeds a certain value, then the detector passes suddenly from one state of conductivity to another. ”

“ External disturbances or stimuli impinging on a substance induce a molecular upset, the effectiveness of the stimulus depending on the rapidity of the onset of the disturbance. The molecular upset is attended by changes induced in the properties of the substance. The most sensitive means for its detection is electrical: by the method of conductivity or of electromotive variation (p. 170) .
Stimulation of the substance can be produced by electric radiation, by visible light, and by mechanical vibration. ”

“ If an electrified body is held near the gold-leaf electroscope the leaves diverge with electricity of the same sign as that of the body being tested. If, without removing the electrified body, the plate or knob of the electroscope is touched, the leaves collapse. If the electroscope is insulated once more and the electrified body removed, the leaves again diverge with electricity of the opposite sign to that of the body being tested. The sign of charge is then determined by holding near the electroscope a glass rod rubbed with silk or a sealing-wax rod rubbed with flannel. ”

“ Five of the remote sensing instruments—the two TV cameras, the infrared spectrometer, the ultraviolet spectrometer, and the photopolarimeter—are mounted together on a scan platform. This platform can be pointed to almost any direction in space, allowing exact targeting of the observations. ”

“ I used six wires forming three metallic circuits and influencing three needles. I worked out every possible permutation and practical combination of the signals given by the three needles, and I thus obtained an alphabet of twenty-six signals. I had invented the instrument which I called the detector; by means of which injuries to the wires, whether from water, fracture, or contact, are readily traced; an instrument which, in practice, is never out of my hand, and without which the electric telegraph would be impracticable. ”