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ELEKTOR ELECTRONtCS JANUARY THE COMPLETE PREAMPLIFIER (I) mK1 (Record selec!) Cireui! diagram 01!he busboardELEKTOR ELECTRONICS JANUARY .. Audio dSP for diY applications – Home | Elektor elektor 49 Review: Elektor (febrero )Devices & Hardware. Revista Española Elektor 8 (Enero ) by elmar_quiceno. Elmar Duque Quiceno · Elektor 9 (Febrero ).pdf. Uploaded by. Elmar Duque Quiceno · Elektor 3. Uploaded by. Elmar Duque UControl 08 (Año 3-En ).pdf. Uploaded by. Infra-red becomes betterunderstoodIn , the Austrian physicist JosefGENERALINTEREST14 Elektor Electronics /Light that.

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Home Documents Elektor Us Post on Feb 34 views. Infra-red is radiation ofthe second kind, noticeable by its heatingeffect. All three types share four characteristics. To begin with they can be transmittedthrough space; secondly they can berefracted; thirdly they can be reflected andfinally they are obstructed by a black surface. This last explains for example why thephotographic plate is a negative.

William HerschelIn the astronomer William Herschelspaper An investigation of the powers of prismaticcolours to heat and illuminate objects outlined hisdiscovery of Infra-red radiation. He had beenconducting an experiment to discover theheating power of different parts of the spec-trum. He had begun by passing sunlight througha prism with thermometers set up on thetable beyond the red end of the spectrum, 1his aim being to determine if some of thecolours in his spectrum gave out more heatthan others.

His apparatus is illustrated inFigure 1. As he moved towards the red end of theelectromagnetic spectrum, he noted that histhermometers registered a rise in tempera-ture. Herschel then moved the thermometerpast the red end of the spectrum so as to notewhere, exactly, the heating effect disap-peared. However, exactly the reverse happened,the temperature rising higher still.

Conse-quently the region came to be known as theInfra-red, or Beyond the red, Infra being the Latinword for below.

Simply because red light con-tains less energy than any other form of visi-ble light and, in terms of energy content, is atthe bottom rung. Infra-red, having even lessenergy, is below 20010. Infra-red wavelengthsThe infra-red wavelengths extendfrom ffbrero limit of the visible spec-trum, known as the Near Region, tothe shortest microwaves, or the FarRegion, as illustrated in Figure 2.

Formerly, light wavelengths weremeasured in ngstrom units, afterthe Swedish physicist andastronomer Anders Jns ngstrom,a pioneer of spectroscopy.

Figure 2 illustrates the wave-lengths of the various colours in thelight spectrum in both ngstromunits and nano-metres where onenmetre is equal to fbrero whichhave largely superseded them.

Redlight is refracted fberero least; orange,yellow, green and blue are refractedin increasing amounts whilst violetis the colour refracted to the great-est extent.

Having discovered the phenome-non, Herschel was at something of aloss when it came to interpretingwhat hed found. Initial impressionsamong the scientific communitywere that the sun apparently emitted heat rays as well as lightrays, the former being refracted to alesser degree than the latter.

Macedonio MelloniSome fifty years after Herschelspaper was published, the Elekor Macedonio Melloni beganto answer many of the questionsrelating to infra-red radiation.

In, he had already measured theheating effect of the suns light,reflected from the moon at night. Melloni was also the inventor ofthe Thermopile, a series of strips ofdifferent metals he used blocks ofbismuth and antimony that pro-duced electric currents when oneend was heated.

This deviceenabled physicists to detect not onlyvery weak electric currents, but alsovery weak heating effects. InMelloni used his inven-tion to detect Herschels infra-redradiation every bit as delicately asthe human eye can detect light. Heshortly demonstrated that infra-reddisplayed all the properties ofwhite light such as interferenceand polarisation. Therefore infra-red was a wave phenomenon, justas light was, but with this differ-ence: Yet if we had the capacity touse infra-red light, there would be nodarkness for us.

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Even on the black-est nights, every object would bevisible, lit by a radiance as great asthat provided by a full moon, butwith a weird difference. There wouldbe no shadows on the ground,because earth itself would be theprincipal source of light. Herschels apparatus fordetermining the heating effect of thesolar spectrum.

Nicholson toohad a distinguished career in planetary sci-ence, becoming the discoverer of the ninth,tenth and eleventh moons of Jupiter.

Theseobservations were possible of course becausethe infra-red range of the spectrum is sosensitive that it can detect objects whosetemperatures are only a few degrees aboveabsolute zero. Meteorologists the world over wereecstatic.

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For the first time, the peoples of theEarth could see just how accurate the earlyexplorers and mapmakers had been, in theirportrayal of elejtor planets major landmassesand seas. Seven years later two American scientists,F. Kleinmann, began a searchfor galaxies emitting energy at infra-redwavelengths and in the following year twomore American researchers, Eric Becklin andGerry Neugebauer, reported their observa-tions of the galactic centre at infra-red fre-quencies.

ByLow and Kleinmann hadreported a number of galaxies emitting in theinfra-red band, and Neugebauer and febrefo col-league Robert Leighton had completed theirsurvey of the sky at the relatively short infra-red wavelength of 2.

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Carrying a cmreflecting telescope which along with theinfra-red detectors was cooled to 2 K byliquid helium, this vehicle was a jointendeavour by the United States, the Nether-lands and Great Britain. Ithad a total of 62 detectors, 15 or 16 beingused for each of the four infra-red wave-lengths.

The same segment of the sky wasobserved by at least two of the detectors, andso a true reading was one that had beenregistered by both detectors. During its 10 months of operation it per-Stefan whod been studying thenature of hot bodies, particularlytheir method of cooling demon-strated that a bodys total radiationwas proportional to the fourth powerof its temperature. This came to becalled Stefans Law. Five years later, Stefans formerlaboratory assistant, Ludwig Boltz-mann, showed that Stefans Lawcould be proven from first principlesand so it came to be called the Ste-fan-Boltzmann Law.

If, for example,a bodys temperature tripled from1, to 3, K, its radiant outputwould increase by 3x3x3x3, or 81times.

This meant that no matterhow cold a radiating source was, itcould still be detected because,when studied at infra-red, it wouldseem as bright as if its temperaturewere multiplied by itself four times! This of course was a very speedyrise indeed, one which surprised thescientific community of the day.

Nev-ertheless the law was soon put tothe test, as a technique for estab-lishing the surface temperature ofthe sun. This turned out to be around5, K. Another early application of infra-red was in photography. In William Abney, the renowned Britishphotographic scientist and discov-erer of the Abney Effect, developedtechniques for detecting infra-redradiation with photographs andused them to observe the suns spec-trum, far into this particular area ofthe solar spectrum.

Inthe Americanastronomer-physicist WilliamCoblentz became Chief of theRadiometry Section ofthe National Bureau ofStandards, a post hedretain for the next 40years. With his col-leagues Edison Pettitand Seth BarnesNicholson, he concen-trated primarily oninfra-red spec-troscopy. Throughoutthe s, they car-ried out the first sys-tematic infra-redobservations of stellarobjects, among whichwere not only starsand planets, but alsogas clouds and nebu-lae.

The electromagnetic spectrum, illustrating the location of the infra-redregion. It also discovered evidence ofplanet formation around stars outside thesolar system before as expected the liq-uid helium coolant ran out, in November In all, this remarkable satellite recorded some, objects, among which was the aster-oid Phaethon, the source of the Geminidmeteorite shower. This was the first suchbody to be discovered by a space craft.

This IRAS discovery was later stud-ied by a team of American and Britishastronomers, using ground-based optical tele-scopes. It proved to be an astonishing 16,million light years away from us! Another discovery was the existence ofextremely cold clouds of hydrocarbons which astronomers termed infra-red cirrus in interstellar space.

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Moreover, infra-red radi-ation from these gas and dust cloudsbetween stars strongly suggested that theywere mainly composed of cellulose, the sub-stance of all plant-cell walls and naturalfibres, and still the most abundant organicmaterial on earth. Given the advances inmonitoring technology and space vehicle con-struction, ISO represented about a foldincrease in overall sensitivity and a foldincrease in resolution over the IRAS vehicle.

Launched in Novemberthis vehiclemade many important discoveries, undoubt-edly the most interesting being that water that good old basic piece of chemistry H2O was much more abundant in the universethan had been thought hitherto. The satellitehad an estimated operational life of 18months and in Novemberit finally suf-fered the same fate as its predecessor IRAS: Its cooling fluid was exhausted.

ISOs launch was the culmination of 12years of close co-operation between Europesscientific communities and aerospace indus-tries. Work is already in hand onvehicle development and the investigationswill concentrate on the 70 to micronwavelength.

Presently of course Earth-monitoring satel-lites proliferate and Meteosat is Europescontribution to the ring of geo-synchronousweather satellites that keeps theearth under continuous observa-tion.

Ground-based telescopes too arealso used for infra-red working, theybeing provided with special interfer-ence filters and cryogenic detectorsystems. The latter eliminate obstruc-tions by infra-red radiation releasedby the detection equipment itself. Itslocation at the summit of MaunaKea on Hawaii, which peaks at14, feet or over 4, metres iscrucial, for atmospheric watervapour is a powerful absorber ofinfra-red radiation.

Equipped with aremote control arrangement, its 3. Infra-red instruments have been used to make maps of the darkterrain of Jupiters moon Io, to detecta mysterious white spot on Saturn,to observe oceans of oil on Saturnsmoon Titan and to observe stars hid-den by dust at the centre of thegalaxy.

As early as EMIscamera-tube department developedan infra-red image converter ofwhich overwere eventuallymade. Weighing a mere 7 kilos and witha range of 2, metres, Milansgoniometer which detects theinfra-red heat component of, forexample, a vehicles exhaust auto-matically maintains the projectilescourse to its target.

Another area of infra-red technol-ogy with military applications isinfra-red photography, which is usedto detect camouflage, of both per-sonnel and equipment, which it cando in fog and haze, the sort of condi-tions that not only scatters visiblelight, but are also all too common ona battlefield.

Infra-red technology has alsoinvaded scores of other areas ofactivity from archaeology and crimi-nology to search and rescue. Wehave all seen how such equipment,in the hands of police helicoptercrews, have detected intruders,escaping criminals and joy-ridersthrough television programmes suchas Police, Camera Action!

In other spheres too such as med-icine, printing and of course thehumble greenhouse, infra-red radia-tion has proved that it has far moreapplications than its discoverer everimagined! Cambridge Illus-trated History of the Worlds Science. ANatural History of the Wind. The Next Years. Headline Book Publishing, London.

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The Ultimate Guide tothe Elements. Dis-covering the Outer Solar System. TheTimes Atlas of World Exploration.

Ibid [3], Page Ch 4, Page HaasYou should use only the best components to build a high-end amplifier, ifyou want to achieve and maintain the specified performance figures. Please Note,corrections topart 1The dashed connection betweenR9 and the anode of valve V1b isnot an fdbrero wire link. In pentodemode defaultthe resistor is fit-ted in position R9, i.

This con-figuration is shown in the circuitdiagram, Figure 5. The dashedconnection has no meaning. Figure 6 does not show two back-emf suppression diodes across therelay coils.

These diodes are how-ever present on the board, as wellas included in the parts list. All resistors inthe components list are 1-percenttolerance, 0.