CRT invention Oscilloscope history

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the interior of cathode-ray tube use in oscilloscope. 1. deflection voltage electrode; 2. electron gun; 3. electron beam; 4. focusing coil; 5. phosphor-coated inner side of screen


cathode ray tubes (crts) developed in late 19th century. @ time, tubes intended demonstrate , explore physics of electrons (then known cathode rays). karl ferdinand braun invented crt oscilloscope physics curiosity in 1897, applying oscillating signal electrically charged deflector plates in phosphor-coated crt. braun tubes laboratory apparatus, using cold-cathode emitter , high voltages (on order of 20,000 30,000 volts). vertical deflection applied internal plates, face of tube observed through rotating mirror provide horizontal time base. in 1899 jonathan zenneck equipped cathode ray tube beam-forming plates , used magnetic field sweeping trace.


early cathode ray tubes had been applied experimentally laboratory measurements 1919 suffered poor stability of vacuum , cathode emitters. application of thermionic emitter allowed operating voltage dropped few hundred volts. western electric introduced commercial tube of type, relied on small amount of gas within tube assist in focussing electron beam.


v. k. zworykin described permanently sealed, high-vacuum cathode ray tube thermionic emitter in 1931. stable , reproducible component allowed general radio manufacture oscilloscope usable outside laboratory setting.


the first dual-beam oscilloscope developed in late 1930s british company a.c.cossor (later acquired raytheon). crt not true double beam type used split beam made placing third plate between vertical deflection plates. used during wwii development , servicing of radar equipment. although extremely useful examining performance of pulse circuits not calibrated not used measuring device. was, however, useful in producing response curves of if circuits , consequently great aid in accurate alignment.


allen b. du mont labs. made moving-film cameras, in continuous film motion provided time base. horizontal deflection disabled, although slow sweep have spread phosphor wear. crts p11 phosphor either standard or available.


long-persistence crts, used in oscilloscopes displaying changing signals or single-shot events, used phosphor such p7, comprised double layer. inner layer fluoresced bright blue electron beam, , light excited phosphorescent outer layer, directly visible inside envelope (bulb). latter stored light, , released yellowish glow decaying brightness on tens of seconds. type of phosphor used in radar analog ppi crt displays, graphic decoration (rotating radial light bar) in tv weather-report scenes.








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