Yuav ua li cas yog tus yam ntxwv ntawm impedance

Ib tug ntawm cov tsis yog tej conductive kab ntxwv impedance. Ntawm kev tseeb nws acquires ib tug high-zaus xov tooj cua kis tau tus mob cov txheej txheem, qhov twg lub slightest mismatch Circuit Court lag luam ua rau teeb meem loj distortions nyob rau hauv lub tso zis. Nyob rau lwm cov tes, txhua lub yas dhos ntawm ib tug computer txuam nrog rau lwm yam nyob rau hauv ib lub zos network, ntsib txhua txhua hnub sij hawm "yam ntxwv impedance." Nws yuav tsum tau muab sau tseg tias cov tsos ntawm Ethernet tes hauj lwm ntawm cov khub muab lub cov neeg siv kawg tsis txhawj txog kev connectors, earthing, raws li connectors thiab terminators, raws li yog cov ntaub ntawv nrog lub coaxial cable kab 10 megabit (los yog tsawg dua). Txawm li cas los, txawm muaj kev sib hwm mus rau lub twisted khub, lub sij hawm "yam ntxwv impedance" yog muaj feem xyuam. Feem ntau, nyob rau hauv lub lag luam los ntawm lub computer tes hauj lwm tshwj xeeb tshaj yog tseem ceeb tom qab.

Yog li ntawd, dab tsi yog yam ntxwv impedance? Raws li twb tau hais, qhov no yog ib tug ntawm cov yam ntxwv ntawm cov conductive kab rau lub hauv paus ntawm nws yog xim hlau conductors. Qhov kawg clause yog tsim nyog nyob rau hauv thiaj li tsis mus sib tov niaj hnub kho qhov muag cov ntaub ntawv kis tau tus mob kab thiab classic tooj liab nyob ntawm tej, uas yog lub zog muaj tsis them hais thiab lub teeb - muaj lwm yam kev cai. Qhov no tus nqi qhia ib tug kab muaj cov kuj nqi generator (qhov chaw modulated hluav taws xob oscillations). Tsis txhob xav yuam kev rau kuj, uas yuav tsum tau ntsuas los ntawm cov pa multimeter, thiab tus yam ntxwv ntawm impedance ntawm qhov chaw, raws li lawv yog cov tag tej yam txawv. Cov yav tas tsis yog nyob ntawm seb qhov ntev ntawm tus neeg xyuas pib (qhov no yog twb txaus rau kos xaus hais txog tus "kev zoo sib thooj" ntawm kuj). Lub cev, nws yog sib npaug zos rau cov square hauv paus ntawm tus piv ntawm inductance (Henry) rau muaj peev xwm (Farad). Ib tug me me hais txog: txawm lub fact tias cov lus teb siv reactive Cheebtsam ntawm cov kab, nthwv dej kuj ntawm lub Circuit Court yog ib txwm nyob rau hauv cov lus teb yog suav tias yog kom nquag plias.

Nws yog qhov zoo tshaj plaws yuav tau xav txog tag nrho cov ntawm cov piv txwv. Xav txog tej yam ib tug yooj yim Circuit Court muaj ib lub hwj chim qhov twg los (generator, R1), lub conductors muaj ib tug yam ntxwv impedance (R2), thiab tus neeg (load, R3). Nyob rau hauv cov ntaub ntawv ntawm koob pheej ntawm lawv ntawm tag nrho cov peb resistances tag nrho cov kis zog nce mus txog tus neeg thiab nws ua pab ua hauj lwm. Yog hais tias nyob rau hauv tej ib feem ntawm no kab zauv tsis txaus siab, muaj yog ib tug Hloov lub lag luam. Thaum lub point qhov twg lub kab lawm, muaj ib tug reflected yoj, thiab ib feem ntawm cov electromagnetic zog rov qab los - mus rau lub generator. Raws li, nws yog tsim nyog los ua rau kom nws cov hwj huam pab kom txawm peem rau qhov ntau ntawm cov thaws rov los lub zog. Nyob rau hauv lwm yam lus, ib feem ntawm lub zog yog siv "tsis muaj dab tsi", uas txhais tau tias poob thiab non-pom lub lag luam. Nyob rau hauv tas li ntawd, nyob rau hauv tej rooj plaub, lub mismatch feem ntau cuam tshuam hauj lwm ntawm tag nrho cov kab.

Tam sim no rov qab mus rau lub computer network, qhov twg yoj kuj plays ib qho tseem ceeb luag hauj lwm. Rau cov kab raws li nyob rau hauv lub coaxial cable (50 ohm) yog ib qho tseem ceeb rau hwm lub tej yam kev mob: kuj network phaib thiab cov neeg xyuas pib ntawm lawv yuav tsum tau sib npaug. Tsuas yog nyob rau hauv cov ntaub ntawv no, tej hauj lwm txiav thiab grounding system. Yog hais tias tej feem ntawm lub cable kab yog lub cev ib tug me ntsis stretch (mus dai rau ntawm lub load neeg xyuas pib), ces vim cov kev hloov nyob rau hauv lub cheeb ntawm lub conductors nyob rau hauv qhov chaw no yuav hloov cov yam ntxwv impedance, muaj yuav thaws rov los yoj, txhawm cia tus system. Nyob rau hauv rooj plaub no tus ntsuas active kuj kab tej zaum yuav tsis hloov ntau heev (tsis tshua muaj nqi li tsis sau npe nce nyob rau hauv kuj). Attempts mus rov qab kho cov kab conductors ntawm soldering rau cov puas feem ntxiv aggravate qhov teeb meem no, vim hais tias nws yuav tsis tau tsuas yog hloov tsis kam, thiab ib tug sib tov ntawm txawv kev kawm (tin, tooj liab) nyob rau hauv uas tsis propagate txawv.

Raws li nrov li ib tug twisted khub qeb 5 yam ntxwv impedance yog 100 ohms. Tsaug rau no rov qab tej zaum yuav soldered, thiab txawm sib ntswg.