Chifukwa 4-20mA?

4-20mA ndi chiyani?

Muyezo wa siginecha wa 4-20mA DC (1-5V DC) umatanthauzidwa ndi International Electrotechnical Commission (IEC) ndipo umagwiritsidwa ntchito ngati siginecha ya analogi mumayendedwe owongolera.

Kawirikawiri, chizindikiro chamakono cha zida ndi mamita chimayikidwa ku 4-20mA, ndi 4mA yomwe imayimira zochepa zamakono ndi 20mA zomwe zimayimira panopa.

N'chifukwa chiyani zotuluka panopa?

M'mafakitale, kugwiritsa ntchito chokulitsa chizindikiro kuti chikhazikike ndikutumiza ma siginecha mtunda wautali pogwiritsa ntchito ma siginecha amagetsi kumatha kubweretsa zovuta zingapo. Choyamba, ma siginecha amagetsi omwe amatumizidwa pazingwe amatha kusokoneza phokoso. Chachiwiri, kukana kogawidwa kwa mizere yotumizira kungayambitse kutsika kwamagetsi. Chachitatu, kupereka mphamvu kwa amplifier ya chizindikiro m'munda kungakhale kovuta.

Pofuna kuthana ndi mavutowa komanso kuchepetsa kukhudzidwa kwa phokoso, magetsi amagwiritsidwa ntchito potumiza zizindikiro chifukwa sichimva phokoso. Lupu lamakono la 4-20mA limagwiritsa ntchito 4mA kuimira zero chizindikiro ndi 20mA kuimira chizindikiro chokwanira, ndi zizindikiro pansi pa 4mA ndi pamwamba pa 20mA zomwe zimagwiritsidwa ntchito pa ma alarm osiyanasiyana.

Chifukwa chiyani timagwiritsa ntchito 4-20mA DC (1-5V DC)?

Zida zakumunda zimatha kugwiritsa ntchito ma waya awiri, pomwe magetsi ndi katundu zimalumikizidwa motsatizana ndi mfundo yofanana, ndipo mawaya awiri okha ndi omwe amagwiritsidwa ntchito polankhulana ndi chizindikiro komanso mphamvu pakati pa cholumikizira kumunda ndi chida chowongolera chipinda. Kugwiritsa ntchito siginecha ya 4mA DC monga poyambira kumapereka static yogwira ntchito kwa wotumizira, ndikuyika zero point yamagetsi ku 4mA DC, yomwe sagwirizana ndi zero point yama makina, imalola kuzindikira zolakwika monga kutayika kwamagetsi ndi kutha kwa chingwe. . Kuonjezera apo, dongosolo la mawaya awiri ndiloyenera kugwiritsa ntchito zotchinga zotetezera, zothandizira kuteteza kuphulika.

Zida zowongolera zimagwiritsa ntchito ma voliyumu-parallel signal transmission, pomwe zida zamtundu womwewo zimagawana malo amodzi, zomwe zimapangitsa kuti zikhale zosavuta kuyesa zida, kusintha, mawonekedwe apakompyuta, ndi zida zamagetsi.

Chifukwa chogwiritsa ntchito 4-20mA DC polumikizana ndi ma sign pakati pa zida zakumunda ndi zida zowongolera chipinda ndikuti mtunda wapakati pamunda ndi chipinda chowongolera ukhoza kukhala wofunikira, zomwe zimapangitsa kuti pakhale kukana kwa chingwe. Kutumiza ma siginecha amagetsi pamtunda wautali kumatha kubweretsa zolakwika zazikulu chifukwa cha kutsika kwamagetsi komwe kumachitika chifukwa cha kukana kwa chingwe komanso kukana kolowera kwa chida cholandirira. Kugwiritsa ntchito chizindikiro chokhazikika chazomwe zikuchitika pamayendedwe akutali kumatsimikizira kuti zomwe zikuchitika mu loop zimakhalabe zosasinthika mosasamala kanthu za kutalika kwa chingwe, kutsimikizira kulondola kwa kufalikira.

Chifukwa chogwiritsa ntchito chizindikiro cha 1-5V DC cholumikizirana pakati pa zida zowongolera ndikuwongolera zida zingapo zomwe zimalandira chizindikiro chomwecho komanso kuthandizira ma waya ndikupanga machitidwe osiyanasiyana ovuta kuwongolera. Ngati gwero lamakono likugwiritsidwa ntchito ngati chizindikiro cholumikizira, zida zambiri zikalandira chizindikiro chomwecho panthawi imodzi, zotsutsa zawo zolowetsa ziyenera kulumikizidwa motsatizana. Izi zitha kupitilira kuchuluka kwa katundu wa chida chotumizira, ndipo kuthekera kwapansi kwa zida zolandirira kungakhale kosiyana, kuyambitsa kusokoneza ndikuletsa magetsi apakati.

Kugwiritsa ntchito siginecha yamagetsi yamagetsi pamalumikizidwe kumafuna kusintha siginecha yomwe imagwiritsidwa ntchito polumikizana ndi zida zakumunda kukhala siginecha yamagetsi. Njira yosavuta ndiyo kulumikiza chopinga chokhazikika cha 250-ohm pamndandanda wapanthawi yopatsira, kutembenuza 4-20mA DC kukhala 1-5V DC. Kawirikawiri, ntchitoyi imatheka ndi transmitter.

Chithunzichi chimagwiritsa ntchito 250-ohm resistor kuti asinthe chizindikiro cha 4-20mA chamakono kukhala 1-5V voteji chizindikiro, ndiyeno amagwiritsa RC fyuluta ndi diode olumikizidwa kwa microcontroller's AD conversion pini.

"Apa adayika chithunzi chosavuta chosinthira chizindikiro cha 4-20mA kukhala siginecha yamagetsi:

Chifukwa chiyani wotumizira amasankhidwa kuti agwiritse ntchito chizindikiro cha 4-20mA DC pofalitsa?

1. Kuganizira zachitetezo cha malo owopsa: Chitetezo m'malo owopsa, makamaka pazida zomwe sizingaphulike, zimafunikira kuchepetsa kugwiritsa ntchito mphamvu zokhazikika komanso zosunthika kuti chidacho chizigwira ntchito. Ma transmitters omwe amatulutsa chizindikiro cha 4-20mA DC nthawi zambiri amagwiritsa ntchito magetsi a 24V DC. Kugwiritsa ntchito magetsi a DC makamaka chifukwa kumathetsa kufunika kwa ma capacitors akuluakulu ndi ma inductors ndipo kumaganizira kwambiri mphamvu yogawidwa ndi inductance ya mawaya olumikiza pakati pa transmitter ndi chida chowongolera chipinda, chomwe chimakhala chochepa kwambiri kuposa momwe amayatsira mpweya wa haidrojeni.

2. Kutumiza komwe kuli komweko kumakondedwa kuposa gwero lamagetsi: Zikakhala kuti mtunda pakati pa gawo ndi chipinda chowongolera ndi wokulirapo, kugwiritsa ntchito ma siginecha amagetsi pakutumiza kumatha kuyambitsa zolakwika zazikulu chifukwa cha kutsika kwamagetsi komwe kumachitika chifukwa cha kukana kwa chingwe ndi kulowetsamo. kukana kwa chida cholandira. Kugwiritsa ntchito chizindikiro chaposachedwa pamayendedwe akutali kumatsimikizira kuti zomwe zikuchitika mu chipikacho zimakhalabe zokhazikika, mosasamala kanthu za kutalika kwa chingwe, potero zimasunga kulondola kwa kufalikira.

3. Kusankhidwa kwa 20mA monga momwe zilili panopa: Kusankhidwa kwapamwamba kwambiri kwa 20mA kumachokera pamalingaliro a chitetezo, zochitika, kugwiritsa ntchito mphamvu, ndi mtengo. Zida zoteteza kuphulika zimatha kugwiritsa ntchito magetsi otsika komanso otsika. Ma 4-20mA apano ndi 24V DC ndi otetezeka kuti agwiritsidwe ntchito pamaso pa mpweya woyaka. Poyatsira gasi wa haidrojeni wokhala ndi 24V DC ndi 200mA, wokwera kwambiri kuposa 20mA. Kuphatikiza apo, zinthu monga mtunda pakati pa zida zopangira malo, katundu, kugwiritsa ntchito mphamvu, zofunikira pagawo lamagetsi, ndi zofunikira zamagetsi zimaganiziridwa.

4. Kusankhidwa kwa 4mA monga poyambira panopa: Ma transmitters ambiri omwe amatulutsa 4-20mA amagwira ntchito muzitsulo ziwiri, pomwe magetsi ndi katundu zimagwirizanitsidwa mndandanda ndi mfundo yodziwika, ndipo mawaya awiri okha amagwiritsidwa ntchito poyankhulana. ndi magetsi pakati pa transmitter yamunda ndi chida chowongolera chipinda. Kusankha kwa 4mA poyambira pano ndikofunikira kuti ma transmitter agwire ntchito. A 4mA poyambira pano, osagwirizana ndi makina a zero point, amapereka "zero point" yomwe imathandiza kuzindikira zolakwika monga kutaya mphamvu ndi kuphulika kwa chingwe.

Kugwiritsa ntchito ma siginecha a 4-20mA kumatsimikizira kusokoneza pang'ono, chitetezo, ndi kudalirika, ndikupangitsa kuti ikhale yovomerezeka kwambiri pamafakitale. Komabe, mawonekedwe ena otulutsa ma sigino, monga 3.33mV/V, 2mV/V, 0-5V, ndi 0-10V, amagwiritsidwanso ntchito kusamalira bwino ma sensa ndikuthandizira machitidwe osiyanasiyana owongolera.