Kodi Kutulutsa kwa 4 - 20mA n'chiyani?

Kutulutsa kwa 4 - 20mA kumatanthauza dongosolo lamagetsi lozungulira komwe chizindikirocho chimayimiridwa ndi magetsi olunjika (DC) omwe amasiyana mkati mwa 4 milliamperes (mA) mpaka 20mA. Pano, "mA" imayimira milliamperes, gawo la magetsi ozungulira. Mu dongosololi, 4mA nthawi zambiri imayimira zero kapena mtengo wocheperako wa chosinthika choyezedwa, pomwe 20mA imafanana ndi mtengo wapamwamba kwambiri. Mwachitsanzo, mu ntchito yowunikira kutentha, 4mA ikhoza kusonyeza kutentha kwa madigiri 0 Celsius, ndipo 20mA ikhoza kusonyeza kutentha kwa madigiri 100 Celsius, kutengera kuwerengera kwa sensa ndi dongosolo.​

Mfundo yaikulu ya kutulutsa kwa 4 - 20mA ili mu kuthekera kwake kutumiza uthenga patali kwambiri popanda kukhudzidwa kwambiri ndi phokoso lamagetsi ndi kusokonezedwa. Mosiyana ndi zizindikiro za analog zochokera ku voltage, zomwe zingakhudzidwe mosavuta ndi kukana kwa mawaya otumizira ndi ma electromagnetic fields akunja, zizindikiro za current-loop zimasunga umphumphu wawo bwino. Izi zili choncho chifukwa mphamvu yomwe ikuyenda mu loop imakhalabe yokhazikika mosasamala kanthu za kukana kwa waya, bola ngati magetsi angapereke mphamvu yokwanira kuti agonjetse kukana mu loop. Sensor yomwe ili kumapeto kwa loop, monga sensor ya pressure kapena flow meter, imasintha kuchuluka komwe imayesa (kupanikizika, kuyenda, ndi zina zotero) kukhala mphamvu yamagetsi mkati mwa 4 - 20mA. Mphamvu iyi imadutsa mu waya wawiri kapena anayi kupita kumapeto olandirira, komwe imasinthidwa kukhala chizindikiro chogwiritsidwa ntchito, monga kuwerenga pachiwonetsero kapena cholowera cha dongosolo lowongolera.​

Chimodzi mwa ubwino waukulu wa mphamvu ya 4 - 20mA ndi kuthekera kwake kuthandizira zipangizo "zoyendetsedwa ndi lupu". Mu dongosolo loyendetsedwa ndi lupu, mawaya awiri omwewo omwe amanyamula chizindikiro chamagetsi amaperekanso mphamvu ku sensa kapena chotumizira. Izi zimapangitsa kuti mawaya azikhala osavuta komanso amachepetsa ndalama zoyikira, makamaka m'mafakitale akuluakulu okhala ndi masensa ndi zida zambiri. Kuphatikiza apo, muyezo wa 4 - 20mA umalola kuzindikira mosavuta zolakwika mu dongosolo. Popeza 0mA si gawo la magwiridwe antchito abwinobwino (osachepera ndi 4mA), kuwerenga kwa 0mA kapena mphamvu yamagetsi kunja kwa 4 - 20mA nthawi zambiri kumasonyeza vuto, monga waya wosweka, sensa yosagwira ntchito bwino, kapena vuto ndi magetsi.​

Mphamvu ya 4 - 20mA imagwiritsidwa ntchito kwambiri m'mafakitale osiyanasiyana. Mumakampani opanga mafuta ndi gasi, imagwiritsidwa ntchito kutumiza deta kuchokera ku masensa owunikira monga kuthamanga kwa mapaipi, kuchuluka kwa madzi oyenda, ndi kuchuluka kwa thanki kupita kuzipinda zowongolera. Mu mafakitale opanga, imathandizira kuwongolera ndikuwunika njira monga kutentha, chinyezi, ndi kuchuluka kwa mankhwala mu ma reactor. Mu gawo la automation yomanga nyumba, zizindikiro za 4 - 20mA zimagwiritsidwa ntchito kuyang'anira makina otenthetsera, mpweya wabwino, ndi mpweya wozizira (HVAC), kusintha magawo kutengera kuwerenga kwa masensa ozungulira.​

Pomaliza, kutulutsa kwa 4 - 20mA ndi njira yofunikira komanso yodalirika yotumizira chizindikiro cha analog m'malo opangira mafakitale ndi owongolera. Kulimba kwake motsutsana ndi phokoso, kuthandizira zida zamagetsi zoyendetsedwa ndi kuzungulira, komanso kusavuta kuzindikira zolakwika kwapangitsa kuti ikhale chisankho chokondedwa pa ntchito zambirimbiri, kuonetsetsa kuti magwiridwe antchito ndi kuwongolera bwino machitidwe a mafakitale padziko lonse lapansi. Pamene ukadaulo ukupitilirabe kusintha, muyezo wa 4 - 20mA ukhoza kuphatikizidwa ndi njira zatsopano zolumikizirana za digito, koma kufunika kwake pantchito yodziyimira payokha ya mafakitale yozikidwa pa analog kukukhazikikabe.