He aha te Putanga 4 – 20mA?

Ko te putanga 4 - 20mA e pā ana ki tētahi pūnaha porowhita hiko e tohuhia ana te tohu e tētahi hiko tika-auau (DC) e rerekē ana i roto i te whānuitanga o te 4 milliamperes (mA) ki te 20mA. I konei, ko te "mA" e tohu ana i ngā milliamperes, he waeine o te hiko. I roto i tēnei pūnaha, ko te 4mA te tikanga e tohu ana i te kore, te uara iti rawa rānei o te taurangi i inehia, ko te 20mA e rite ana ki te uara mōrahi. Hei tauira, i roto i tētahi tono ine pāmahana, ka tohu pea te 4mA i te pāmahana o te 0 nekehanga Celsius, ā, ka tohu pea te 20mA i te pāmahana o te 100 nekehanga Celsius, i runga i te whakatikatika o te pūoko me te pūnaha.​

Ko te mātāpono kei muri i te putanga 4 - 20mA kei roto i tōna kaha ki te tuku mōhiohio i ngā tawhiti roa me te iti o te ātete ki te haruru hiko me te pokanoa. Kāore i rite ki ngā tohu anaro e ahu mai ana i te ngaohiko, ka taea te pāngia e te ātete i roto i ngā waea tuku me ngā mara hikohiko o waho, ka pai ake te pupuri a ngā tohu porowhita-auau i tō rātou pono. Nā te mea ka mau tonu te au e rere ana i roto i te porowhita ahakoa te ātete waea, mena ka taea e te pūtake hiko te whakarato i te ngaohiko e ranea ana hei wikitoria i te ātete i roto i te porowhita. Ka hurihia e te pūoko i te pito pūtake o te porowhita, pērā i te pūoko pēhanga, te mita rere rānei, te rahinga ā-tinana e inehia ana e ia (te pēhanga, te rere, me ētahi atu) hei au hiko i roto i te awhe 4 - 20mA. Kātahi ka haere tēnei au i roto i te ara iahiko waea-rua, waea-whā rānei ki te pito whiwhi, ka hurihia anō hei tohu whai hua, pērā i te pānui i runga i te whakaaturanga, i te tāuru rānei mō te pūnaha whakahaere.

Ko tētahi o ngā painga nui o te putanga 4 - 20mA ko tōna kaha ki te tautoko i ngā taputapu "whakakahangia e te porowhita". I roto i te whakatakotoranga whakakahangia e te porowhita, ko ngā waea e rua e kawe ana i te tohu iahiko ka tuku hiko hoki ki te pūoko, ki te tuku hiko rānei. Mā tēnei ka māmā ake te waea, ka whakaitihia hoki te utu tāutanga, inā koa i roto i ngā tipu ahumahi nui me ngā pūoko me ngā taputapu maha. Hei tāpiri, mā te paerewa 4 - 20mA ka taea te tautuhi ngāwari i ngā hapa i roto i te pūnaha. Nā te mea ehara te 0mA i te wāhanga o te awhe mahi noa (ko te iti rawa ko te 4mA), ko te pānui o te 0mA, ko te iahiko rānei i waho o te awhe 4 - 20mA he tohu i te raruraru, pērā i te waea whati, te pūoko kore mahi, te raruraru rānei ki te pūtake hiko.​

He whānuitia ngā whakamahinga o te putanga 4 - 20mA i roto i ngā ahumahi maha. I roto i te ahumahi hinu me te hau, ka whakamahia hei tuku raraunga mai i ngā pūoko e aroturuki ana i ngā tawhā pēnei i te pēhanga o te paipa, ngā tere rere wai, me ngā taumata tāke ki ngā rūma whakahaere matua. I roto i ngā whare hanga, ka āwhina i te whakahaere me te aroturuki i ngā tukanga pēnei i te pāmahana, te haumākū, me ngā kukū matū i roto i ngā tauhohenga. I roto i te rāngai aunoatanga whare, ka whakamahia ngā tohu 4 - 20mA hei whakahaere i ngā pūnaha whakamahana, whakapūhaumāota, me te hauhautanga (HVAC), me te whakarerekē i ngā tawhā i runga i ngā pānui a ngā pūoko taiao.

Hei whakamutunga, ko te putanga 4 - 20mA he tikanga taketake, he tikanga pono hoki mō te tuku tohu anaro i roto i ngā taiao ahumahi me ngā taiao whakahaere tukanga. Nā tōna pakari ki te haruru, te tautoko i ngā taputapu e whakahaerehia ana e te porowhita, me te ngāwari o te kimi hapa kua waiho hei whiringa pai mō ngā tono maha, e whakarite ana i te whakahaere maeneene me te whakahaere pai o ngā pūnaha ahumahi puta noa i te ao. I te whanaketanga tonu o te hangarau, ka taea e te paerewa 4 - 20mA te whakauru atu ki ngā kawa whakawhitiwhiti mamati hou ake, engari kei te mau tonu tōna hiranga i roto i te ao o te aunoatanga ahumahi e hangai ana ki te anaro.