Idan muka daidaita nau'ikan ma'aunin zafi daban-daban, misali ma'aunin zafi na mercury da ma'aunin zafi na barasa, ma'aunin ma'aunin zafi biyu iri ɗaya ne kawai a 0 oC (ko 32 oF ) da 100 oC (ko 212 oF ). Idan muka yi amfani da ma'aunin zafi biyu don auna zafin iska, lambobin da kowace ma'aunin zafi ya nuna ba lallai ne su zama iri ɗaya ba. Wataƙila ma'aunin zafi na mercury yana nuna 48 oC , yayin da ma'aunin zafi na barasa yana nuna 46 oC . Wannan saboda yawan faɗaɗa mercury da barasa ya bambanta. Haka kuma da sauran nau'ikan ma'aunin zafi, kamar ma'aunin zafi na bimetallic, da sauransu. Ma'aunin zafin da aka ƙayyade ta wannan hanyar ya dogara sosai akan halayen kayan da aka yi amfani da su.
Domin kuwa ma'aunin zafin da aka kafa ta amfani da ma'aunin zafi na yau da kullun yana da nasa matsalolin, muna buƙatar ma'aunin zafi na yau da kullun. Ma'aunin zafi na yau da kullun yana ba mu damar kafa ma'aunin zafin da ya fi daidai ba tare da dogaro da halayen wani abu ba.
Ma'aunin zafi mai kusan cikakke shine ma'aunin zafi mai ƙarfi na gas . Ka'idar aiki na ma'aunin zafi mai ƙarfi na gas kamar haka: Girman iskar gas ɗin yana kasancewa daidai, ko ba a canza shi ba. Yayin da zafin jiki ke ƙaruwa, matsin iskar gas ɗin ma yana ƙaruwa.
A cikin bututu 1 da 2 akwai mercury. Ana kiyaye yawan iskar gas ta hanyar ɗagawa ko rage bututu 2 don haka matakin mercury a cikin bututu 1 koyaushe yana kan alamar tunani. Idan zafin ya ƙaru, matsin iskar gas a cikin bututun shima yana ƙaruwa. Saboda haka, dole ne a ɗaga bututu 2 sama don ƙarar iskar gas ta kasance iri ɗaya. Ana iya tantance matsin iskar gas ta hanyar karanta tsayin ginshiƙin mercury (h) a cikin bututu 2. Idan ana amfani da hanyar hannu, kawai ku tuna cewa ginshiƙin mercury mai tsayi 760 mm = 1 atm (1 yanayi) na matsin lamba. A cikin ma'aunin zafi na gas mai ƙarfi, akwai riga akwai na'urar auna matsin lamba. An kuma tsara akwati da ke ɗauke da iskar don iskar ta kasance koyaushe tana da girma mai daidaito. Don haka abin da ake aunawa shine canjin matsin lamba kawai.
Domin daidaita ma'aunin zafi na gas mai yawan gaske, za mu iya auna matsin lamba na gas a yanayin zafi biyu. Misali, bari mu yi amfani da yanayin zafin kankara da na tururi. Ana daidaita ma'aunin zafi na gas mai yawan gaske a matsin lamba na atm 1. Matakan da za a bi don daidaita ma'aunin zafi sune kamar haka.
Da farko, ana saka silinda mai iskar gas a cikin akwati da ke ɗauke da kankara da ruwa. Ana kiyaye yawan iskar gas ɗin akai-akai, don haka dole ne a rage bututun 2 don matakin mercury a cikin bututun 1 ya kasance a wurin da ake tunani. Idan yawan iskar gas bai canza ba, a rubuta tsayin ginshiƙin mercury (h) a cikin bututun 2. Yi amfani da h don ƙididdige matsin lamba. Idan ana amfani da ma'aunin zafi mai ƙarfi na gas, silinda da ke ɗauke da iskar za a nutsar da ita kai tsaye cikin akwati da ke ɗauke da kankara da ruwa. Akwai ma'aunin matsin lamba. A rubuta matsin iskar gas (bari mu ce wannan matsin lamba 1 ne ko P 1 )
Na biyu, Ana saka silinda mai iskar gas a cikin akwati da ke ɗauke da ruwa da ake dumamawa. Domin kiyaye yawan iskar gas akai-akai, ana ɗaga bututun 2 ta yadda matakin mercury a cikin bututun 1 zai ci gaba da kasancewa a wurin da ake amfani da shi. Idan yawan iskar gas bai canza ba, a rubuta tsayin ginshiƙin ruwa. 
Mercury (h) a cikin bututu 2. Yi amfani da h don ƙididdige matsin lamba na iskar gas (bari mu ce wannan matsin lamba 2 ne ko P2)
Na uku , ƙirƙiri jadawali wanda ke nuna alaƙar da ke tsakanin matsin lamba da zafin jiki. Duba misali a ƙasa.
P 1 shine matsin lamba na iskar gas a zafin wurin kankara (0 oC ) kuma P 2 shine matsin lamba na iskar gas a zafin wurin tururi (100 oC ). Zana layi wanda ke haɗa wurin haɗuwa na P 1 da 0 oC da kuma wurin haɗuwa na P 2 da 100 oC . Ta hanyar komawa ga jadawalin, kodayake mun san matsin lamba na iskar gas kawai, ana iya sanin zafin cikin sauƙi har ma a yi hasashensa.
Sikelin Kelvin
Idan an zana layin da ke kan jadawalin da ke sama don ya haɗu da ma'aunin T o C, to lokacin da matsin lamba na iskar gas = 0, zafin iskar gas = -273,15 o C. Wataƙila muna tunanin cewa zafin iskar gas a matsin lamba 0 ya bambanta, ya danganta da nau'in iskar gas a cikin bututun ma'aunin zafi na iskar gas mai ɗorewa. Dangane da gwaje-gwaje, kodayake nau'in iskar gas ya bambanta, lokacin da matsin lamba na iskar gas ya zama sifili, zafin jiki koyaushe yana -273,15 o C. Don haka, za mu iya amfani da wannan zafin jiki a matsayin ma'aunin zafin jiki na yau da kullun (wanda kuma aka sani da zafin jiki na sifili). Wannan zafin jiki na sifili na sifili ana kiransa da sunan laƙabi na sifili na sifili ko sikelin Kelvin. Kelvin shine sunan marigayi Lord Kelvin (1824-1907), tsohon masanin kimiyyar lissafi na Burtaniya.
A wannan ma'aunin, ana nuna zafin jiki a Kelvin (K), ba digiri Kelvin ba (K).oK). Tazarar da ke tsakanin digiri iri ɗaya ce da ta sikelin Celsius, amma ƙimar sifili an canza ta zuwa 0 K. Don haka 0 K = -273,15 oC da 273,15 K = 0 oC. Za a iya canza zafin jiki a sikelin Celsius zuwa sikelin Kelvin ta hanyar ƙara 273,15. Haka nan, za a iya canza zafin jiki a sikelin Kelvin zuwa sikelin Celsius ta hanyar cire 273,15.
T (K) = T (oC) + 273,15
T (oC) = T (K) – 273,15
Misali tambaya 1.40 oC = …. K
T(K) = T(C) + 273
T = 20 + 273
T = 293 K
Misali tambaya ta 2. 80 o F = …. K
