Tsarin daidaitawa guda uku, wanda kuma ake kira girma, inji ne don auna daidaito, wanda aka sani da CMM. Kayan aiki ne mai inganci na auna daidaito wanda aka ƙirƙira a shekarun 1960. Ya samo asali ne saboda ingantaccen aikin injinan injina na atomatik da kayan aikin injinan CNC, da kuma buƙatar kayan aikin aunawa masu sauri da inganci don sarrafa sassa masu siffa mai rikitarwa.

A halin yanzu, ana amfani da ma'aunin daidaitawa uku sosai a masana'antu daban-daban kamar kera injina, masana'antar motoci, masana'antar lantarki, masana'antar sararin samaniya, da sauransu, kuma ya zama kayan aiki mai matuƙar mahimmanci don duba masana'antu na zamani da kuma kula da inganci. Ga ma'aunin mu na musamman marasa daidaito, ma'aunin daidaitawa uku kayan aiki ne na gwaji mai mahimmanci. Bayan mun sami zane-zanen samfurin abokin ciniki kuma muka tsara tsarin ma'aunin da ya dace da buƙatun samfurin kuma abokin ciniki ya gamsu, ya zama dole. Fara matakan sarrafawa a mataki na gaba, to muna buƙatar amfani da ma'aunin daidaitawa uku, saboda daidaiton na'urar kanta yana da girma sosai, don haka yi amfani da shi don gwada daidaiton kowane ɓangare na ma'aunin mu, domin ma'aunin kanta yana tabbatar da daidaiton kayan aikin dubawa. Misali, wani matsayi na ma'aunin, siffa da bayanin martabarsa sun haɗa da wasu sassan motar. Duk zamu iya samun ainihin girman ta hanyar gano ma'aunin daidaitawa.