Na'ura mai kwakwalwa (psychrometer) wani nau'in hygrometer ne da ake amfani dashi don auna yanayin zafi a cikin iska. Ya ƙunshi ma'aunin zafi da sanyio biyu, ɗaya daga cikinsu shine busasshen ma'aunin zafi da sanyio, ɗayan kuma shine ma'aunin zafi da sanyio. Ma'aunin zafi da sanyio mai bushewa yana auna yanayin zafin iska, yayin da ma'aunin zafi da sanyio ya auna zafin rigar wick ɗin da aka sanya akan kwan fitila, wanda aka sanyaya shi ta hanyar ƙanƙara. Bambance-bambancen karatun zafin jiki tsakanin ma'aunin zafi da sanyio ana amfani da shi don ƙididdige yanayin zafi na iska.