We don't have synonyms for dasymeter yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are dosimeter, gasometer and dosemeter.
(n) :
(dated) An instrument for testing the density of gases, consisting of a thin glass globe, which is weighed in the gas or gases, and then in an atmosphere of known density.
(n) :
(dated) An instrument for testing the density of gases, consisting of a thin glass globe, which is weighed in the gas or gases, and then in an atmosphere of known density.