bo·lom·e·ter 
(bō-lŏmĭ-tər)
(bō-lŏmĭ-tər)n.
An instrument that measures radiant energy by correlating the radiation-induced change in electrical resistance of a blackened metal foil with the amount of radiation absorbed.
[Greek bolē, ray; see gwelə- in the Appendix of Indo-European roots + -METER.]
bo′lo·metric (bō′lə-mĕtrĭk) adj.
bo′lo·metri·cal·ly adv.