decremeter

[ dek-ruh-mee-ter, dih-krem-i-ter ]
/ ˈdɛk rəˌmi tər, dɪˈkrɛm ɪ tər /

noun

an instrument for measuring the damping of an electromagnetic wave train.

Origin of decremeter

First recorded in 1910–15; decre(ment) + -meter