to·nom·e·ter 
(tō-nŏmĭ-tər)
(tō-nŏmĭ-tər)n.
1. Any of various instruments for measuring pressure or tension.
2. An instrument for measuring hydrostatic pressure within the eyeball, used to detect glaucoma.
3. Music An instrument, such as a graduated set of tuning forks, used to determine the pitch or vibration rate of tones.
[Greek tonos, tension; see TONE + -METER.]
to′no·metric (tō′nə-mĕtrĭk) adj.
to·nome·try n.