A Cent is the common unit of pitch measurement, it seems, in the accordion world and is 1/100th of a semi-tone. (about 0.25Hz at 440Hz)
It relates directly to frequency (Hz) but allows a more convenient method of dealing with accordion tuning. For those who are used to ‘beats’ in dealing with tuning (as in the piano world) a convenient conversion chart (cents/frequency) is provided at Peterson Tuners (See Contacts).
The measurement of reed pitch is done with an audio tuner.
A home-made tuner (a phase-shift transistorised device),a hand-held frequency meter (Hz) and battery powered/hand-held tuners have been experimented with and all found to be insufficiently accurate and/or unstable. (Are they susceptible to temperature and battery condition?)
Favoured tuners in the accordion world appear to be the stroboscopic type such as those made by Peterson Tuners. (See Contacts).
Useful PC based tuners are available (See Contacts page). Experiments have been made with some of these and compared with a stroboscopic tuner where the error was seen to be only about 2 cents. Microphone quality and positioning is probably important for a consistent result though they seem capable of taking the reed into the area where it would have to be finished by ear anyway.