A strobe tuner uses the physical phenomenon of “beat frequencies” to display tuning inaccuracies in the form of a moving image on a disk. Using the strobe concept, if the strobe display appears to be moving to the left then the note is flat; if the display appears to be moving to the right then the note is sharp. If the strobe display is not moving at all, then the guitar string is perfectly in tune!
True strobe tuners are used by luthiers, guitar technicians and professional recording guitarists because they are much more accurate than regular electronic tuners. Whereas a top quality rack tuner might be able to tune within 1 cent, a good strobe tuner can tune to within 0.1cent.
Strobe tuners have been around for a long time (at least since the 1950s) and are traditionally made with a mechanically spinning disk with special strobe markings. The disk spins at a fixed speed, whilst the strobe light flashes at a frequency determined by the string being tuned. The effect of the strobe light flashing on the moving disk gives the illusion of movement – difficult to describe, but surprisingly effective!
Some modern strobe tuners simulate the effect of a mechanical strobe tuner on some sort of display, dispensing with the mechanically-spinning disk but still using the same principals and visual effect.
Probably the most famous maker of Strobe Tuners is Peterson Tuners, who make an array of top end models, some of which are more akin to laboratory instruments than musician’s tools. They do, however, also make some more affordable and practical models, including handheld and pedal tuners. www.petersontuners.com
The new kid on the block for strobe tuners is Sonic Research Inc., who's Turbo Tuner range ( http://www.turbo-tuner.com ) has a very enthusiastic following. Turbo Tuners us a true strobe approach in solid state tuners, giving very fast and accurate tuners with rotating LED displays.
For further information about the scientific principles behind the workings of strobe tuners, see: