Chromatic tuners offer you the precision missing from tuning your instrument by ear. When playing a note, your chromatic tuner will detect its pitch and feed back to you what note it is nearest. It will also let you know whether you need to tune up or down to hit it exactly. Most have visual displays that do this, and provide some easy to read signal to let you know that your instrument is tuned in.
Chromatic tuners come in a variety of shapes and sizes, and their prices vary by the same degree. Most incorprate a microphone and many have a line-in for use with electrical instruments. You will find the following components in a chromatic tuner:
input device (microphone or line-in)
circuitry to detect the pitch of the note played
display to give feedback on the note you played and usually information about whether to tune up or down
Popular Chromatic Tuners
The most popular chromatic tuner, without a doubt, is the Korg CA-30 Solo Chromatic Tuner. The Korg is a high precision tool with a LCD needle-type meter for stable tuning, and is surprisingly cheap.
Tuning A Guitar Using A Chromatic Tuner
Here is an excellent how-to guide on tuning your instrument using none other than the Korg CA-30.
Here's a tutorial on how to tune your guitar using a chromatic tuner. The presenter highlights a problem that many musicians experience, in that her tuner struggles to identify correctly low notes. To get around this, she frets her string to play a higher note and tunes to that note instead. Sneaky.
For example, if your tuner has trouble picking up the low E, fret it at the third fret to play G and then tune to that G note.