Francois,
I use a Korg GA30 for my acoustic, electric and bass guitars and have had no problems. Like I said, it's cheap (I think I paid $9.95 for it) and beats tuning by ear. And if you do want to do it audibly it also gives you a tone for each sting. There are more expensive Chromatic tuners out there, Korg also makes these. I'm not an expert on them so you might want to search the net for a good guitar gear review site. Anyway, here's a link to what I have.
Korg GA30