You can download the SAT100 owner manual at
http://safemanuals.com/user-guide-instructions-owner-manual/SEIKO/SAT100-_E.
My SAT 100 would not recognize my acoustic strings properly. I changed batteries, tried plug/unplug the input jack, and reset all the buttons. No change. Then I tried blowing on the small hole labeled "MIC" to clear out any dust accumulation. BINGO! It will now tune my acoustic guitar just fine. Also, prop up the tuner so it faces the acoustic strings, using a playing card stuck in the groove in the rear of the tuner.