[. . . ] Skincheck · Skincheck 1 HI 98109 · HI 98110 pH Testers for Skin Dear Customer, Thank you for choosing a Hanna product. Please read carefully this instruction manual before using the instrument. [. . . ] Batteries should only be replaced in a safe area using the battery type specified in this instruction manual. CALIBRATION · For best results, calibrate frequently. · Dip the tip of the electrode (4 cm/ 1½") in pH 7. 01 buffer solution at room temperature. · Use a small screwdriver to adjust the pH7 trimmer until the display reads "pH 7. 01". · Rinse the electrode with water and dip it in pH 4. 01 (or pH 10. 01) buffer solution. · With a small screwdriver adjust the pH4/10 trimmer until the display reads "pH 4. 01" (or "pH 10. 01"). ALWAYS CALIBRATE USING FRESH BUFFER SOLUTIONS. WARRANTY These meters are guaranteed for one year against defects in workmanship and materials when used for its intended purpose and maintained according to instructions. Damages due to accident, misuse, tampering or lack of prescribed maintenance are not covered. If service is required, contact the dealer from whom you purchased the instrument. If under warranty, report the model number, date of purchase, serial number and the nature of the failure. If the repair is not covered by the warranty, you will be notified of the charges incurred. If the instrument is to be returned to Hanna Instruments, first obtain a Returned Goods Authorization Number from the Customer Service department and then send it with shipment costs prepaid. When shipping any instrument, make sure it is properly packaged for complete protection. INITIAL PREPARATION The pH electrode is shipped dry. [. . . ] To avoid electrical shocks, do not use this instrument when voltage at the measurement surface exceeds 24 Vac or 60 Vdc. To avoid damage or burns, do not perform any measurement in microwave ovens. [. . . ]