PEN PH METER Model : PH-222 * 0 to 14.00 pH. * ATC (auto temperature compensation). * Auto calibration for pH 4, pH 7 or pH 10. * Meter with pH electrode, all in one. * IP-67, water proof. * Easy replacement for the pH electrode. * Pen type, easy carry out. * Data logger. * pH 4, pH 7 standard solution are included. * DC 1.5V battery ( UM-4, AA ) x 4, long life.