Features of Lutron PH-222 Pen-Type Digital pH and Temperature Meter pH4, pH7 standard solution are standard accessories Easy to change the pH value of the electrode Temperature measurement ℃ and ℉ IP67, water proof and protection. Auto calibration is done for pH 4, pH 7 or pH 10 or other value. Very high input impedance. Data hold function for freezing the desired value obtained. Provided with auto power off. Records maximum and minimum value with recall. 100 point data logger with recall is available Microcomputer circuit, intelligent function, high accuracy. Compact in size, light weight. Power supply of DC 1.5 V battery ( UM4/AAA ) x 4 Pieces.