Digital PH Meter Tester Mini Pocket Pen for Aquarium Pool Water Calibration Features： New and. Excellent meter, very accurate and. With protective plastic case and calibration screwdriver. An ideal instrument for aquarium, fishing industry, swimming pool, school laboratory, food & beverage etc. Specification: Measuring pH Range: 0.0 - 14.0 pH Resolution: 0.1 pH Accuracy: ±0.1 pH (at 20°C/68°F), ±0.2 pH Operating Temperature: 0 - 50°C (32 - 122°F) Calibration: Manual, 1 point Relative Humidity: <95% Life: Approx.700 hours of use Size: 152mm x 30mm x 15mm (5.9x1.2x0.6") Trimming: By potentiometer Battery: 3*1.5v (AG-13 button battery) ( Not included ) Net Weight: Approx. 57g (after installed batteries) Package: 1 x Digital PH Meter Tester Pen 1 x Calibration Adjustment Screwdriver 3 x Button Cell Batteries (Not Included) 1 x User Instruction Manual (English) The way of Calibrate: the electrode in pH6.86 (under 25°C) standard buffer solution of phosphate, and gently the electrode. Note: Please allow 1-3mm errors due to manual measurement.