1.remove the protective cap. 2.first rinse the electrode with distilled water, and suck it with filter paper. 3.turn the meter on by pressing the “ON” key. 4.immerse the ph meter electrode in the solution to be tested(can not be over the immersion line ) 5.stir gently and wait around 30 seconds till the reading stabilized. 6.after finished ,clear the electrode with pure water ,turn the meter off by pressing the “ON/OFF” key. 7.Always replace the protective cap after use. Digital PH meter with LCD display 100% Brand New Weight: 65 gm Size: 15 x 3 x 1.5 cm Excellent meter, very accurate and durable Measuring pH Range: 0.0 - 14.0 pH Resolution: 0.1 pH Accuracy: ±0.1 pH (20°C), ±0.2 pH Operating Temperature: 0 - 50°C (32 - 122°F) Calibration: Manual,1 point This digital pen style pH meter is an ideal instrument for aquarium, fishing industry, swimming pool, school laboratory, food & beverage etc. Check whether the batteries contained in the product has properly placed by removing and inserting again. Calibrate the device using the buffering solution included in the box. Wipe the device with soft cloth once in every use.