BEFORE USE: Put the included potassium chloride powder into 20ml of pure water and mix well. Then put the probe into the solution for 24 hours, take it out and clean the residual solution on the surface of the sensitive bulb. Now, you can start to calibrate.(Note: If the sponge is wet enough, please skip this step.) DURING USE: If there is inaccurate calibration, repeat the step of 'Before Use'. If using your own potassium chloride powder, prepare the solution by adding 61.5g of KCL into 250ml of water. Then, put the probe into the solution for 24 hours, take itout and clean the residual solution on the surface of the sensitive bulb. Now, you can start to calibrate. AFTER USE: To ensure the activity of the sensitive bulb, add a drop of newly prepared potassium chloride solution into the sponge inside the probe cover. Also, to better maintain the activity of the sensitive bulb, add the solution to the sponge everytwo months. NotificationCalibrate once per week if you often test solution of PH 10, or once per half month for neutral solutions. The 250ml calibration solution for multiple uses (10ml or so each time). Then rinse the electrode with pure water before next test.Rinse and rest 3-5 min before conversing from strong acid to strong alkaline and vice versa. Clear Digital Display with Alerts Tired of squinting at a small screen to get your readings? Enjoy this PH meter's large, backlit LCD screen that displays the information in an intuitive layout so you can still see even in low visibility situations.When the PH value is lower than 3.5 or higher than 12.5, the white digital display will change to red and flash to alert you. Automatic Calibration We make your job faster and easier than ever with this convenient PH tester With the 3-point calibration procedures, your PH testing device will automatically identify the calibration solutions to give you your reading in a snap. Automatic Temperature Compensation Temperature can affect reading levels, our PH meter's automatic temperature compensation can ensure that you're getting the best possible reading. Unlike other PH meters that only have a range of 0-50 degree, ourshas a even better range of 0-70 degree, so you can test with confidence in any environment.