PHscan series pocket pH tester includes models 10, 20, 30 for the measurement of acidity and alkalinity in liquids. These testers are designed for outdoor applications, especially waste water treatment and environmental monitoring. Automatic Calibration The testers allows up to 2 points calibration. Press the CAL key and the screen will shows the standard buffer pH needed for calibration. Immerse the pH electrode into the calibration solution as indicated and press CAL key. The tester is now automatically calibrated. Hold Function During the measurement, press the HOLD key, the testers will freeze the reading momentarily on the display for easy viewing or recording. Automatic Temperature Compensation PHscan 30 tester with a temperature sensor, press the temperature key, the meter will shows current temperature values. Automatic Temperature Compensation provides highly accurate measurement over the entire pH ranges. Replaceable Electrode Design Generally, the pH electrode' s effective life is one year, if you use it more than this time, the measured value possible produceds offset, it will serious influence the measurement accuracy of tester. PHscan series tester has a double-junction sensor, you can easily replace the new electrode. Auto-Power Off The testers will automatically power down 8 minutes after the last key press. This function is helpful to save battery. It can also be turned off manually. Waterproof Feature O- ring seals on the screw - tight battery and sensor compartments prevent water damage even if fully immersed. If the tester sink into the water, it will float automatically.