Waterproof ph meter with backlight Specifications Range 0.0 to 14.0 ph Resolution:     0.1 ph Accuracy : ±0.01 ph Typical emc deviation  ±0.1 ph Calibration:  manual, 1 point, Temperature compensation automatic: 0 to 50 Environment:  0 to 50 (32 to 122f); Rh max 95% Battery type   4 x 1.5v alkaline Battery life approx. 200 hours of use Dimensions 152 x 30 x 21 mm (5.9 x 1.2 x 0.8") Weight:     53 g Operation Remove the protective cap. Do not be alarmed if white crystals Appear around the cap. This is normal with ph electrodes and They dissolve when rinsed with water. Turn the meter on sliding the switch on the top. Immerse into solution up to the max immersion level.                                         ?¢ stir gently and wait until the display stabilizes. Readings are automatically compensated for temperature variations. After use, switch off ph meter, use the water clean the electrode and replace the protective cap. Do not use distilled or deionized water for storage purposes. Large fluctuations in readings could be due to lack of calibration, dry electrode or rundown batteries. Calibration Immerse the tester up to the maximum immersion level in ph 6.86 buffer solution Allow the reading to stabilize and using a small screwdriver adjust the calibration trimmer to read 6.9. Calibration is now complete. Always use fresh buffers for calibration. Battery replacement When the meter cannot be switched on or the display fades, pull out the battery compartment and replace all three 1.5v batteries, while paying attention to their polarity. Batteries should only be replaced in a safe area using the battery type specified in this instruction manual.