Using the Calibration Feature of the AQA 4500 Waterproof Digital Thermometer

You can check the accuracy of the probe by using an ice slurry.

Make some ice cubes from distilled (or de-ionized) water.  Regular tap water is OK, but not as good as distilled. Fine-crush the ice to a slurry in a blender. If you have ever had a "slushy" or a well-made margarita you know the consistency... Stir the ice rapidly (add some more water if you need more liquidity) with the probe shaft immersed in the middle of the ice slurry-- the stirring needs to be brisk! After immersion an stirring of the mixture with the probe tip, the AQA 4500 should read pretty close to 32°F (0 °C) Keep the tip in the slurry, and press the ON/OFF button for 8 seconds to enter the calibration mode (you will see the blinking message "CAL" on the LCD display on the upper right).  When you see the "CAL" release the ON/OFF button. Keep stirring. When the reading stabilizes at the lowest reading, press the CAL button on the AQA 4500 (its the small silver button below the other buttons.  The display on the until will then show  32°F (0 °C).  You have just calibrated the unit.

 Keep a record of your calibration if this if for a regulated quality or safety program: who did it, when, and a description of the procedure.