Step 1. Ensure that the thermometer is turned off. If the display is not completely dark, leave the buttons untouched for 10 seconds.
Step 2. Press and hold the ear button for 7 seconds until the display shows "- - - °C" or  "- - - °F"
Step 3. Release the ear button and immediately press it again to switch the temperature scale.
Step 4. Wait 5 seconds for the thermometer to save the settings and shut itself down before you use it again.