You can shut off the backlight option in the Palm Abbe digital refractometer by doing the following: 1. Turn the refractometer on by pressing and releasing the button. 2. Press and release the button until the display reads “LCD-Light?” / “[GO] NO.” 3. Press the Button to select “NO,” and the backlight will not come on again until reactivated. For more information about refractometer care, maintenance, and troubleshooting, please see the following MISCO page: Digital Handheld Refractometer Training.