2. The "f" at the bottom of the screen indicates Fahrenheit.
3. The middle button at the bottom of the screen indicates the laser point switch, which is suitable for dark situation measurement. Instructions for use: Features of series digital thermometers: The temperature coefficients of all instruments are below 50ppm, and they can work stably within the allowable temperature range. Patents, proprietary technology and proprietary semiconductor sensor technology can achieve high linearity of 0. 1%. The sensor is specially designed.