If it is the first time to use the thermometer, follow the following steps: Step 1: Place the thermometer at a stable ambient temperature for more than 30 minutes; Step 2: Measure someone with a conventional mercury or electronic thermometer, assuming a temperature of 36.8 degrees Celsius; Step 3: Use a non-contact infrared thermometer to measure the same person, pay attention to the measurement distance and measurement method: Keep the thermometer 1-3 cm away from your forehead, and remove any obstacles that might interfere with the measurement, such as hair and sweat. If you get the same temperature of 36.8 degrees Celsius, the thermometer is set and can be used normally. If you get a lower reading of 36.4 degrees Celsius, a difference of 0.4 degrees Celsius, You can set F1 to "0.4 ° C", or vice versa, for 0.4 ° C more, you can set F1 to "-0.4 ° C".