Thermometer general error how much is considered normal can not be generalized, because the current thermometer is divided into three kinds of mercury thermometer, electronic thermometer, infrared thermometer. In the measurement of human body temperature, the mercury thermometer error is relatively minimal, in the medical aspects of the need to identify the human body temperature, usually also to the mercury thermometer as a standard of measurement. Mercury thermometer error within 0.1-0.3 ℃ is a normal phenomenon, but the electronic thermometer error is relatively large, because the temperature will change with the outside world around the change, but also with the environmental temperature change and change, so the electronic thermometer measurement error within 0.5-1.0 ℃ are normal. In addition, the infrared thermometer is also a widely used thermometer, infrared thermometer measurement error between 0.3-0.5 ℃.