The electronic thermometer LO indicates that the result of the measured body temperature exceeds the minimum human body temperature value, which is generally related to the error in the measurement method. Electronic thermometer is the use of certain substances, such as voltage, resistance, current and other physical parameters, and the environmental temperature of the connection, so as to enter the body temperature measurement. In the use of electronic thermometers for measurement, often appear to display LO situation, when this situation occurs mostly because the results of the measurement is lower than the minimum body temperature. The reasons for this situation can be the measurement distance is too far, forehead with sweat or hair cover, ate antipyretic drugs or pasted antipyretic patches, air conditioning blowing forehead, strong air currents blowing across the skin indicated, and so on. The following methods can be used to solve the problem: make sure that there is no blockage in front of the forehead, keep the measurement distance at 3~5cm, apply cold compresses for ten minutes before measurement, and avoid cold air blowing directly to the forehead.