I. Difference Between Forehead Thermometer and Mercury Thermometer
The forehead gun and the mercury thermometer operate on different principles. The mercury thermometer utilizes mercury to expand and contract in response to heat. When the body temperature reaches a certain degree, the mercury rises to a corresponding height. However, this process takes time, typically around five minutes when placed under the armpit. In contrast, the forehead thermometer employs the principle of infrared radiation to detect human body infrared radiation energy. It displays the body temperature based on the magnitude of the radiation energy, usually measuring the forehead for 1-2 seconds.
Generally, the forehead is more susceptible to external environmental factors, resulting in faster heat dissipation than the armpit. As a result, the forehead temperature is approximately 1°C lower than the armpit temperature. The forehead thermometer incorporates a temperature compensation mechanism to minimize the temperature difference with the actual body temperature, resulting in a discrepancy of about 0.1°C compared to the mercury thermometer.
II. Accuracy of Forehead Thermometers vs. Mercury Thermometers
Commonly used thermometers include mercury thermometers, electronic thermometers, forehead thermometers, and ear thermometers. Among them, the mercury thermometer is considered the most accurate due to its dense glass structure and stable mercury performance. It typically measures temperatures in the armpit, mouth, or rectum, providing more accurate readings reflective of true body temperature.
In contrast, forehead thermometers are subject to certain errors as per standard guidelines. The forehead thermometer allows an error of ±0.2°C within the range of 36-39°C and ±0.3°C when exceeding 39°C or falling below 36°C. Consequently, the accuracy of the forehead thermometer is inferior to that of the mercury thermometer. The forehead thermometer’s speed is an advantage, providing results in 1-2 seconds, albeit sacrificing a degree of accuracy. Multiple uses may be necessary to obtain more precise data.
III. Service Life of Infrared Forehead Thermometers
The infrared forehead thermometer falls under the second class of medical equipment and has a designated service life. While the package typically indicates a three-year service life, correct usage and proper storage can extend its usability. However, it is recommended to consider replacement after three years to prevent potential accuracy issues.