Thermometers have been a long standing and traditional diagnostic tool to determine the temperature of a patient. A patient's temperature, if elevated known as a fever, can be used as an indication for how severe their illness may be. Fevers are a common symptom of a number of medical conditions like infectious diseases, immunological diseases, metabolic disorder and various inflammations. For this reason, while fevers are a good indicator for illness, you should consult a medical professional for any diagnostic needs
Electronic thermometers are very common in most households and are very useful to determine whether or not your kids are really sick or simply faking. Although they may not be the most accurate, especially after prolonged use, they do provide a good idea of where someone's temperature is and whether or not they need to see a medical professional. These types of thermometers work by measuring the temperature difference between the body and the thermometer.
Infrared Thermometers take a measurement of the specific wavelength of infrared wave leaving your target area. By targeting and measuring the wave length of radiation leaving the forehead or inner ear (known as a tympanic thermometer), a infrared thermometer can calculate the temperature of the patient.
Liquid Filled Thermometers aren't commonly used anymore, however should be mentioned. These thermometers, typically made with a glass column and some kind of liquid, normally alcohol or mercury, to measure a patient's temperature. As the liquid heats up, it rises in the column and indicates a person's temperature. These types of thermometers are no longer common due to the safety hazards associated to a fragile glass column and also the toxicity of mercury.