Ear thermometers were created out of a need to find a more comfortable and convenient method for taking a person’s body temperature. For many people, the idea of getting a traditional rectal thermometer test was extremely embarrassing and unpleasant.
Getting a restless child to sit still while holding a thermometer in their mouth proved to be equally as nerve-racking. In addition, many mercury thermometers are difficult to read and are prone to breakage. For many people, ear thermometers provided a more comfortable and user-friendly alternative.
Ear thermometers work by picking up infrared radiation emissions from the eardrum and using them to calculate body temperature.
Since the eardrum is very sensitive, a thermometer cannot actually touch it without causing serious damage. Therefore, a remote sensing method must be used to determine body temperature. That is where infrared radiation comes in. Infrared radiation, also referred to as heat or thermal radiation, is used to determine the temperature of remote objects.
This type of radiation occupies the part of the electromagnetic spectrum at the end of the visible red light band. Infrared radiation has the same properties as light, with the ability to be illuminated and reflected. The amount of radiation emitted determines the temperature of the object being examined.
While humans can detect objects and elements that radiate large amounts of heat such as a fire or a hot stove, they are not able to detect smaller, subtler changes in heat or infrared radiation.
It takes special heat-sensitive instruments such as thermometers to read these changes. Ear thermometers use sensors to detect infrared radiation and measure the temperature of the eardrum. One of the most common sensors used in infrared devices is the thermopile.
A thermopile is a voltage-generating sensor that measures radiation by means of temperature changes. Thermopile detectors are able to respond quickly to the thermal radiation that the eardrum emits. This device is very sensitive to the subtle, often unnoticeable changes in infrared radiation. When you place the thermometer in your ear, the thermopile makes an assessment of the infrared emission of the eardrum.
Since the heat radiation emitted from the eardrum is characteristic of its temperature, a quick study of the ear using a thermometer is enough to determine a person’s body temperature. Within seconds, the thermal radiation that the eardrum generates is measured and then converted to actual temperature, usually within one-tenth of a degree.
A beep will then sound to signal the end of the temperature measurement. The reading is then displayed on the screen, where it can be visible to the user. Most ear thermometers use an LCD screen to display their readings.
Users should be aware that since ear thermometers use a remote sensing method such as infrared radiation to determine body temperature, the reading might not be as accurate as it would be with a traditional thermometer. Depending on the expertise of the user, ear thermometers can be as much as half of a degree to 2 degrees off.
This may prove to be problematic in situations where a person’s temperature needs to be strictly monitored, as is the case for persons with seizure disorders or weakened immune systems.
To combat this problem, ear thermometers have developed improved sensors that are closer to the eardrum, allowing greater accuracy. Ear thermometers are also now being equipped with a special insulation to prevent outside factors (such as earwax and bacteria) to interfere with the reading.