Tympanic thermometer with modular sensing probe
Glass thermometer is very inexpensive, very small and easy to store, and don’t require batteries or other special supplies. For this reason, glass thermometers are probably the most widely used temperature measuring device in the home. However, glass thermometers have the disadvantage that they are very slow in making measurements–they typically require several minutes to reach body temperature. This is uncomfortable for the patient, and may be very troublesome when it is necessary to take the temperature of a small child or an invalid. In addition, glass thermometers are typically accurate only to within a degree, may be susceptible to errors in placement, and can be broken easily.
This type of electronic thermometer has achieved wide acceptance in hospitals because it is reasonably accurate, can be used with familiar placement techniques, and is (because of its disposable, replaceable probe covers) easily reusable for a number of different patients. Although the electronic hand-held unit is itself more expensive than most households are willing to pay, the overall cost of using this kind of electronic thermometer is relatively low because the disposable probe covers are inexpensive (two to three cents per cover, for example) and a single hand-held electronic unit may last for years and can be used to take the temperatures of many thousands of patients.
Electronic thermometers offer speed, ease of reading, and accuracy improvements over glass thermometers, and also eliminate the possibility of mercury poisoning. Although such electronic thermometers have achieved a fair degree of success, they have certain significant disadvantages. For example, they need to be constantly calibrated, are relatively easily broken, and often require a relatively long time (thirty seconds or more in many cases) to make an accurate measurement. There are also problems with taking a temperature from the patient’s mouth due to breathing, keeping the thermometer under the patient’s tongue, etc. Cross-contamination of infectious diseases is also a concern because the mouth is a “wet orifice.”
Ear or “tympanic” thermometers work by receiving and analyzing the radiant heat (“infrared”) energy coming from the eardrum. Just as you can feel the heat when you hold your hands up in front of a warm fire, a tympanic thermometer can detect eardrum temperature without having to actually touch the eardrum by receiving the radiant heat energy coming from the eardrum.
Commercially available tympanic thermometers consist of a portable, hand-held battery powered main unit providing electronics, a display and a probe containing a special type of heat sensor such as a “thermopile” or a pyroelectric heat sensor. This special heat sensor is especially sensitive to the eardrum’s radiant heat energy. Microelectronics can determine eardrum temperature from the electrical signals provided by the special heat sensor. The thermopile’s sensing probe is typically an integral part of the tympanic thermometer’s main unit–reducing the potential for breakage of the sensor assembly and (at least potentially) increasing reliability and accuracy.
To use the ear thermometer, a nurse or other care provider inserts a disposable probe cover onto the instrument’s sensing probe. Once the disposable probe cover is in place, the nurse or other caregiver inserts the covered sensing probe into the patient’s outer ear and then presses a button to command the instrument to make a measurement. The measurement time is usually very rapid–on the order of two seconds or less. The patient’s temperature instantly shows on the instrument’s display. The instrument may then be removed from the patient’s ear, and the disposable cover can be stripped off the instrument and discarded.
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