Glass thermometer rrs extremely inexpensive, very smaller than average and easy to store, and don't require batteries or other special supplies. For this reason, glass thermometers are probably essentially the most widely used temperature measuring device in the house. However, glass thermometers have the disadvantage that they are certainly slow in making measurements--they typically require several minutes to reach body temperature. This is uncomfortable for the patient, and in a position to very troublesome whenever it is necessary to the temperature associated with a small child or even an invalid. In addition, glass thermometers are extremely accurate only to within a degree, may be problems errors in placement, and can be broken easily. This type of electronic thermometer has achieved wide acceptance in hospitals due to the fact is reasonably accurate, can be in combination with familiar placement techniques, and is (because of its disposable, replaceable probe covers) easily reusable with regard to the number of different patients. Although the electronic hand-held unit is itself higher priced than most households are willing to pay, the sum total of using this sort of electronic thermometer is relatively low because the disposable probe covers are inexpensive (two 3 cents per cover, for example) with a single hand-held electronic unit may work for years and used to take the temperatures of many millions of patients. Electronic thermometers offer speed, ease of reading, and accuracy improvements over glass thermometers, and also eliminate the prospect mercury poisoning. Although such electronic thermometers have achieved an honest 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 the suitable measurement. There are problems with taking a temperature from the patient's mouth due to breathing, keeping the thermometer under the patient's tongue, and also so on. Cross-contamination of infectious diseases one more a concern due to the fact mouth is a 'wet orifice.' Ear or 'tympanic' thermometers work by receiving and analyzing the radiant heat ('infrared') energy from the the eardrum. Just like you can feel the heat when you own your hands up in front of any warm fire, a tympanic thermometer can detect eardrum temperature without having to touch the eardrum by receiving the radiant heat energy coming from the eardrum. Commercially available tympanic thermometers consist a portable, hand-held battery powered main unit providing electronics, a presentation and a probe containing a special type of heat sensor such to be a 'thermopile' or a pyroelectric heat warning. This special heat sensor is highly 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 generally an integral part of the tympanic thermometer's main unit--reducing the opportunity 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 inside 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, as well as the disposable cover can be stripped off the instrument and discarded.