Medical Thermometer
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A medical thermometer or clinical thermometer is a device used for
measuring Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events. In other words, measurement is a process of determining how large or small a physical quantity is as compared to ...
the
body temperature Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...
of a human or other animal. The tip of the thermometer is inserted into the
mouth A mouth also referred to as the oral is the body orifice through which many animals ingest food and animal communication#Auditory, vocalize. The body cavity immediately behind the mouth opening, known as the oral cavity (or in Latin), is also t ...
under the
tongue The tongue is a Muscle, muscular organ (anatomy), organ in the mouth of a typical tetrapod. It manipulates food for chewing and swallowing as part of the digestive system, digestive process, and is the primary organ of taste. The tongue's upper s ...
(''oral'' or ''sub-lingual temperature''), under the
armpit The axilla (: axillae or axillas; also known as the armpit, underarm or oxter) is the area on the human body directly under the shoulder joint. It includes the axillary space, an anatomical space within the shoulder girdle between the arm an ...
(''axillary temperature''), into the
rectum The rectum (: rectums or recta) is the final straight portion of the large intestine in humans and some other mammals, and the gut in others. Before expulsion through the anus or cloaca, the rectum stores the feces temporarily. The adult ...
via the
anus In mammals, invertebrates and most fish, the anus (: anuses or ani; from Latin, 'ring' or 'circle') is the external body orifice at the ''exit'' end of the digestive tract (bowel), i.e. the opposite end from the mouth. Its function is to facil ...
(''rectal temperature''), into the
ear In vertebrates, an ear is the organ that enables hearing and (in mammals) body balance using the vestibular system. In humans, the ear is described as having three parts: the outer ear, the middle ear and the inner ear. The outer ear co ...
(''tympanic temperature''), or on the
forehead In human anatomy, the forehead is an area of the head bounded by three features, two of the skull and one of the scalp. The top of the forehead is marked by the hairline, the edge of the area where hair on the scalp grows. The bottom of the fo ...
(''temporal temperature'').


History

The medical thermometer began as an instrument more appropriately called a water
thermoscope A thermoscope is a device that shows changes in temperature. A typical design is a tube in which a liquid rises and falls as the temperature changes. The modern thermometer gradually evolved from it with the addition of a scale in the early 17th c ...
, constructed by
Galileo Galilei Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642), commonly referred to as Galileo Galilei ( , , ) or mononymously as Galileo, was an Italian astronomer, physicist and engineer, sometimes described as a poly ...
circa 1592–1593. It lacked an accurate scale with which to measure temperature and could be affected by changes in atmospheric pressure.
Italian Italian(s) may refer to: * Anything of, from, or related to the people of Italy over the centuries ** Italians, a Romance ethnic group related to or simply a citizen of the Italian Republic or Italian Kingdom ** Italian language, a Romance languag ...
physician
Santorio Santorio Santorio Santorio (29 March 1561 – 25 February 1636) whose real name was Santorio Santori (or de' Sanctoriis) better known in English as Sanctorius of Padua was an Italian physiologist, physician, and professor, who introduced the quantitative ...
is the first known individual to have put a measurable scale on the thermoscope and wrote of it in 1625, though he possibly invented one as early as 1612. His models were bulky, impractical and took a fair amount of time to take an accurate oral reading of the patient's temperature. Two individuals switched from water to alcohol in the thermometer. * The earliest is
Ferdinando II de' Medici, Grand Duke of Tuscany Ferdinando II de' Medici (14 July 1610 – 23 May 1670) was Grand Duchy of Tuscany, grand duke of Tuscany from 1621 to 1670. He was the eldest son of Cosimo II de' Medici, Grand Duke of Tuscany, Cosimo II de' Medici and Archduchess Maria Mad ...
(1610–1670), who created an enclosed thermometer that used alcohol circa 1654. *
Daniel Gabriel Fahrenheit Daniel Gabriel Fahrenheit FRS (; ; 24 May 1686 – 16 September 1736) was a physicist, inventor, and scientific instrument maker, born in Poland to a family of German extraction. Fahrenheit invented thermometers accurate and consistent enough t ...
(1686–1736), a Polish-born Dutch physicist, engineer, and glass blower, made contributions to thermometers as well. He created an alcohol thermometer in 1709 and later innovated the mercury thermometer in 1714. Mercury, he found, responded more quickly to temperature changes than the previously used water. Fahrenheit also created the temperature scale which is named after him, having recorded the system in 1724. The scale is still only mainly used for everyday applications in the
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, its territories and associated states (all served by the U.S. National Weather Service) as well as
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,
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, and the Cayman Islands.Encyclopædia Britannica "Science & Technology: Daniel Gabriel Fahrenheit

/ref> Prominent Dutch mathematician, astronomer and physicist
Christiaan Huygens Christiaan Huygens, Halen, Lord of Zeelhem, ( , ; ; also spelled Huyghens; ; 14 April 1629 – 8 July 1695) was a Dutch mathematician, physicist, engineer, astronomer, and inventor who is regarded as a key figure in the Scientific Revolution ...
created a clinical thermometer in 1665, to which he added an early form of the
Celsius The degree Celsius is the unit of temperature on the Celsius temperature scale "Celsius temperature scale, also called centigrade temperature scale, scale based on 0 ° for the melting point of water and 100 ° for the boiling point ...
scale by setting the scale to the freezing and boiling points of water. By 1742 Swedish astronomer
Anders Celsius Anders Celsius (; 27 November 170125 April 1744) was a Swedes, Swedish astronomer, physicist and mathematician. He was professor of astronomy at Uppsala University from 1730 to 1744, but traveled from 1732 to 1735 visiting notable observatories ...
created the
Celsius The degree Celsius is the unit of temperature on the Celsius temperature scale "Celsius temperature scale, also called centigrade temperature scale, scale based on 0 ° for the melting point of water and 100 ° for the boiling point ...
temperature scale that was the reverse of the modern scale, in that ''0'' was the boiling point of water, while ''100'' was freezing. It was later reversed by Swedish botanist Carolus Linnaeus (1707–1778) in 1744.Citation: Uppsala University (Sweden)
''Linnaeus' thermometer''
/ref> Working independently of Celsius, the
Lyon Lyon (Franco-Provençal: ''Liyon'') is a city in France. It is located at the confluence of the rivers Rhône and Saône, to the northwest of the French Alps, southeast of Paris, north of Marseille, southwest of Geneva, Switzerland, north ...
nais physicist
Jean-Pierre Christin Jean-Pierre Christin (31 May 1683 – 19 January 1755) was a French physicist, mathematician, astronomer, and musician. His proposal in 1743 to reverse the Celsius thermometer scale (from water boiling at 0 degrees and ice melting at 100 degree ...
, permanent secretary of the ''Académie des sciences, belles-lettres et arts de Lyon'' FR, developed a similar scale in which ''0'' represented the freezing point of water and ''100'' represented boiling. Don Rittner; Ronald A. Bailey (2005)
''Encyclopedia of Chemistry.''
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,
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,
New York City New York, often called New York City (NYC), is the most populous city in the United States, located at the southern tip of New York State on one of the world's largest natural harbors. The city comprises five boroughs, each coextensive w ...
. pp. 43.
On 19 May 1743 he published the design of a
mercury thermometer Mercury most commonly refers to: * Mercury (planet), the closest planet to the Sun * Mercury (element), a chemical element * Mercury (mythology), a Roman deity Mercury or The Mercury may also refer to: Companies * Mercury (toy manufacturer) ...
, the "Thermometer of Lyon" built by the craftsman Pierre Casati that used this scale.''
Mercure de France The () was originally a French gazette and literary magazine first published in the 17th century, but after several incarnations has evolved as a publisher, and is now part of the Éditions Gallimard publishing group. The gazette was publis ...
'' (1743)
''MEMOIRE sur la dilatation du Mercure dans le Thermométre.''
Chaubert; Jean de Nully, Pissot, Duchesne,
Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...
. pp. 1609–1610.
''Journal helvétique'' (1743)
''LION.''
Imprimerie des Journalistes,
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. pp. 308-310.
''Memoires pour L'Histoire des Sciences et des Beaux Arts'' (1743)
''DE LYON.''
Chaubert, París. pp. 2125-2128.
The medical thermometer was used by Dutch chemist and physician
Hermann Boerhaave Herman Boerhaave (, 31 December 1668 – 23 September 1738Underwood, E. Ashworth. "Boerhaave After Three Hundred Years." ''The British Medical Journal'' 4, no. 5634 (1968): 820–25. .) was a Dutch chemist, botanist, Christian humanist, and ph ...
(1668–1738), as well as his notable students
Gerard van Swieten Gerard van Swieten (7 May 1700 – 18 June 1772) was a Dutch physician who from 1745 was the personal physician of the Holy Roman Empress Maria Theresa and transformed the Austrian health service and medical university education. He was the f ...
(1700–72) and Anton de Haen (1704–76). It was also utilized around the same time by Scottish physician George Martine (1700–1741). De Haen made particular strides in medicine with the thermometer. By observing the correlation in a patient's change in temperature and the physical symptoms of the illness, he concluded that a record of one's temperature could inform the doctor of a patient's health. However, his proposals were not met with enthusiasm by his peers and the medical thermometer remained a scarcely used instrument in medicine. Thermometers remained cumbersome to transport and use. By the mid 19th century, the medical thermometer was still a foot long (30.28 cm) and took as long as twenty minutes to take an accurate temperature reading. Between 1866 and 1867, Sir Thomas Clifford Allbutt (1836–1925) designed a medical thermometer that was much more portable, measuring only six inches long and taking only five minutes to record a patient's temperature. In 1868, German physician, pioneer psychiatrist, and medical professor Carl Reinhold August Wunderlich published his studies that consisted of over one million readings from twenty-five thousand patients' temperatures, taken in the
underarm The axilla (: axillae or axillas; also known as the armpit, underarm or oxter) is the area on the human body directly under the shoulder joint. It includes the axillary space, an anatomical space within the shoulder girdle between the arm and ...
. With his findings, he was able to conclude a healthy human's temperature fell within the range of 36.3 to 37.5 °C (97.34 to 99.5 °F). Dr. Theodor H. Benzinger (13 April 1905 - 26 October 1999) invented the ear thermometer in 1964. Born in
Stuttgart Stuttgart (; ; Swabian German, Swabian: ; Alemannic German, Alemannic: ; Italian language, Italian: ; ) is the capital city, capital and List of cities in Baden-Württemberg by population, largest city of the States of Germany, German state of ...
, Germany, he immigrated to the U.S. in 1947 and became a
naturalized citizen Naturalization (or naturalisation) is the legal act or process by which a non-national of a country acquires the nationality of that country after birth. The definition of naturalization by the International Organization for Migration of the ...
in 1955. He worked from 1947 to 1970 in the
bioenergetics Bioenergetics is a field in biochemistry and cell biology that concerns energy flow through living systems. This is an active area of biological research that includes the study of the transformation of energy in living organisms and the study o ...
division at the Naval Medical Research Center in Bethesda, Maryland.


Classification by location

The temperature can be measured in various locations on the body which maintain a fairly stable temperature (mainly oral, axillary, rectal, tympanic, or temporal). The normal temperature varies slightly with the location; an oral reading of 37 °C does not correspond to rectal, temporal, etc. readings of the same value. When a temperature is quoted the location should also be specified. If a temperature is stated without qualification (e.g., typical body temperature) it is usually assumed to be sub-lingual. The differences between core temperature and measurements at different locations, known as ''clinical bias'', is discussed in the article on
normal human body temperature Normal human body temperature (normothermia, euthermia) is the typical temperature range found in humans. The normal human body temperature range is typically stated as . Human body temperature varies. It depends on sex, age, time of day, exer ...
. Measurements are subject to both site-dependent clinical bias and variability between a series of measurements (
standard deviation In statistics, the standard deviation is a measure of the amount of variation of the values of a variable about its Expected value, mean. A low standard Deviation (statistics), deviation indicates that the values tend to be close to the mean ( ...
s of the differences). For example, one study found that the clinical bias of rectal temperatures was greater than for ear temperature measured by a selection of thermometers under test, but variability was less.


Oral

Oral temperature may only be taken from a patient who is capable of holding the thermometer securely under the tongue, which generally excludes small children or people who are unconscious or overcome by coughing, weakness, or vomiting. (This is less of a problem with fast-reacting digital thermometers, but is certainly an issue with mercury thermometers, which take several minutes to stabilise their reading.) If the patient has drunk a hot or cold liquid beforehand time must be allowed for the mouth temperature to return to its normal value. The typical range of a sub-lingual thermometer for use in humans is from about 35 °C to 42 °C or 90 °F to 110 °F.


Armpit

The armpit (
axilla The axilla (: axillae or axillas; also known as the armpit, underarm or oxter) is the area on the human body directly under the shoulder joint. It includes the axillary space, an anatomical space within the shoulder girdle between the arm a ...
) temperature is measured by holding the thermometer tightly under the armpit. One needs to hold the thermometer for several minutes to get an accurate measurement. The axillary temperature plus 1 °C is a good guide to the rectal temperature in patients older than 1 month. The accuracy from the axilla is known to be inferior to the rectal temperature.


Rectal

Rectal thermometer temperature-taking, especially if performed by a person other than the patient, should be facilitated with the use of a water-based personal lubricant. Although rectal temperature is the most accurate, this method may be considered unpleasant or embarrassing; in 1966,
Time Magazine ''Time'' (stylized in all caps as ''TIME'') is an American news magazine based in New York City. It was published weekly for nearly a century. Starting in March 2020, it transitioned to every other week. It was first published in New York Cit ...
noted "what for many remains a humiliating procedure ... insertion of a rectal thermometer." Also, if not taken the correct way, rectal temperature-taking can be uncomfortable and in some cases painful for the patient. Rectal temperature-taking is considered the method of choice for
infant In common terminology, a baby is the very young offspring of adult human beings, while infant (from the Latin word ''infans'', meaning 'baby' or 'child') is a formal or specialised synonym. The terms may also be used to refer to juveniles of ...
s.


Ear

The ear thermometer was invented by Dr. Theodor H. Benzinger in 1964. At the time, he was seeking a way to get a reading as close to the brain's temperature as possible, since the
hypothalamus The hypothalamus (: hypothalami; ) is a small part of the vertebrate brain that contains a number of nucleus (neuroanatomy), nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrin ...
at the brain's base regulates the core body temperature. He accomplished this by using the ear canal's
ear drum In the anatomy of humans and various other tetrapods, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear from the middle ear. Its function is to transmit changes in pressur ...
's
blood vessels Blood vessels are the tubular structures of a circulatory system that transport blood throughout many animals’ bodies. Blood vessels transport blood cells, nutrients, and oxygen to most of the tissues of a body. They also take waste an ...
, which are shared with the hypothalamus. Before the ear thermometer's invention, easy temperature readings could only be taken from the mouth, rectum, or
underarm The axilla (: axillae or axillas; also known as the armpit, underarm or oxter) is the area on the human body directly under the shoulder joint. It includes the axillary space, an anatomical space within the shoulder girdle between the arm and ...
. Previously, if doctors wanted to record an accurate brain temperature, electrodes needed to be attached to the patient's hypothalamus. This tympanic thermometer has a projection (protected by a one-time hygienic sheath) that contains the infrared probe; the projection is gently placed in the ear canal and a button pressed; the temperature is read and displayed within about a second. These thermometers are used both in the home and in medical facilities. There are factors that make readings of this thermometer to some extent unreliable, for example faulty placement in the external ear canal by the operator, and wax blocking the canal. Such error-producing factors usually cause readings to be below the true value, so that a fever can fail to be detected.


Forehead


Temporal artery

Temporal artery thermometers, which use the infrared principle report temperature, are becoming increasingly common in clinical practice because of their ease of use and minimal invasiveness. Because of the variability of technique and environmental considerations, measurements by temporal artery thermometers may suffer issues of precision, and to a lesser degree
accuracy Accuracy and precision are two measures of ''observational error''. ''Accuracy'' is how close a given set of measurements (observations or readings) are to their ''true value''. ''Precision'' is how close the measurements are to each other. The ...
. Temporal thermometers have been found to have a low sensitivity of around 60–70%, but a very high specificity of 97–100% for detecting fever and hypothermia. Because of this, it is suggested that they should not be used in acute care settings like the ICU, or in patients with a high suspicion of temperature imbalance. Evidence supports higher accuracy and precision amongst pediatric patients.


Plastic strip thermometer

The thermometer is applied to the patient's brow. It is typically a band coated with different temperature-sensitive markings using plastic strip thermometer or similar technology; at a given temperature the markings (numerals indicating the temperature) in one region are at the right temperature to become visible. This type may give an indication of fever, but is not considered accurate.


Classification by technology


Liquid-filled

The traditional thermometer is a glass tube with a bulb at one end containing a liquid which expands in a uniform manner with temperature. The tube itself is narrow (capillary) and has calibration markings along it. The liquid is often mercury, but alcohol thermometers use a colored alcohol. Medically, a maximum thermometer is often used, which indicates the maximum temperature reached even after it is removed from the body. To use the thermometer, the bulb is placed in the location where the temperature is to be measured and left long enough to be certain to reach
thermal equilibrium Two physical systems are in thermal equilibrium if there is no net flow of thermal energy between them when they are connected by a path permeable to heat. Thermal equilibrium obeys the zeroth law of thermodynamics. A system is said to be in t ...
—typically five minutes in the mouth and ten minutes under the armpit. Maximum-reading is achieved by means of a constriction in the neck close to the bulb. As the temperature of the bulb rises, the liquid expands up the tube through the constriction. When the temperature falls, the column of liquid breaks at the constriction and cannot return to the bulb, thus remaining stationary in the tube. After reading the value, the thermometer must be reset by repeatedly swinging it sharply to shake the liquid back through the constriction.


Mercury

Mercury-in-glass thermometers have been considered the most accurate liquid-filled types. However, mercury is a toxic heavy metal, and mercury has only been used in clinical thermometers if protected from breakage of the tube. The tube must be very narrow to minimise the amount of mercury in it—the temperature of the tube is not controlled, so it must contain very much less mercury than the bulb to minimise the effect of the temperature of the tube—and this makes the reading rather difficult as the narrow mercury column is not very visible. Visibility is less of a problem with a coloured liquid. It has been decided by many states to prohibit the use and sale of mercury thermometers due to the risk of handling and spilling, and the potential to cause
mercury poisoning Mercury poisoning is a type of metal poisoning due to exposure to mercury. Symptoms depend upon the type, dose, method, and duration of exposure. They may include muscle weakness, poor coordination, numbness in the hands and feet, skin rashe ...
; the vigorous swinging needed to "reset" a mercury maximum thermometer makes it easy to accidentally break it and release poisonous mercury vapors. Mercury thermometers have largely been replaced by electronic digital thermometers, or, more rarely, thermometers based on liquids other than mercury (such as
galinstan Galinstan is a brand name for an alloy composed of gallium, indium, and tin which melts at and is thus liquid at room temperature. In scientific literature, galinstan is also used to denote the eutectic alloy of gallium, indium, and tin, which ...
, coloured
alcohol Alcohol may refer to: Common uses * Alcohol (chemistry), a class of compounds * Ethanol, one of several alcohols, commonly known as alcohol in everyday life ** Alcohol (drug), intoxicant found in alcoholic beverages ** Alcoholic beverage, an alco ...
s and heat-sensitive liquid crystals).


Gallium

One company markets a thermometer of this sort which it bills as "the first analogue thermometer without mercury," as it instead uses the
liquid metal A liquid metal is a metal or a metal alloy which is liquid at or near room temperature. The only stable liquid elemental metal at room temperature is Mercury (element), mercury (Hg), which is molten above −38.8 °C (234.3 K, −37.9  ...
gallium Gallium is a chemical element; it has Chemical symbol, symbol Ga and atomic number 31. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875, elemental gallium is a soft, silvery metal at standard temperature and pressure. ...
. Gallium is considered non-toxic and when disposed of does not face environmental concerns. Like mercury, gallium is a liquid at body temperature (melting point 29.7 °C), but according to the manufacturer an alloy of gallium, indium and tin is actually used, resulting in a lower melting temperature.


Phase-change (dot matrix) thermometers

Phase-change thermometers use samples of inert chemicals which melt at progressively higher temperatures from 35.5 °C to 40.5 °C in steps of 0.1 °C. They are mounted as small dots in a matrix on a thin plastic spatula with a protective transparent cover. This is placed under the patient's tongue. After a short time the spatula is removed and it can be seen which dots have melted and which have not: the temperature is taken as the melting temperature of the last dot to melt. These are cheap disposable devices and avoid the need for sterilizing for re-use.


Liquid crystal

A
liquid crystal thermometer A liquid crystal thermometer, temperature strip or plastic strip thermometer is a type of thermometer that contains heat-sensitive (thermochromic) liquid crystals in a plastic strip that change colour to indicate different temperatures. Liquid cr ...
contains heat-sensitive (
thermochromic Thermochromism is the property of Chemical substance, substances to change color due to a change in temperature. A mood ring is an example of this property used in a consumer product although thermochromism also has more practical uses, such as b ...
) liquid crystals in a plastic strip that change color to indicate different temperatures.


Electronic

Since compact and inexpensive methods of measuring and displaying temperature became available, electronic thermometers (often called ''digital'', because they display numeric values) have been used. Many display readings with a resolution of only 0.1 °C (.2 °F), but this should not be taken as a guarantee of accuracy: the specified accuracy must be checked in the documentation and maintained by periodic recalibration. A typical inexpensive electronic ear thermometer for home use has a displayed resolution of 0.1 °C, but a stated accuracy within ±0.2 °C (±0.35 °F) when new. The first electronic clinical thermometer, invented in 1954, used a flexible probe that contained a Carboloy thermistor.


Types of Digital Thermometer


=Resistance temperature detectors (RTDs)

= RTDs are wire windings or other thin film serpentines that exhibit changes in resistance with changes in temperature. They measure temperature using the positive temperature coefficient of electrical resistance of metals. The hotter they become, the higher the value of their electrical resistance. Platinum is the most commonly used material because it is nearly linear over a wide range of temperatures, is very accurate, and has a fast response time. RTDs can also be made of copper or nickel. Advantages of RTDs include their stable output for long periods of time. They are also easy to calibrate and provide very accurate readings. Disadvantages include a smaller overall temperature range, higher initial cost, and a less rugged design


=Thermocouples

= Thermocouples are accurate, highly sensitive to small temperature changes, and quickly respond to changes to the environment. They consist of a pair of dissimilar metal wires joined at one end. The metal pair generates a net thermoelectric voltage between their opening and according to the size of the temperature difference between the ends. •Advantages of thermocouples include their high accuracy and reliable operation over an extremely wide range of temperatures. They are also well-suited for making automated measurements both inexpensive and durable. •Disadvantages include errors caused by their use over an extended period of time, and that two temperatures are required to make measurements. Thermocouple materials are subject to corrosion, which can affect the thermoelectric voltage


=Thermistor

= Thermistor elements are the most sensitive temperature sensors available. A thermistor is a semiconductor device with an electrical resistance that is proportional to temperature. There are two types of products. •Negative temperature coefficient (NTC) devices are used in temperature sensing and are the most common type of thermistor. NTCs have temperatures that vary inversely with their resistance, so that when the temperature increases, the resistance decreases, and vice versa. NTCs are constructed from oxides of materials such as nickel, copper, and iron. • Positive temperature coefficient (PTC) devices are used in electric current control. They function in an opposite manner than NTC in that the resistance increases as temperature increases. PTCs are constructed from thermally sensitive silicons or polycrystalline ceramic materials. • There are several advantage and disadvantages to using an NTC thermistor thermometer. • Advantages include their small size and high degree of stability. NTCs are also long lasting and very accurate. • Disadvantages include their non-linearity, and unsuitability for use in extreme temperatures


Contact

Some electronic thermometers may work by contact (the electronic sensor is placed in the location where temperature is to be measured, and left long enough to reach equilibrium). These typically reach equilibrium faster than mercury thermometers; the thermometer may beep when equilibrium has been reached, or the time may be specified in the manufacturer's documentation.


Remote

Other electronic thermometers work by remote sensing: an infrared sensor responds to the radiation
spectrum A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...
emitted from the location. Although these are not in direct contact with the area being measured, they may still contact part of the body (a thermometer which senses the temperature of the eardrum without touching it is inserted into the ear canal). To eliminate the risk of patient cross-infection, disposable probe covers and single-use clinical thermometers of all types are used in clinics and hospitals.


Accuracy

According to a 2001 research, electronic thermometers on the market significantly underestimate higher temperatures and overestimate lower temperatures. The researchers conclude that "the current generation of electronic, digital clinical thermometers, in general, may not be sufficiently accurate or reliable to replace the traditional glass/mercury thermometers""An investigation into the accuracy of different types of thermometers"
''Nursing Times.net'', 1 October 2002.


Basal thermometer

A basal thermometer is a
thermometer A thermometer is a device that measures temperature (the hotness or coldness of an object) or temperature gradient (the rates of change of temperature in space). A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb ...
used to take the basal (base) body temperature, the temperature upon waking.
Basal body temperature Basal body temperature (BBT or BTP) is the lowest body temperature attained during rest (usually during sleep). It is usually estimated by a temperature measurement immediately after awakening and before any physical activity has been undertaken. ...
is much less affected than daytime temperature by environmental factors such as exercise and food intake. This allows small changes in body temperature to be detected Glass oral thermometers typically have markings every 0.1 °C or 0.2 °F. Basal temperature is stable enough to require accuracy of at least 0.05 °C or 0.1 °F, so special glass basal thermometers are distinct from glass oral thermometers. Digital thermometers which have sufficient resolution (0.05 °C or 0.1 °F is sufficient) may be suitable for monitoring basal body temperatures; the specification should be checked to ensure absolute accuracy, and thermometers (like most digital instruments) should be calibrated at specified intervals. If only the variation of basal temperature is required, absolute accuracy is not so important so long as the readings do not have large variability (e.g., if real temperature varies from 37.00 °C to 37.28 °C, a thermometer which inaccurately but consistently reads a change from 37.17 °C to 37.45 °C will indicate the magnitude of the change). Some digital thermometers are marketed as "basal thermometers" and have extra features such as a larger display, expanded memory functions, or beeping to confirm the thermometer is placed properly.


Smart and wearable thermometers

A smart thermometer is able to transmit its readings so that they can be collected, stored and analysed. Wearable thermometers can provide continuous measurement but it is difficult to measure core body temperature in this way.


See also

*
Thermometer A thermometer is a device that measures temperature (the hotness or coldness of an object) or temperature gradient (the rates of change of temperature in space). A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb ...
*
Liquid crystal thermometer A liquid crystal thermometer, temperature strip or plastic strip thermometer is a type of thermometer that contains heat-sensitive (thermochromic) liquid crystals in a plastic strip that change colour to indicate different temperatures. Liquid cr ...


Footnotes


References

Allbutt, T.C., "Medical Thermometry", ''British and Foreign Medico-Chirurgical Review''
Vol.45, No.90, (April 1870), pp.429-441Vo.46, No.91, (July 1870), pp.144-156.
{{DEFAULTSORT:Medical Thermometer Medical testing equipment Thermometers Italian inventions