What do thermometers actually detect

Wait at least 1 hour after heavy exercise or a hot bath before measuring body temperature. Wait for 20 to 30 minutes after smoking, eating, or drinking a hot or cold liquid. The average normal body temperature is The normal temperature can vary due to things such as:. You need to have an accurate temperature measurement to determine if a fever is present. Be sure to tell your health care provider which type of temperature measurement you used when discussing a fever.

The exact relationship between different types of temperature measurement is unclear. However, the following general guidelines for temperature results are used:. If the reading on the thermometer is more than 1 to 1. Fevers may be a sign of:. Body temperature that is too high or too low can be serious. Call your provider if this is the case. Vital signs measurement. Philadelphia, PA: Elsevier; chap 1. Temperature regulation and the pathogenesis of fever. Philadelphia, PA: Elsevier; chap Fever: pathogenesis and treatment.

Pacifier thermometers must remain in the mouth, without moving, for up to 6 minutes. Additionally, they provide an approximation of temperature rather than an exact reading. The best thermometer is the one that you can use most comfortably and correctly.

Rectal thermometers are still considered by many medical professionals to be the gold standard for babies and children. However, oral and forehead readings are also typically very reliable in these age groups. Always keep in mind that temperature readings vary, based on how the thermometer is administered:.

If your child is squirming, it may be hard to get an accurate reading. If so, remove the thermometer and use a different thermometer to take an oral, armpit, or forehead reading. No-touch forehead thermometers usually have a removable cap that keeps it clean during storage.

Make sure you take the cap off before use. Digital thermometers are a popular option, which can be used orally, rectally, or under the armpit. There are some no-touch forehead thermometers that are also popular, especially in social settings. Digital thermometers are the most accurate way to take body temperature. There are many types, including oral, rectal, and forehead, plus many that…. When should you break a fever, and when should you let it run its course?

Here's everything you need to know about when and how to break a fever. Because most people from that time period were not too concerned about the temperature of ice and salt, this scale was destined for the dustbin of history.

Daniel Gabriel Fahrenheit, a German physicist, published an alternate scale in It is unclear whether Romer also used ammonium chloride in his experiments, as many of his records were destroyed in a fire. Each degree of his scale corresponded to one ten-thousandth the initial volume of mercury used in his thermometer. To this day, there is considerable controversy as to how Fahrenheit actually arrived at his temperature scale. He never did reveal exactly how he arrived at the reference points for his thermometer, as he did not want others to construct and sell the thermometers he had spent much of his life perfecting.

Whether these points were intentionally chosen to represent these extremes or just happened to work out this way is still being debated today. This was an issue not so much with the general public, but rather with scientists, who tend to obsess over such things. However, others have postulated that placing degrees between the freezing and boiling points of water was not arbitrary but quite rational, as this number represents the number of degrees in half a circle.

Hence, it was termed the Centigrade scale, since the prefix centi- represents onehundredth. This was later reversed after his death. Most countries that have adopted the metric system of measurement use this temperature scale, as it is conveniently broken down into units of In , the Centigrade scale was officially designated the Celsius scale, although some people still use the outdated term. The most scientific scale in use today is the Kelvin, or absolute, temperature scale.

Because temperature is a measure of molecular motion, it only makes sense that the zero point of your scale should be the point where molecular motion stops.

That is exactly what the Kelvin scale accomplishes. In at MIT, scientists came very close to reaching absolute zero, obtaining a frosty temperature of 4. The Kelvin scale is primarily used in science, and temperature must be expressed in Kelvin when solving many equations involving temperature, such as the gas laws. But it tends to be too cumbersome for everyday use, since the freezing point of water is K and the boiling point is K.

The first thermometer in modern times was a crude water thermometer believed to have been invented by Galileo Galilei in Many of these first thermometers used wine, as its alcohol content prevented it from freezing and its red color made it easy to read. However, these first thermometers were very sensitive to air pressure, and functioned as much as a barometeras they did as a thermometer. So eventually, all thermometers were constructed of a sealed glass tube that had all the air removed.

Because these vacuum tubes were shut off from the outside atmosphere, changes in air pressure would not affect the temperature reading. In , Fahrenheit invented the alcohol thermometer, and in , he invented the first mercury thermometer.

All thermometers work according to the same basic principle: objects expand when heated and contract when cooled. The most common thermometer is the bulb thermometer, which comprises a large bulb filled with a liquid and a narrow glass tube through which the liquid rises. Mercury was the liquid of choice for many years, because it expands and contracts at a very constant rate, making mercury thermometers very accurate. However, because of concerns about mercury toxicity, mercury has often been replaced with alcohol that is colored red.

Mercury has a silver color. Another very common type of thermometer is the bimetallic strip thermometer. For information on user permissions, please read our Terms of Service. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher. They will best know the preferred format. When you reach out to them, you will need the page title, URL, and the date you accessed the resource.

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Thermodynamics is a branch of physics that studies heat transfer between systems. This field has observed the laws of thermodynamics which define how heat, within a system, flows and does work. In any system, when two objects with different temperatures are brought into contact with one another, they will eventually establish thermodynamic equilibrium.

As heat moves from one object to the other, physical changes will take place: the balloon filled with gas will grow or shrink, the roadway will expand or contract, the electrical resistance in the circuit will increase or decrease, and these changes are predictable and can be measured. Engineers and scientists take these laws into account when they design projects and experiments. Use these resources to learn more about thermodynamics. Join our community of educators and receive the latest information on National Geographic's resources for you and your students.

Skip to content. Twitter Facebook Pinterest Google Classroom. Encyclopedic Entry Vocabulary. A thermometer is an instrument that measures temperature.

It can measure the temperature of a solid such as food , a liquid such as water, or a gas such as air. The three most common units of measurement for temperature are Celsius, Fahrenheit, and kelvin. The Celsius scale is part of the metric system.

The metric system of measurement also includes units of mass , such as kilograms, and units of length, such as kilometers. The metric system, including Celsius, is the official system of measurement for almost all countries in the world.