The word „thermometer“ is of French origin and was first used in 1624. in a French mathematics text. The first modern thermometer, completely closed-ended and containing alcohol, was produced by the Grand Duke de'Medici of Tuscany about 20 years later. Measuring the temperature with such a thermometer would take 20 minutes. in 1866 Sir Thomas Allbutt developed a clinical thermometer that could take a temperature in 5 minutes.

Thermometers used to measure body temperature are called medical thermometers. They measure a person's body temperature by inserting the tip into the mouth (oral), armpit (armpit), or rectum (rectal). Traditionally, mercury thermometers were used in the same way as air thermometers. As liquid mercury is heated in the nozzle, it will expand into the thermometer tube, fluctuating with temperature and stopping at a point on the scale. The thermometer scale was debated until Daniel Fahrenheit created the Fahrenheit scale, nearly 100 years after the invention of the air thermometer. The Fahrenheit scale was developed using mercury as a liquid in glass tubes, which was to become the standard until the 1990s, when digital thermometers began to replace traditional thermometers in medicine due to safety concerns.

Another type of thermometer used to measure body temperature is called a basal thermometer. These devices measure your core body temperature when you wake up. This is the most effective way to eliminate environmental factors related to body temperature, such as exercise or diet. Changes in basal body temperature are used to determine fertility and ovulation in women trying to get pregnant. Most medical mercury thermometers have a sensitivity of 0.2 degrees, basal body temperature fluctuations require a sensitivity of 0.1 degrees. Most digital thermometers are sensitive enough to measure basal temperature as well.

Having a reliable medical thermometer at home can be incredibly helpful. Being able to accurately tell if someone has a fever gives you much-needed information about important next steps in their care.

There are many types of contact and non-contact thermometers to choose from. The ages of your household members and personal preferences can help you decide which types to buy.

Like any other appliance in your home, it's important to understand how your thermometer works. Not every type works the same or is designed to give the same temperature reading.

Guesswork is the last thing you want to rely on when someone is sick. Here's an overview of medical thermometers, how to use them, and what their readings mean.

Types of medical thermometers

No matter which type you choose, read the manufacturer's instructions carefully. No thermometer will give accurate results if used incorrectly. Never use a human thermometer intended for other purposes, such as a laboratory or meat thermometer. It will not give an accurate reading.

If you're a parent, you might be wondering why we're not including forehead strip thermometers from this review. Strip thermometers are inexpensive and quick to use. However, since they measure skin temperature rather than body temperature, they are much less accurate and should be avoided.

Digital thermometers. Digital thermometers work by using heat sensors that detect body temperature. They can be used to measure temperature in the mouth, rectum or armpit. When evaluating digital thermometer readings, remember that the axilla (armpit) temperature is about 0.6°F (0.6°C) cooler than the oral temperature. Rectal thermometers run 0.6°F (0.6°C) warmer than oral thermometers.

Advantages. Digital thermometers provide accurate readings in about 1 minute or less.

Disadvantages. To get an accurate reading when measuring in the mouth, the tip of the device must be completely closed under the tongue. For this reason, rectal readings for infants and young children are considered the most accurate.

You should not use the same thermometer for both rectal and oral readings. This may require the purchase of two thermometers, which should be labeled.

Thermometer batteries need to be changed periodically. Make sure you have the right type of batteries for your device on hand and know how to replace them.

Oral thermometers

Oral temperature can be measured with a digital or mercury thermometer. The average oral temperature is 98.6°F (37°C). However, any oral temperature between 97°F (36.1°C) and 99°F (37.2°C) is considered normal. Some people's normal body temperature is slightly lower, others slightly higher. Therefore, it is useful to know what your normal body temperature is so that you can assess whether you have a fever when you feel unwell.

Advantages. Oral thermometers are most accurate for children over 3 years of age and adults.

Disadvantages. Young children and people with breathing problems may not be able to hold the thermometer in their mouth long enough to get an accurate reading.

How to measure temperature. To measure the temperature with a digital oral thermometer, first wash your hands. Then make sure your thermometer is clean and has working batteries. Turn on the thermometer and place the plastic wrap over the bottom end of the thermometer. The thermometer will indicate that it is ready for use with a sound, light or both signals. Place the tip of the thermometer under the tongue. Some thermometers have grooves that indicate how far into the mouth it should go. Keep your mouth closed until you hear a beep or similar sound. Remove the thermometer and look at the reading. Clean the thermometer between uses according to the manufacturer's instructions, even if only one person is using it.

Digital ear (drum) thermometer

Ear (drum) thermometers measure the temperature inside the ear canal using infrared technology. These thermometers read 0.5°F (0.3°C) to 1°F (0.6°C) higher than oral thermometers.

Advantages. Ear (tympanic) thermometers provide fast and accurate readings and may be superior to oral or rectal thermometers, especially in children.

Disadvantages. Due to the size of the ear canal, ear thermometers are not recommended for babies under 6 months of age. They must be placed correctly for accurate results. However, they may not fit properly in a small or curved ear canal. Also, obstructions such as earwax can distort the results.

Digital forehead thermometer

Forehead thermometers use infrared sensors to measure the temperature of the superficial forehead artery, which is a branch of the carotid artery. Some are known as non-contact infrared thermometers.

Forehead thermometers, which do not require physical contact, have become very popular for use in places such as airports, stores and stadiums.

Forehead temperature readings are approximately 1°F (0.6°C) lower than oral temperature readings.

Advantages. Forehead thermometers allow you to quickly determine body temperature in just a few seconds. They are easy to administer and can be used in infants, children and adults.

Disadvantages. Forehead thermometers must be attached accurately and according to the manufacturer's instructions, otherwise they will not give a correct reading. Readings can be affected by external factors including drafts, wind, room heating and direct sunlight. Wearing certain clothing, such as hats or heavy coats, may distort the results.

How to measure forehead temperature using non-contact forehead probe the thermometer. Non-contact forehead thermometers usually have a removable cover to keep it clean. Be sure to remove the cap before use. Turn on the device with the power button. You'll know it's on if it lights up and the boot sequence loads. When the thermometer is ready, place it no more than 2 inches from the center of the forehead. With some models, you can also touch the forehead. In any case, you will get the most accurate reading possible if your forehead is clean and free of hair. Be sure to hold the thermometer steady. To get an accurate reading, the thermometer and forehead must be stationary. Press the temperature button. The device will beep or flash to indicate that the thermometer is ready to read the temperature. It will only take about 2 seconds.

Instructions for forehead thermometers vary by manufacturer, so be sure to read and keep the instructions or user manual with the device.

Pacifier thermometer

If your baby uses a pacifier, this can be an easy way to record their approximate temperature.

Advantages. Ease of use is the biggest advantage of pacifier thermometers.

Disadvantages. Pacifier thermometers should remain in the mouth without moving for up to 6 minutes. Also, they give an approximate temperature rather than an exact reading.

Mercury thermometer

Mercury thermometers were once the only way to measure temperature. They are no longer widely used for security reasons.

Advantages. Mercury thermometers provide accurate temperature readings and can be used orally, rectally, or in the armpit. They don't need batteries.

Disadvantages. Because they are made of glass, mercury thermometers can break easily, allowing toxic mercury to escape. They can also cut when broken. Because they contain hazardous materials, mercury thermometers must be disposed of properly and cannot be thrown in the trash. It is difficult for older people to see the readings in them and to get an accurate body temperature these thermometers need to be held for 3 minutes.

Smart thermometers

This thermometer consists of a temperature sensor and an associated mobile application. The temperature sensor allows continuous and accurate monitoring of temperature changes. All collected measurements are sent to the mobile application, where the results are presented both graphically and numerically with even two decimal places. In addition, the application can provide the highest and average temperature. The smart thermometer is intended for users over 3 years of age.

Advantages. It's a thermometer that increases comfort for parents of children with chronic illnesses. Night temperature measurements do not interfere with rest and therefore provide a better feeling of well-being during the day. It is also a good solution for seniors with chronic diseases. The results are automatically recorded and archived in the app. The system reports a sudden rise in temperature. The long-lasting battery allows you not to worry about cyclic charging of the device.

Disadvantages. App-based thermometers can be significantly more expensive than digital thermometers without Bluetooth connectivity.

What type of thermometer is most accurate?

The best thermometer is the one that you can use most conveniently and correctly. It is also important whether the thermometer is from a reliable manufacturer.

Many medical professionals still consider rectal thermometers to be the gold standard for infants and children. However, oral and forehead thermometer readings are also very reliable in these age groups.

Always remember that temperature readings vary depending on how the thermometer is inserted:

A rectal thermometer reading will be approximately 0.5°F (0.3°C) to 1°F (0.6°C) higher than an oral temperature reading.

Ear thermometer readings are usually 0.5°F (0.3°C) to 1°F (0.6°C) higher than oral temperature readings.

Axillary thermometer readings can be 0.5°F (0.3°C) to 1°F (0.6°C) lower than oral temperature readings (and may be the least reliable).

Forehead thermometer readings are often 0.5°F (0.3°C) to 1°F (0.6°C) lower than temperature readings.

How to choose the right thermometer?

The first thing to consider is how you intend to use it. Some thermometers are designed for babies or children, while others are better for adults.

Then decide whether you prefer an oral, ear, forehead or non-contact thermometer. For example, if you tend to build up earwax, an ear thermometer is probably not a good choice. Glass thermometers, which can break, or mercury thermometers, which are dangerous, should be avoided.

Here are some other things to consider when choosing a thermometer:

Accuracy. The purpose of a thermometer is to measure body temperature. Everything else is a bonus, and paying more doesn't necessarily get you any accuracy. Fever strips and pacifier thermometers are known to be inaccurate because they only show approximate temperatures.

Ease of use. Can you easily remove or insert the thermometer and it gives a reading within minutes? Is it easy to manage or does it require too many steps? If it seems too complicated or inconvenient, it probably is.

Look for things that matter to you:

Do you need a large, easy-to-read screen?

Would a flexible nozzle be better for your kids?

Do you want a loud beep or the ability to turn it off?

Would it be useful to have a lot of memory?

Or do you want your body temperature to be constantly monitored?

Choose the one that meets your essential requirements.

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https://www.healthline.com/health/best-thermometer#our-picks

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