Thermometers: A Complete Guide

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Thermometers: Introduction

From influencing seasonal changes to indicating inflammation, temperature measurements matter. Hence, it’s not surprising that thermometers are invaluable in numerous areas, such as medicine, ecology, laboratory research, food preparation, and industrial settings. Note that thermometers are defined as versatile meters used to measure temperature or the average thermal energy of a system.

Interestingly, the earliest thermometers were called thermoscopes. It was Galileo Galilei, who drove the use of thermoscopes forward; his open tube device filled with liquid and glass bulbs designed in 1593 is still considered an iconic invention. The first thermoscopes, however, didn’t show any numerical values and were hard to read. Note that in 1612, the Venetian physiologist Santorio Santorio developed the first numerical scale applied to thermoscopes, whereas in 1654, Ferdinando II de Medici created the first sealed glass tube meter. The earliest modern thermometer was invented in 1709 by the notable physicist Daniel Fahrenheit who assigned different temperatures for the boiling and freezing points of water (at 212 degrees and 32 degrees, respectively).

Enhanced by the advancements in science and technology, the design of today’s thermometers is highly sophisticated. Modern thermometers are based on various thermometric techniques (for example, liquid crystal methods), with infrared thermometers (also known as laser or non-contact thermometers) being highly popular units.


Thermometers & Scales

Despite the evolution of thermometers over the years, some of the numerical temperature scales developed in the 18th century are still in use, particularly the Fahrenheit and Celsius scales. Interestingly, by the 1700s, more than 35 scales had been designed. Daniel Fahrenheit, as stated earlier, assigned the boiling point of water at 212 degrees and the freezing point at 32 degrees; whereas the Swedish physicist, Anders Celsius developed the first centigrade scale in 1742 and assigned the boiling point of water at 0 degrees and the melting point of snow at 100 degrees. Now the Celsius scale is highly popular across the world, with 0 degrees being on the cold end and 100 degrees on the hot end. Interestingly, Fahrenheit and Celsius are equal at -40 degrees.

Other popular scales are the Kelvin and Rankine scales. In 1848, the British inventor William Thomson (known as Lord Kelvin) proposed a scale that used the Celsius scale but was keyed to absolute zero (-273.15°C). The Rankine scale invented by the Scottish engineer William Rankine, on the other hand, used the Fahrenheit scale, also keyed to absolute zero (-459.67°F). Note that absolute zero is the coldest theoretical temperature when substances do not possess any heat energy.


Types of Thermometers and Applications

The rapid technological advancement across the globe post-WWII fostered the production of advanced thermometers suitable for different applications. Some of the most common uses are:

Medical settings: Medical thermometers, including pet temperature meters, are among the most popular units on the market. We should mention that the first medical thermometer was invented by the English physician Sir Thomas Allbut in 1867. Today, there are different ear, forehead, underarm, oral, and rectal thermometers, all based on different thermometric technology, such as infrared, mercury-in-glass, plastic strip, and liquid crystal techniques. Note that in the past, the liquid used in glass units was almost always mercury, which can be highly harmful. When it comes to safety and temperature measurements, pacifier thermometers are suitable for infants, while disposable units are ideal for professional medical settings.

Food safety: Thermometers are invaluable in food safety to monitor refrigeration systems and cooking in order to prevent food-borne illnesses, bacterial growth, and overcooking. Note that some units utilize bimetallic coils, while others have thermistors with digital readouts. Interestingly, candy thermometers (used to achieve accurate water levels in sugar solutions) and temperature indicator labels (described as self-adhesive temperature proofing foils used in food safety, brewery, and sterilization) are also essential tools.

Environmental applications: Thermometers are often utilized to monitor indoor-outdoor temperatures and heat flow. From thermostats to alcohol thermometers, measuring temperature is invaluable in meteorology, weather forecasting, traffic monitoring, and aircraft engineering. Indoor thermometers are also essential in HVAC and climate control systems. Note that today’s technology allows temperatures to be mapped via thermography and continuous temperature measurements to be saved or shown in real-time via temperature data loggers.

Home use: Tracking temperature changes at home is essential to ensure one’s health and thermal comfort. Note that analog models are among the most affordable and popular models suitable for non-specialist settings. That being said, digital meters with easy-to-read data and advanced settings (humidity meters, clocks, etc.) are slowly replacing analog models.

Laboratory research: Lab thermometers have different applications and often include liquid-in-glass meters, infrared units, bimetallic strips, thermistors, and constant-volume gas models. Interestingly, probe thermometers (both fixed and wired probes) are invaluable in measuring liquids and semi-solid samples, while k-type thermocouples are among the most specialized meters used for extreme temperatures. Infrared thermometers, on the other hand, are ideal for non-contact measurements of extremely high or low surface temperatures.

Industrial settings: Additionally, there are precise temperature sensors and thermistors, including Fiber Bragg grating temperature sensors, employed in engineering systems, automotive trade, and industrial settings. Thermocouples and magnetic thermometers, for instance, are among the most utilized meters. Here we should mention that thermal imaging cameras are also popular units in industrial settings. Although such devices are not considered thermometers, they can indicate hot and cold areas via thermal imagery and indicate leaks and other damage. Nanothermometry and cryometry are also emerging in professional settings.


Choosing a Thermometer: Factors to Consider

Although there are different thermometers, applications, and measuring techniques to choose from, the three most important factors prospective buyers should consider are:

  • Requirements
  • Specifications
  • Total costs

Requirements: Prospective buyers should decide what they need a thermometer for, i.e., measuring body temperature, checking food, monitoring home temperature, or using specialized equipment in the lab and industrial settings. Note that each type comes with different advantages, costs, and temperature ranges. Deciding between analog and digital models is also crucial, with digital and non-contact models increasing in popularity.

When it comes to thermometers for medical use, which are among the most popular items for sale, users should consider safety features and ease of use, especially if the unit will be used on children. Note that good meters are often FDA approved and recommended by pediatricians and other professionals, with forehead measurements being one of the most effortless ways to check if a child is feverish.

Specifications: Accuracy is one of the most important features to consider. Fast readings and regular updates, as well as stable consecutive measurements, are essential for a unit to be considered reliable. Note that thermometers should not be affected by the surrounding temperature. Readability is another important feature to look for: ideally, readings should be in both the Celsius and Fahrenheit scales, while displays (LED or LCD) should be easy to read. Note that some medical thermometers used on children have a backlit display, so no additional illumination is needed at night, whereas some home temperature meters have night mode options to improve user comfort and sleep.

Design features should be handy, with push-button simplicity and curvy edges for safety reasons. For home meters, in particular, mounting options and aesthetics are important. When it comes to instant thermometers to check food, users should look for probes from stainless steel or other high-quality material to avoid contamination.

Total costs: Deciding on a budget is fundamental. Note that infrared thermometers can be more costly than other units, with tympanic infrared thermometers (used to measure the temperature inside the ears), forehead infrared thermometers (for body temperature readings), and non-contact infrared thermometers (for surface temperatures) being in-demand infrared meters.

Additional features, such as audible beeps and temperature alarms, as well as memory recall and automatic shut-off options, are highly beneficial. When it comes to home temperature meters, additional functionalities (for example, a humidity meter and a thermometer in one) can also be handy. Last but not least, accessories, such as protective cases and extra probes, can add to the final price of a unit.


Best Thermometers for Sale

We realize that choosing a thermometer can be a challenging task. Therefore, based on different applications, parameters, and user reviews, we present some of the best units for sale:

  1. Body temperature meters: Measuring body temperature is crucial, especially after an injury or an infection. As explained above, users can choose from the different ear, oral, rectal, underarm, and forehead thermometers. Units with fast measuring times, easy-to-read displays, and high accuracy (e.g., +/- 0.2 degree) are recommended.

1.1. iProvèn DMT-489 Digital Tympanic Thermometer with Forehead Function

It is a great ear thermometer with impressive forehead functions too. This unit reveals advanced performance based on innovative calibration technology; it reads the temperature in less than a few seconds. With its convenient design, loud beep and fever alarm, and recall functions (up to 20 readings), this dual-mode unit is suitable for both children and adults. Note that iProvèn DMT-489 is clinically tested and FDA approved.

1.2. Braun ThermoScan 5 Ear Thermometer – IRT6500

It is a powerful unit ideal for measuring ear temperature. The meter comes with 21 disposable lens filters to ensure safe and hygienic measurements. Thanks to its patented pre-warmed tip and ExacTemp technology, this model is not only accurate but comfortable to use. Note that readings are fast and can be displayed in both Fahrenheit and Celsius. With a variety of benefits, it is no surprise that this thermometer is favored by medical professionals across the globe.

1.3. PyleHealth Bluetooth Ear Digital Thermometer

It is an impressive digital Bluetooth model that supports ear and forehead measurements. The unit employs infrared technology to guarantee high accuracy. Additionally, the meter has built-in memory (for the last eight readings) and switching functions (between Fahrenheit and Celsius). One of its most important features is the Pyle Health Thermometer App that allows Bluetooth wireless data transfer and storage of up to 50 readings. Note that users can choose between three colors when purchasing, which makes this thermometer a great gift choice.

1.4. Simplife Forehead Thermometer with Ear Function

It is a popular meter with high accuracy and reliable calibration technology. The unit has advanced memory (up to 20 readings) and fever alarm functions (red display and 10 short beeps), as well as convenient design features to help users switch between Celsius and Fahrenheit with ease. Note that this versatile thermometer has been approved and calibrated for medical use.

1.5. Innovo Medical FR201 Non-Contact Forehead Thermometer with Silent Mode

It is a sophisticated non-contact thermometer for forehead use, ideal for babies, young children, and professional medical settings. The unit is based on proficient non-contact measurement technology, so cross-contamination is avoided. Users simply need to point the meter ½-2 inches away from the center of their child’s forehead to get accurate readings, even when the child is asleep. Note that this thermometer is clinically approved (with an accuracy of +/-0.4°F) and is also suitable for measuring the temperature of objects (e.g., baby bottles).

1.6. Braun PRT1000 High-Speed 3-in-1 Thermometer

It is a highly versatile thermometer. With its soft tip, Braun PRT1000 is suitable for underarm, oral, or rectal use. Moreover, this unit is equipped with a large display and advanced memory features to help users read and monitor temperature changes. Note that the meter beeps when readings are completed.

1.7. Kinsa Smartphone Thermometer

It is an innovative axillary, oral, and rectal meter, ideal for both adults and children. Note that the model has a 10-second reading time to ensure comfortable use. The unit is designed to connect to a smart device via a headphone jack, so an interactive app can present color-coded results and engaging data. Note that this thermometer is compatible with different smart devices, such as iPhone 4S, 5, 5c, 5s; Samsung Galaxy Note 2, Note 3, and Note 4; Samsung Galaxy S3, S4, and S5.

  1. Thermometers for home use: Checking the temperature indoors is essential for ensuring thermal comfort and health. Note that users can choose between analog and digital thermometers, including apps, to track temperature fluctuations. Some thermometers can show not only temperature but humidity and time/date, while others can simply become beautiful additions to your interior space. Galileo thermometers, in particular, are highly attractive units.

2.1. ThermoPro TP55 Digital Hygrometer Indoor Thermometer

It is one of the most precise thermometers on the market. Note that this product can measure both humidity and temperature in both Fahrenheit and Celsius. The unit is equipped with professional-grade sensors and has high accuracy (2-3% RH and +/-1°F/°C), with readings that update every ten seconds. With its large touchscreen display, this unit is an attractive and powerful meter at the same time.

2.2. BENGOO Home Humidity Monitor and Indoor Thermometer

It is a multifunctional digital humidity monitor and thermometer. Its large LCD display with clear icons can display humidity levels (dry/comfort/wet), as well as air conditions (high/ideal/low) and temperatures (in both Fahrenheit and Celsius). Note that such measurements are essential to improve the thermal and environmental comfort indoors, especially for infants and people with respiratory and skin diseases. Additionally, there is a record mode and current trends functionality. We should note that this monitor has two mounting options: tabletop and wall-mountable design.

2.3 AcuRite 00795A2 Galileo Thermometer with Glass Globe Barometer

It is a beautiful temperature meter inspired by Galileo’s thermometric invention. Note that the unit is filled with colorful spheres and is based on the basic principles of buoyancy and air pressure. Besides, this attractive set comes with a glass globe barometer – all mounted on an elegant wood base.

  1. Instant meters: Instant meters are mainly used for measuring food temperature and safety. We should note that products that have reached the so-called danger zone (40°F-140°F) and stayed in it for more than two hours are no longer safe to eat.

3.1. ThermoPro TP03 Digital Instant Read Meat Thermometer

It is an instant reading meter with a temperature range of around -58°F to 572°F (-50°C to 300°C), and an accuracy level of +/-0.9°F. With its foldable probe design and magnetic back, the unit is highly convenient and portable, ideal for cooking, grilling, and barbequing. Note that this thermometer is powered by AAA battery (included).

3.2. GDEALER Instant Read Thermometer – Super Fast Digital Food Thermometer

It is a great instant thermometer with a convenient digital readout and a stainless foldable tapered probe (4.3 inches or 11 centimeters). The unit takes accurate readings (+/-0.1℉, between -4℉ to 392℉) in no time (4-6 seconds for meat and 4-20 seconds for liquid). Note that its range is of -58℉ to 572℉ (-50 to 300℃), which makes it ideal for checking the temperature of meat, coffee, candy, and bathwater.

3.3. Alpha Grillers Instant Read Meat Thermometer for Grill and Cooking

It is an easy-to-use thermometer with accurate and fast readings (2-3 seconds). Note that this IP67 rated waterproof unit has a range of -58℉ to 572℉, with an accuracy rate of +/-1 degree. Besides, the set includes batteries, instructions, a meat temperature chart, and four Velcro dots – all wrapped in a beautiful package.

  1. Noncontact meters: Non-contact thermometers are advanced units that rely on infrared technology. Such meters can help users measure the surface temperature of objects in various areas, such as car maintenance, cooking, engineering, and other industrial settings.

4.1. Etekcity Lasergrip 630 Dual Laser Digital Infrared Thermometer

It is a great infrared unit with high accuracy (+/-2%; +/-2°C) and adjustable emissivity (0.1-1.0) for different surface textures. Additionally, the dual laser pointers the unit comes with can ensure high precision and low response time (of less than 500 Ms). Note that the unit has a measuring range of -58°F to 1076°F (-50°C to 580°C) and distance to spot ratio of 16:1. This Class 2 laser (0.3-0.49 mW) is FDA, FCC, and CE compliant, suitable for different applications, such as HVAC, real estate, and engineering settings.

4.2. Etekcity Lasergrip 1080 Non-Contact Digital Laser Infrared Thermometer Начало на формуляра

It is another powerful infrared unit with surface temperature ranges from -58℉ to 1022℉ (-50℃ to 550℃) and low response times (under 500 Ms). Note that to achieve higher accuracy, the distance between the meter and the measured object should be around 14.17 inches (36cm). With its convenient design, backlit LCD screen, low battery indicator, and auto-off functions, this unit is ideal for home repairs, cooking, and other do-it-yourself activities.


Maintenance and Safety Tips

In order to provide accurate and reliable readings, thermometers have to be handled, stored, and cleaned properly.

  • When it comes to measuring body temperature, especially on children, people should be careful not to harm the ear canal or the rectum of their child. Note that rectal and ear readings tend to be higher than oral and armpit measurements. Cleaning and sterilization are essential to eliminate cross-contamination. To avoid infections, disposable units are often preferred in hospitals and other clinical settings. Working with mercury-style units, on the other hand, requires special considerations, especially around children and pets.
  • Thermometers for home use should not be placed in direct sunlight or too close to the ground (e.g., pavement) as the instrument can absorb heat from it. In contrast, placing a unit too far from the ground can make it prone to radiative cooling. While it’s true that thermometers should be protected from rain and other harsh weather conditions, good airflow is crucial to achieving accuracy.
  • Thermometers for food safety and instant measurements should be cleaned properly to eliminate the risk of food contamination. Stainless steel is recommended for probe meters in order to avoid rust and toxic compounds. Furthermore, users should follow general safety precautions when working with kitchen equipment to prevent burns and injuries.
  • Last but not least, users should be extremely careful when utilizing thermometers in laboratories, meteorological technologies, automotive maintenance, aircraft engineering, and other industrial settings to avoid direct contact with extreme temperatures and prevent accidents.


Some Interesting Facts about Temperature

Even though the term temperate is often mentioned in science and everyday settings, here are some interesting facts about temperature measures:

  • Temperature measurements express how cold or hot something is and can affect the physical properties (e.g., density, electrical conductivity) of all materials (solid, liquid, gaseous, or plasma).
  • The temperature of a substance depends on the speed of its molecules; the faster the molecules, the warmer the substance.
  • The Planck temperature is the hottest temperature believed to have occurred after the Big Bang, which stands at 10^32 Kelvin.
  • Temperatures in the universe range from 3,500,000,000 Kelvin to 3 Kelvin.
  • The center of the Sun reaches 27 million degrees Fahrenheit, while its exterior temperature is around 10,000 degrees Fahrenheit – approximately the same as the center of the Earth.
  • The coldest temperature on Earth was recorded at Vostok Station, Antarctica, in 1983 at -128.6°F (-89.2°C).
  • The hottest human-made temperature reached 7.2 trillion degrees Fahrenheit, which was recorded in the Relativistic Heavy Ion Collider at the Brookhaven National Laboratory.
  • Extreme weather and climate change keep challenging societies and ecosystems.


Thermometers: Conclusion

Thanks to the advancements in thermometric technology over the centuries, today’s users can choose from different models (e.g., non-contact units) based on different technology (e.g., infrared techniques). That said, prospective buyers should consider three major factors: requirements, specifications, and total costs, with accuracy, safety, and readability being essential parameters to compare.

Given the fact that temperature measurements are essential, it’s no surprise that modern thermometers are invaluable and in-demand meters in science, medicine, food preparation, and industrial settings.

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