Types of Thermometer and its Uses

There are many types of thermometers available in today’s market, and it’s important to choose the right one for your specific needs. Before purchasing, it’s essential to understand the variety of thermometers available and how each type is suited for different applications. A basic office thermometer is not suitable for precise industrial measurements. In this blog, we emphasize the importance of selecting the right Infrared thermometer for your intended use. Let’s explore the different thermometers we offer and their ideal applications.

 

What is Thermometer?

 Thermometer is a tool used to measure temperature, whether it’s the heat of a solid like food, a liquid like water, or a gas like air. The most used temperature scales are Celsius, Fahrenheit, and Kelvin, each suited for different purposes.

Temperature Scales:

•  Celsius (°C): Widely used around the world, Celsius is the metric system’s temperature scale. It’s also the standard for most scientific measurements. On this scale, water freezes at 0°C and boils at 100°C, making it intuitive for everyday and scientific use.

•  Fahrenheit (°F): Primarily used in the United States, Burma, and Liberia, the Fahrenheit scale measures water freezing at 32°F and boiling at 212°F. While less common globally, it remains the standard for everyday temperature readings in these countries.

•  Kelvin (K): The Kelvin scale is vital for scientific research, especially in physics. Unlike Celsius and Fahrenheit, Kelvin begins at absolute zero, the point where no thermal energy remains. This makes it ideal for measuring extremely low temperatures, such as those found in outer space. Water freezes at 273K and boils at 373K on this scale.

Thermometric Fluids:

Thermometers often rely on thermometric fluids, substances that change in volume or pressure with temperature, to measure heat. Mercury and alcohol are two common thermometric fluids. Mercury is used in traditional thermometers because it expands uniformly with temperature, providing accurate readings. Alcohol, often coloured for visibility, is used in situations where mercury’s toxicity is a concern.

Each temperature scale and thermometric fluid serves a unique purpose, making it crucial to select the right combination for your specific needs, whether for everyday use, scientific research, or industrial applications. 

Different Types of Thermometer:

Thermometers come in a variety of shapes and sizes to meet different user needs. Primarily, they are used to measure the temperature of both living and non-living objects. For body temperature readings, a specific types of thermometer is typically used. In contrast, a different set of thermometers is employed in studies or laboratory testing to determine boiling and freezing points.

Thermometers can be categorized based on their functions into two main types:

1. Clinical Thermometers

2. Laboratory Thermometers

Clinical Thermometers:

Clinical thermometers, designed for measuring body temperature, have traditionally used mercury in a glass tube. Modern versions are digital and avoid the risks of mercury. Always sanitize thermometers before use. The average body temperature is 37°C, with a range of 35°C to 42°C. Digital thermometers are calibrated to this range for accurate readings.

Different types of clinical thermometers that we use to assess body temperature on a daily basis are as follows:

Digital Thermometer:

Digital thermometers use heat sensors and an electronic circuit to measure body temperature, displaying results on a screen. They can take readings from the rectum, under the tongue, or under the armpit. Compared to traditional thermometers, digital models offer advanced accuracy and ease of use. They are reliable, affordable, and widely available.

 

Electronic Ear Thermometers:

Electronic ear thermometers, or tympanic thermometers, use infrared technology to measure body temperature from the ear canal. They are particularly useful for children due to their quick measurement capability. However, they can be expensive and may give inaccurate readings if not positioned correctly or if there is excessive ear wax. They detect body temperature by capturing infrared energy emitted from the tympanic membrane, providing fast and convenient readings.

Forehead Thermometers

Forehead thermometers use infrared technology to measure temperature from the superficial temporal artery, a branch of the carotid artery. They are commonly found in public places like airports and malls due to their non-contact nature, which allows for quick and hygienic readings. However, they are generally less accurate than digital thermometers, with readings often being about 1°F (0.6°C) lower.

Pacifier Thermometers:

Pacifier thermometers are designed for babies at least three months old and offer a convenient way to measure temperature if the baby is comfortable with a pacifier. While easy to use, these thermometers provide only approximate readings and can be inaccurate if the baby isn't calm for a few minutes.

Plastic Strip Thermometers:

Plastic strip thermometers are used to get a general indication of whether a person has a fever, rather than precise temperature readings. To use one, place the strip on the forehead, and the color changes will suggest the body temperature. If the color indicates a high reading, it may signal a fever. However, these thermometers are not very accurate and are considered unreliable for precise measurements. They are disposable, single-use devices.

Mercury Thermometers:

Mercury thermometers, once the standard for measuring body temperature, are known for their accuracy. They consist of a glass tube with a mercury-filled bulb at one end. When placed under the tongue, the mercury column rises to indicate the body's temperature. Although highly precise, mercury thermometers are no longer commonly used due to safety concerns related to mercury poisoning and have been banned in many countries. They do not require batteries or electronic components, relying solely on the physical expansion of mercury to provide readings.

Laboratory Thermometers

Laboratory thermometers, also known as lab thermometers, are designed for measuring temperatures beyond those of the human body. They are used in labs to monitor boiling points, freezing points, and other specific temperature readings. Unlike clinical thermometers, laboratory thermometers are not suitable for medical or clinical use.

These thermometers typically have a temperature range from -10°C to 110°C and come in various sizes and shapes to suit different measurement needs. Additionally, maximum-minimum thermometers are used by weather forecasters to track the highest and lowest temperatures at a location.

Liquid-in-Glass Thermometers:

Liquid-in-glass thermometers consist of a sealed glass tube containing a liquid such as mercury or red alcohol. The liquid's volume changes with temperature: it expands as the temperature rises and contracts as it falls. The liquid level in the glass tube indicates the temperature. These thermometers are delicate due to their glass construction, so they are often housed in protective casings with temperature markings. They are convenient and cost-effective, requiring no power supply, making them suitable for use in areas without electrical access.

 

Bimetallic Strip Thermometers:

Bimetallic strip thermometers consist of two different metals bonded together. As the temperature increases, the metals expand at different rates, causing the strip to bend towards the metal with the lower expansion coefficient. This bending moves a pointer across a calibrated scale to indicate the temperature. Bimetallic strip thermometers are durable, affordable, and easy to install and use.

Thermocouple Thermometers:

Thermocouple thermometers, also known as thermal junction thermoelectric thermometers, measure temperature using two different metals joined together at one end. As the temperature changes, the metals produce a voltage due to the thermoelectric effect, which is used to determine the temperature. These thermometers are capable of measuring very high temperatures, up to 2800 K. They are known for their durability and wide temperature range, making them suitable for various industrial and scientific applications.

 

Pyrometer Thermometers:

Pyrometer thermometers, or pyrometers, are remote-sensing devices used to measure temperature from a distance. They determine temperature based on the thermal radiation emitted by an object, eliminating the need for direct contact. This makes pyrometers ideal for measuring the temperatures of moving objects or surfaces that are too hot or complex to touch. They are effective for temperatures exceeding 2000°C.

Platinum Resistance Thermometers:

Platinum resistance thermometers use a platinum wire to measure temperature. The electrical resistance of the platinum changes with temperature, allowing for precise temperature readings. While they offer high accuracy, they are somewhat slow in response. These thermometers are commonly used for measuring temperatures between 500°C and 2300°C.

Probe Thermometers:

Probe thermometers are widely used for measuring the temperature of food and liquids in real time. Their quick readings make them ideal for hygiene testing in retail and laboratory settings within the food industry. These thermometers typically feature a pointed tip for easy penetration and immersion. There are two main types of probe thermometers: fixed probes and wired probes.

Types of medical thermometers and their functions, applications, and uses, tailored to what you might find on the Medikabazaar website:

Digital Thermometers: These thermometers provide accurate and quick temperature readings and can be used orally, rectally, or under the arm. They are ideal for both home and clinical use, delivering results in about a minute.

Ear (Tympanic) Thermometers: Utilizing infrared technology, these thermometers measure temperature from the ear canal, offering fast and precise readings, especially useful for children and quick assessments.

Forehead (Temporal) Thermometers: Non-contact infrared thermometers that measure temperature from the forehead. They provide swift readings without physical contact, making them convenient for all age groups.

App-Based Thermometers: These digital thermometers connect to smartphone apps via Bluetooth, allowing for easy temperature tracking and health monitoring over time.

Pacifier Thermometers: Designed for infants, these thermometers measure temperature while the baby uses a pacifier, providing a simple and non-intrusive way to check temperature.

Mercury (Liquid-in-Glass) Thermometers: Traditional glass thermometers filled with mercury for precise temperature measurement. Although accurate, they are less common today due to safety concerns and are used less frequently.