Types Of Thermometers: How To Use & Accuracy Levels

Getting an accurate temperature reading helps doctors determine what's going on with your health and monitor your progress. Fortunately, there are tons of different medical thermometers to choose from, depending on what we need. The old-school mercury-filled glass ones have been used for a long time, but newer digital thermometers are becoming more popular because of their precision and user-friendly models. Let’s read more about thermometers and their types. 

When Was The First Thermometer Used? 

Thermometers have a 400-year-old history, starting with Galileo's invention of the thermoscope. Though different from modern thermometers, it laid the foundation for their development, leading to specialized instruments for measuring individual temperatures.

What Is A Thermometer? 

A thermometer is a unique tool for accurately measuring temperature. It helps doctors determine if someone has a fever or if body temperature falls below the normal range. The thermometer's sensor reacts to temperature changes like a bulb or probe. Heat detection by the sensor generates a signal, which gets converted into a numerical temperature reading.

Importance Of Thermometers In Measuring Temperature 

Thermometers play a vital role in measuring temperature, aiding doctors in diagnosing illnesses by accurately monitoring body temperature. Even slight temperature changes can indicate infections or inflammation. Healthcare professionals rely on thermometers to swiftly identify such conditions.

Also read: 12 Most Common Types of Fever In India: Know Their Symptoms & Treatment

Types Of Thermometers And How They Work

1. Contact Thermometers

Contact thermometers require physical contact with the body to measure temperature accurately. They use electronic heat sensors to record body temperature. These sensors can detect changes in heat and convert them into electrical signals, which are then shown as temperature readings on a screen.
Different types of contact thermometers exist, such as digital thermometer oral, axillary thermometer, and rectal thermometers. 

• Digital oral thermometers are commonly used by placing them under the tongue to measure temperature. 
• Axillary thermometers are placed in the armpit, ensuring good contact with the skin. 
• Rectal thermometers provide the most accurate readings for infants and young children as they are gently inserted into the rectum.

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How to use contact thermometers?

To measure temperature using a contact thermometer, follow these steps:

1. Wash your hands before handling the thermometer to maintain cleanliness.
2. Place the thermometer under the tongue and close the mouth for oral measurement.
3. Position the thermometer in the armpit, ensuring it has good contact with the skin for axillary measurement.
4. For rectal measurement, lubricate the tip of the thermometer, gently insert it into the rectum, and hold it until the reading is complete.
5. Please wait for the designated time, usually a few seconds to a minute, as specified by the thermometer, for it to provide a temperature reading.
6. Finally, read and record the temperature displayed on the digital screen for reference or further action.

2. Remote Thermometers

Remote thermometers, or non-contact thermometers, measure body temperature without touching the skin. Infrared (IR) thermometers are a common type of remote thermometer. These thermometers can capture the infrared radiation our bodies naturally give off and then convert it into temperature readings. Infrared radiation is a type of heat energy that we can't see with our eyes, but these special thermometers can detect it.

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How to use infrared thermometers?

To measure temperature remotely using an infrared thermometer, follow these steps:

1. Ensure the thermometer is set to the right mode, such as the forehead or ear mode. This depends on the model of the thermometer.
2. Point the thermometer at the forehead or ear of the person whose temperature you want to measure. It's important to maintain the recommended distance.
3. Press the button or trigger on the thermometer to activate the temperature measurement. This will initiate the process of capturing the infrared radiation emitted by the body.
4. The infrared sensor in the thermometer will detect the radiation and convert it into a temperature reading. This reading will then be displayed on the screen of the thermometer.

3. Temporal Artery Thermometers

Temporal artery thermometers are remote thermometers that measure temperature by scanning the temporal artery located on the forehead. These thermometers use infrared technology to detect the heat emitted by the artery and provide temperature readings.

How do they work? 

• These thermometers have an infrared sensor that captures the heat energy emitted by the temporal artery.
• The captured heat energy is converted into temperature readings by the infrared sensor.
• The thermometer's software analyzes the data collected by the sensor.
• The software processes the data to calculate the temperature.
• Finally, the temperature is displayed on the screen of the thermometer.

How to use temporal artery thermometers?

To use a temporal artery thermometer effectively, follow these steps:

• Ensure the thermometer is set to the temporal artery mode.
• Position the thermometer on the centre of the forehead, just above the eyebrow.
• Gently slide the thermometer across the forehead, following the hairline or the instructions provided by the manufacturer.
• The infrared sensor will capture the heat emitted by the temporal artery and display the temperature reading on the screen.

4. Tympanic Thermometers

Tympanic thermometers, or ear thermometers, measure temperature by detecting the infrared radiation emitted by the eardrum. They have a special probe that is gently inserted into the ear canal. The probe captures the thermal energy from the ear, which helps determine the temperature. These thermometers offer quick and comfortable temperature measurements and are suitable for both children and adults.

How do they work? 

Tympanic thermometers work by emitting an infrared ray into the ear canal. The ray measures the thermal radiation emitted by the eardrum, which is correlated with the body's core temperature. The thermometer converts the detected radiation into temperature readings and displays them on the screen.

How to use tympanic thermometers?

To measure temperature using a tympanic thermometer, follow these steps:

1. Gently pull the earlobe back to straighten the ear canal.
2. Insert the thermometer probe into the ear canal until it fits snugly.
3. Press the button or trigger to activate the temperature measurement.
4. Wait for the thermometer to provide a temperature reading, usually within a few seconds.
5. Read and record the temperature displayed on the screen.

5. Mercury Thermometers

Mercury thermometers were commonly used in the past and consisted of a glass tube filled with mercury. These thermometers relied on the expansion and contraction of mercury with temperature changes to provide readings.

Explore Mercury Thermometers

How do they work? 

• Mercury thermometers were based on the principle that mercury expands when heated and contracts when cooled. 
• As the temperature changed, the mercury inside the glass tube moved up or down, indicating the temperature on a scale. 
• However, mercury is a toxic substance; if the thermometer breaks, it could release harmful mercury vapour or liquid. Therefore, precautions are necessary during use and disposal to prevent mercury exposure.

How to use mercury thermometers?

• Place the thermometer tip under the tongue for oral measurement or in the armpit for axillary measurement.
• Hold the thermometer until the reading stabilizes, usually for a few minutes.
• Read the temperature by looking at the level of the mercury column in the glass tube.
• Dispose of mercury thermometers properly, following the guidelines for hazardous waste disposal in your area.

Which Is The Best Type Of Thermometer?

The best type of thermometer depends on factors like age, purpose of measurement, and personal preferences. For instance, 

• Contact thermometers (digital oral, or rectal) are accurate and suitable for all age groups.
• Remote thermometers (temporal artery and tympanic) are convenient for quick screenings.

Consult healthcare professionals or follow the manufacturer's guidelines to choose the suitable thermometer for your needs.

Summary

When it comes to measuring temperature accurately, various types of thermometers are available. From contact thermometers that require physical touch to remote thermometers that use advanced technology, each has its benefits. Whether it's the convenience of remote temperature measurements or the reliability of contact thermometers, these tools play a crucial role in healthcare. For more information, consult expert doctors.

Talk To Apollo’s Expert Doctors

Medically reviewed by Dr Sonia Bhatt.