How to Use Different Kinds of Thermometer

Thermometers are something that you are most likely to find in every household because they are indeed a most important instrument to own as it gives you a brief overview of a person’s health.

It is advised that the temperatures are recorded even when a person is healthy; this is especially apt for young children. It gives you a brief insight into their health, and regular measuring may let you know if there is something wrong.

There are various kinds of thermometers and method to measure the temperature in different aged people. It is necessary to follow the prescribed protocol; otherwise, you may get erroneous results. In this article, we will guide you to do it in the right way.

Different Types of Thermometer

Here we listed some of the famous thermometers used these days.

  • Probe Thermometer
  • Digital Thermometer

These thermometers have been on the scene for quite a while now. The system of using the two are alike. The only difference between a probe and a digital thermometer is their design.

Probe Thermometer

what is probe thermometer

A probe thermometer consists of a glass tube filled with Mercury or Ethanol, a measurement scale, and a probe at the end.

Mercury is a highly toxic substance which if exposed to the room, may have harmful effects. Due to the toxicity levels of mercury, this traditional substance is being replaced by alcohol-based substances such as ethanol.

The measurement on the probe thermometer works on the principle of thermal expansion. When the mercury is subject to the body's heat, it expands due to the heat and rises. This process tells you about the temperature of the person. 

How to Use a Probe Thermometer


Step 1 - Wash your hands

Wash your hands with soap and then wash the thermometer. Lower the meter to the starting point by shaking it vigorously. Once the temperature is lowered, you are ready to take the readings.


Step 2 - Place the thermometer

Place the tipping probe under the person's tongue, whose temperature needs to be determined. Keep the probe under the tongue for 5-10 minutes. 


Step 3 - Check the readings

After the expiry of this period, remove the thermometer, and observe the readings. You can do this more than once to verify authenticity.

Probe thermometers are advised to be used on children above the age of 7 and adults as babies, and some children cannot hold the thermometer under their tongue for a long time.

Digital Thermometer

The digital thermometer has a different design altogether. There is no mercury or ethanol present, which determines the person's temperature in the probe thermometer. Instead, a digital screen is placed to show the temperature.

A digital thermometer possesses a computing unit and a resistor. The sensory unit of the thermometer tends to detect the change when it is applied.

The thermometer mechanism changes the difference in the resistance into a difference in temperature and renders a numerical value in degrees. This is the temperature. You can choose your preferred unit of measurement between Celsius and Fahrenheit. 

The digital thermometer classifications are given below, and the method of using them varies as well.

  • Oral Thermometer
  • Rectal Thermometer
  • Axillary Thermometer
  • Forehead Thermometer

How to Use a Oral Thermometer

what is digital thermometer

An oral digital thermometer must be placed under the person's tongue, just like in the case of a probe thermometer. After a few minutes, the readings will appear on the screen with the chosen unit of measurement.

This method is ideal for children above the age of 7 and all the adults who can hold the device under the tongue. Any disturbance to the position may lead to faulty readings.

How to Use a Rectal Thermometer

how to use a rectal thermometer

In a rectal thermometer, the device is inserted into the rectum of the person. You need to be very gentle while handling the rectal thermometer and hold the baby properly to get accurate readings.

This device is ideal for babies under the age of 3 who cannot be subject to an oral thermometer because of their inability to hold it. It is to be noted that the rectal thermometer should not be used for people above the age of 3.

How to Use a Axillary Thermometer

In the Axillary thermometer, the device is placed in the armpit of the person who cannot be subject to the oral method because of safety reasons.

This is mostly done in the case of young children and older people. This method can be deemed inaccurate compared to oral and rectal methods but has a quick and safe process.

How to Use a Forehead(temporal) Thermometer

how to use temporal thermometer

The forehead thermometer specializes in detecting fevers and comes with a warning system for the same. It has different designs and is more developed than any of the previously discussed thermometers. So, we published a separate how-to guide for the forehead(temporal) thermometer, please check it here.


Being aware of a person's temperature can be good because you can detect the underdeveloped fever and take the necessary course of action.

A person suffering from mild fever can be treated at home, and the further worsening of the health can be eradicated. If the person is suffering from a high fever, they should be consulted with the doctor immediately and should be given necessary medical attention.

All these steps can only be undertaken if the temperature is appropriately undertaken. So check our forehead thermometer buying guide and choose the best one for you.

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About the Author


I am Tim, a weather enthusiast who loves to watch hurricanes and all other harsh weather conditions. I studied B.Sc(Meteorology) at the University of Miami. With excellent knowledge of Weather Forecasting, Meteorology, and Environmental Science, I am currently working in San Francisco as a Meteorologist. Also, I am a member of The Weather Channel and AccuWeather. In this blog, I will write a detailed review of Weather instruments that you need for survival and other activities.