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How does a medical thermometer work?

Views: 4     Author: Site Editor     Publish Time: 2021-04-30      Origin: Site

Fever is an external manifestation of the body's defense against pathogens. However, fever cannot be directly judged, but needs to be measured with a medical thermometer. A medical thermometer is an instrument that everyone needs in their homes. I believe you have at least used one of the four thermometers: mercury thermometers, infrared thermometers, electronic thermometers and "pill-type" oral thermometers. Do you know the working principles of these medical temperatures? I will expand on the principles for you next.


Here is the list of the article:

l What is the working principle of a mercury thermometer?

l What is the working principle of an infrared thermometer?

l What is the working principle of an electronic thermometer?

l What is the working principle of an oral thermometer?


What is the working principle of a mercury thermometer?

The working substance of the mercury thermometer is mercury. The neck of the lower part of the mercury thermometer near the liquid bubble is a very narrow curved neck. When measuring the body temperature, the mercury in the liquid bubble expands by heating, and the mercury can rise from the neck to a certain position in the tube. When it reaches thermal equilibrium with body temperature, the mercury column is constant. When the thermometer leaves the human body, the outside temperature is low, and the mercury shrinks in volume when cold, and it is disconnected at the curved neck, so that the part of the mercury that has risen into the tube cannot return. The height of the mercury column reached when it comes into contact with the human body is still maintained.


What is the working principle of an infrared thermometer?

In nature, all objects whose temperature is higher than absolute zero are constantly emitting infrared radiation energy to the surrounding space. The size of the infrared radiation energy of an object and its distribution according to wavelength has a very close relationship with its surface temperature. Therefore, by measuring the infrared energy radiated by the object itself, its surface temperature can be accurately determined, which is the objective basis on which infrared radiation temperature measurement is based.

The infrared heat radiation of the human body is focused on the detector, and the detector converts the radiation power into an electrical signal, which can be displayed in Celsius (or Fahrenheit) after being compensated for the ambient temperature.


What is the working principle of an electronic thermometer?

The electronic clinical thermometer uses a temperature sensor to output electrical signals. The electronic clinical thermometer directly outputs a digital signal or converts the current signal (analog signal) into a digital signal that can be recognized by the internal integrated circuit, and then displays the temperature in digital form on the display. It can record and read the highest value of the measured temperature.

The core component of an electronic thermometer is the NTC temperature sensor that senses temperature. The resolution of the sensor can reach ±0.01℃, the accuracy can reach ±0.02℃, the response speed is less than 2.8 seconds, and the annual resistance drift rate is ≤0.1% (equivalent to less than 0.025℃).   


What is the working principle of an oral thermometer?

The slice thermometer is only the size of a business card, with a length of 6-7 cm and a width of about 0.5 cm. It is covered with neatly arranged dots with numbers. After the body temperature test, the dots below a certain value will all darken, while the color of the other dots remains unchanged. The user can determine the body temperature based on the above changes.

Our company supplies mercury thermometer, electronic and digital thermometer. If you want to buy a medical thermometer for emergencies, welcome to contact us, We will serve you wholeheartedly. You can contact our company, LANYI MEDICAL DEVICE CO.LED.

You can contact Mr.Feng, his phone number is 86-17725675881. Or you can email us, Our website is or


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