A Mini Guide of Thermometer

The thermometer is a handy and well-recognised device that finds its use every now and then. Everyone is aware of it and its applications. But then, do you know its functioning? Are you sure about its types and accuracy of readings? Do you want a detailed outline of thermometers? You have reached your destination.

Prior to that, let’s get to know each other.

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A Brief Intro and History

A thermometer is, technically, a device that measures the temperature. In simple terms, it measures the degree of hotness or coldness, which is otherwise called the temperature gradient. The output obtained is usually in degree Celcius, but Fahrenheit and Kelvin’s measures are also available.

The birth of the principle of thermometer is around 2000 years ago. Thermoscope was the first version and, it just detects the temperature change. One can’t read the measure of change in it since it didn’t have a scale. The setup was like a tube in which water falls and rises according to the temperature. Air expands and contracts in the bulb attached to the tube top when temperature increases and decreases, respectively. Later on, advancements in technology helped convert the thermoscope into a thermometer. 1714 marks the year when the first reliable thermometer came into existence.

Essential Parameters

There are quite a few parameters to check in a thermometer. You need to know them since you will encounter them while buying or using one of such devices. These essential factors are:


As the name suggests, it refers to holding the observed temperature value. Early thermometers didn’t have this ability. The reading will change as soon the surrounding environment changes. But nowadays, most of them comprise registering capacity, which enables the device to hold a recording indefinitely. Registering can either be mechanical or electronic. In the former, the reading is reset manually like, shaking or taking another measurement. In the latter, the measure is either in computer or in the device memory. One need not check it since it will be available but should be aware of it.


It is the process of correcting errors. One can execute calibration by comparing it with another thermometer. You can also check it with the help of a known temperature point. This process is necessary for those who use conventional thermometers. The “International Temperature Scale of 1990” removes such a process. Thus, most of the modern devices calibrate by themselves.


This factor determines how on the point the measurement is. It implies, even the smallest of change is observable. This parameter is also called resolution. 0.1 degree Celcius is the range for clinical thermometers. Although it is often confused with accuracy, they are not the same. The more precise the device is, the better it is. It is a significant factor to consider since it provides the exact reading.


It is that parameter, which determines how correct the output is. You can check it by seeing how close the measure is to the known fixed point. In simpler terms, one can ensure that the device is showing the utmost correct value or not with the help of this factor.


It is the parameter that enables us to check the thermometer. If the same equipment produces the same result for the same measure, then it is reproducible. It is necessary to see if the equipment works consistently. Proper working and consistency make a reliable device.

Types of Thermometer

The working and parts of the thermometer changes vary along with the types. The types vary according to the purpose, such as nanothermometry, cryometer, food safety, environment, etc. The standard types of medical purpose thermometers are as follow:

Digital Thermometer:

This type of equipment depends on a heat sensor for obtaining temperature. Digital ones are more accurate when compared to conventional ones. They are easy to use and handle for any patient. The recent versions do not even need contact with the patient to show the reading. The display provides the output in a very short period. They are further subdivided based on the placing position.

Note- These types are also available in traditional types but, digital is any time preferable.

Oral Thermometer:

The thermometers that are placed in the mouth for measurement purposes fall under this category. The usual reading is around 37 degrees Celcius. It is apt for children above 3 years and also for adults. The values are pretty much accurate.

Tympanic Thermometer:

They are placed in the ear canal and, the reading is obtained with the help of IR ray technology. Their measurements are always a unit degree higher in comparison to oral. The output here is also quick and accurate. It is any time better than oral and temporal when considering children.

Temporal Thermometer:

It is also known as the forehead and non-contact IR thermometers. The temperature of the superficial temporal artery is taken through infrared sensors. This value is the one that the display shows. The highlight of this device is that doesn’t require any contact with the patient body. Though the value is 1 unit degree lesser than oral values, it is compatible and accurate for patients in any age group.

Mercury Thermometer:

One can infer from the name that this type is the liquid-in-glass thermometer. It was the only type of thermometer that was available. But, later it got replaced since it was not a very healthy option. They also have sub-categories like oral, rectal, etc. The common placement of this equipment was always the armpit.
Other advancements such as app-based, pacifier, laboratory, etc. thermometers are also available in the market. Thermocouple, bimetallic strip and other such types are specific for their field of use.




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