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Digital Thermometer vs Mercury Thermometer: Which is better?

mercury thermometer vs. digital thermometer

Thermometers have various uses from gauging food temperatures to gauging body temperatures and more. But when it comes to selecting a thermometer, which is best, a digital thermometer or a mercury thermometer? Well, as it turns out, the type of thermometer you choose does indeed have a significant impact on your temperature reading as well as your all-around safety, so let’s take a look at the following digital thermometer and mercury thermometer comparison to check out a few reasons why.

Digital Thermometer vs. Mercury Thermometer

Mercury thermometers have been around for quite some time; however, as of recent, digital thermometers have begun to take over, which is cause for us to research their benefits over mercury thermometers. In fact, digital thermometers have several advantages over traditional mercury thermometers, which the following comparisons will reveal.

Why is a Digital Thermometer Better Than a Mercury Thermometer?

1.  Digital thermometers provide faster results

Digital thermometers provide fast results as opposed to mercury thermometers whose readings are slower to realize because you have to wait for the mercury to heat and then slowly rise to display the temperature. However, digital thermometers are designed using advanced technology that enables them to provide instant results on the spot, which means no more waiting for crawling hot liquids to rise.

mercury thermometer theory

Mercury thermometers are designed utilizing the idea that mercury expands with heat.

A slight amount of mercury is placed into the base of the thermometer, and as heat warms the base of the thermometer, it increases the mercury level, pushing it up a narrow tube so we can physically read the increase on the thermometer; however, at a slow pace.

Mercury is used because it remains liquid throughout various temperatures as opposed to water, which freezes in colder temperatures. Mercury thermometers are also designed to withstand boiling temperatures.

2. Digital thermometers provide better accuracy

Besides the fact that digital thermometers provide faster readings, they are also slowly replacing conventional mercury thermometers because they include various technologies that provide better accuracy, which has even made them a popular choice for various professional industries. In fact, some digital thermometers also include thermocouple sensors on the probe that have been measured and calculated to provide very high accuracy and without the need for calibration like mercury thermostats.

Calibration refers to the measurement that is performed on a thermometer to check the readings. Once the thermometer is tested, it is then adjusted or re-calibrated so that it provides the proper reading. To do so, the thermometer is placed in a boiling hot or ice cold bath for adjustment using the temperatures.

3. Digital thermometers are safer to use

Another reason digital thermometers, such as the ThermoPro Digital Thermometer, are becoming a more popular choice over mercury thermometers is because they are also safer to use.

Mercury thermometers are most often made of glass, which is inserted into food to gauge the temperature. However, glass is very fragile, which means, it can easily become broken. Mercury is a toxic chemical, which if released could contaminate the body as well as surrounding areas, rendering it unsafe. It is also difficult to clean up. In fact, mercury thermometers are being phased out by a number of countries across the globe and not allowed to be sold to customers due to the hazard they pose.

Pouring liquid mercury

On the other hand, digital thermometers utilize metal components, which are much sturdier and contain no harmful chemicals for improved safety. There are also some models that can be used to measure temperatures far above the boiling point of mercury, and they can also be used to measure temperatures far below mercury’s freezing point.

How do Digital Thermometers Show Temperature Without Mercury?

As stated earlier, digital thermometers utilize metal components along with advanced technology to provide instant results. Metal has a natural resistance to heat. As metal gets hotter, it expands at an expected rate, which is used to determine the temperature.

Some digital thermometers also use tiny electronic circuits that help gauge the temperature. Various temperatures allow for different flows of energy. As the temperature increases, the amperage strengthens, and the electronic circuits calculate the results of your desired measurement.

In the case of thermometers that utilize a thermocouple probe, the thermocouple is created by attaching two opposite metals, which generates a slight voltage, based on the temperature. The voltage of these various metals has been tested and arranged to provide extreme accuracy.

There are also thermometers that utilize microelectronic mechanical systems (MEMS), which operates similarly to a bimetallic strip. In fact, it uses a bimetallic-like strip that is embedded on the MEMS crystal with its end being held by a capacitor plate. As the temperature increases, the strip responds by diverting this increase, which in turn alters the changes between the plates, thereby adjusting the system’s electronic charge capacity. The system’s electronic charge capacity can be calculated by the circuit, which in turn is used to gauge the temperature.

What is the Principle of Digital Thermometers?

resistance thermometerWhile the idea of a mercury thermometer is based on the theory of the expansion of mercury when it is heated, a digital thermometer solely utilizes a circuit; which means it relies on the effectiveness of the microchip. In fact, the principle of digital thermometers is mostly based on metal’s resistance to heat. The resistance increases in relation to the temperature. An electromotive force streams through an electrode that calculates the current and the microchip in the thermometer translates that measurement into a digital reading.

Does a Digital Thermometer use Alcohol or Water?

A digital thermometer relies on neither alcohol or water for its readings as water can freeze at certain temperatures, and alcohol decreases the accuracy because it is more vaporous than mercury, so it will evaporate. As the temperature drop, some of the alcohol can also remain behind, which can also cause an inaccurate reading. Instead, digital thermometers contain metal parts that react based on voltage to provide faster and more accurate results than alcohol or water.


In the end, which type of thermometer you select makes all the difference between receiving a slow, unpredictable temperature reading and receiving fast, most accurate results. You should also consider the overall safety of the thermometer when making a choice.

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