Having become quite well-known especially after the start of the epidemic from Covid-19, the new Chinese Coronavirus that also arrived in almost every country, guns to measure the temperature use a rather old technology that is widespread in different types of thermal scanners, professional and not. But how do these devices work? And are they reliable?
They are called in a thousand ways: thermo scanners, laser thermometers, remote thermometers, infrared thermometers. Many names, to indicate one of the most discussed tools of recent days, which have become one of the main weapons for temperature control, especially in airports, after the great spread of Covid-19, the new Chinese Corona virus unfortunately also arrived in Italy. But how do these particular thermometers work? And, regardless of the actual usefulness of checking the temperature to people just landing at the airport, how reliable are they?
How a gun works to measure the temperature:
Although there has only been a lot of talk about it recently, the technology of so-called “temperature guns” is by no means new. For years these particular devices have been used for measuring the temperature of surfaces, materials and people. And it is even possible to buy real smart thermometers, produced with this technology and which connect to the smartphone, or accessories to connect to your mobile device to transform it into a thermoscanner.
But whatever the intended use of this technology is, all laser thermometers, as well as guns to measure the temperature so much discussed in recent days, work by measuring a particular physical value, typical of any material: thermal radiation.
Thermal radiation (i.e., heat) is nothing more than electromagnetic radiation that is emitted from an object and that is caused by its temperature. During the thermal dispersion of an object (or a person) it is possible to measure the energy carried by the electromagnetic waves and, therefore, to measure its temperature without the need to touch the body involved in the measurement.
The point is that every object emits electromagnetic radiation whose intensity depends on the emissivity of the material, for this reason the guns to measure the temperature (as well as all the other thermo scanners) to be able to precisely calculate the temperature of the object towards which they are pointed, they also measure the reflected radiation and the transmitted radiation: the sum of these three characteristics forms 100% of the electromagnetic radiation exiting the body.
Are they reliable tools?
The reality of the facts is that any type of measuring instrument (especially the more complex ones) carries with it a margin of error which, in the case of guns for measuring the temperature, may also depend on external factors. The first and most important mistake that could happen in the remote measurement of the temperature of a body, is that concerning the emissivity of the object: if not set correctly, this value can lead to rather important reading errors, but it is a factor that in guns to measure the temperature could be considered not influential, precisely because these particular laser thermometers are produced and calibrated to measure the temperature of the human body.
But think of the dust, dirt or other electromagnetic radiation commonly present everywhere. These are the factors that could make the remote reading of the temperature of the temperature less precise and reliable, disturbing variables that are positioned between the body to be analyzed and the thermometer. Furthermore, since the radiation is invisible to the human eye, it is possible that the body being measured is reflecting or transmitting radiation from external sources such as cooling systems, lights, or any other source that emits heat or cold.
All factors that have given way to a long and interesting debate about the real accuracy of guns for measuring temperature, defined as not necessarily accurate even by James Lawler, of the Global Center for Health Security of the University of Nebraska, who doubts the effectiveness in an interview with the New York Times: “Some of these temperature detectors are only for appearance,” said Dr. Lawler, arguing that these devices often tend to register temperatures lower than reality.