According to both CDC and WHO, temperature measurement is one of the crucial aspects of COVID-19 prevention. Companies must organize the process of temperature measurement and log all of the results. We conducted an experiment to see what type of temperature measurement is the best for businesses ― from a liquid thermometer to the autonomous screening terminal.
Our main criteria for this experiment is measurement accuracy. This is the most important aspect of the whole process as it determines the safety of visitors and employees at each building.
10 people overall were involved in the experiment ― they are employees at different companies in a coworking building, including developers, sales, marketing and project managers. 7 men and 3 women were our participants, their average age is 27 years old.
Each visitor measured temperature with these 4 devices:
- Thermal imager
- Liquid galinstan thermometer
- Contactless thermometer ― pyrometer
- Promobot Thermocontrol station
The results received from the liquid thermometer are our standard for this experiment. The one device that is the closest to a liquid thermometer will be determined as the most accurate.
Why were the liquid thermometer results decided as the standard? In liquid thermometers, a liquid metal is expanding in a sealed glass tube. Sometimes liquid galistan thermometers are also called maximum thermometers ― an alloy of gallium, indium and tin reaches its maximum temperature without any external factors affecting it. However, it’s not possible to use liquid thermometers to measure multiple people ― each body temperature measurement takes around 10 minutes with them.
We collected all of the results in the table below. Each row signifies a single person’s results. The difference from liquid thermometer results can be found in parenthesis; green means it is the closest to our standard, red means it differs the most from it.
The most significant difference could be found in thermal imager results. The average difference was -0,5 degrees with maximum being -0,7 degrees, which is a critical error. What is even more important is that most of the time imagers lower temperature automatically: so for example a person with 37,1 body temperature can be measured at 36,6, which can result in allowing a sick person enter the building.
The second least accurate device is a pyrometer. On average it lowered the results by 0,1 degrees, upwards to 0,4 degrees. Of all 10 measurements only 2 coincided with liquid thermometer results ― just 20% of the overall number of tests.
The best results were demonstrated by a contactless screening device Thermocontrol: its average result was the closest to all 10 results from the thermometer ― 36,5 degrees. In just 3 out of 10 measurements a deviation of 0,2 degrees was detected, and just once it lost against a pyrometer with a result of 36,6 degrees against 36,5.
Aside from measurement accuracy we also considered if an additional operator is required to conduct the measurement. The importance of that is significant: first of all, there are numerous errors that can be attributed to the human factor. Due to those errors the results can be different ― if a person points a pyrometer to the wrong part of the person’s face, the results will be drastically different. Second of all, any additional personnel requires additional expenses. Finally, there is always a chance that the operator can become a carrier of the disease: the virus can affect that person or transmit from them to other people. You can’t, however, catch a virus through a contactless terminal.