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PROMAX thermal imaging solutions allow the access control by means of thermal images (thermography) and by the infrared temperature measurement.
Thermometers and thermal imaging in relation of COVID-19 Coronavirus – What is this about?
Health authorities around the world are proposing a number of measures focused on controlling the COVID-19 pandemic. These include access control to public places (airports, stations, factories, shops…) to try to prevent possibly infected people to infect other persons.
Since there is no way to find out who is infected or not, it is agreed that persons suffering of a fever must not access public areas and contact other individuals because given the circumstances there would be a good chance that fever may be caused by some process related to COVID-19.
The way to check if a person has a fever avoiding physical contact is using some kinds (please note the emphasis in “some kinds”) of infrared thermometers and thermal imaging cameras.
Fever or High Body Temperature - HBT?
There is no thermal camera nor infrared thermometer that allow finding out who suffers from Coronavirus. No matter the price. This must be pointed out to raise awareness and to avoid for scams. To be strict, they don’t allow identifying who suffers from fever either –as a medical concept. They just allow detecting temperatures higher than normal in the exposed areas or their bodies. This is known as High Body Temperature, from now on HBT for simplicity.
The HBT temperature controls have came to stay. Not only because of the COVID-19. There are many viruses and bacteria that can potentially push our healthcare systems to their limits as a result of the globalization, the overcrowding and generally speaking as a result of the modern way of life where there are high levels of social interaction.
How can I identify persons with HBT with no direct physical contact?
Well, I can use an infrared thermometer or a thermal image camera suitable for that application ensuring I use them the right way. The contactless measurement of a body’s surface temperature is performed by detecting its radiated heat.
THIS IS HOW THERMAL IMAGING CAMERAS WORK
Most of these devices are designed for industrial applications and feature a wide temperature range, usually from around -20 to +300 ºC with an accuracy of ±2 ºC in optimal conditions. This makes them very versatile and excellent products for an endless number of applications... but in a few words, when it comes to measure the temperature of a person’s face and a I get a value of 37 ºC I don’t know whether the real value is 35 or 39 ºC!!
The infrared thermometer for HBT
The infrared thermometers suitable for this application are known as forehead thermometers. They are calibrated just in the margin of interest (around 36 ºC) and they feature an accuracy of about 0.5 ºC when the temperature is measured at a distance of 10 cm. It is important to know beyond this distance (10-15 cm) they can NOT measure anything.
- Measurement margin: From 33 to 42 ºC
- Accuracy: 0.3 ºC
- Measurement distance: 10 cm
- Price: They are the most affordable option
- Use: Very easy to use
This kind of product is very easy to use for everyone with no need for previous training.
The thermal image camera for HBT
The thermal image cameras suitable for HBT are designed and calibrated to focus their measurement accuracy in the temperature range of interest (36 to 40 ºC). They are physically indistinguishable from the industrial cameras, therefore it is essential to carefully review the specifications to ensure whether they are suitable for HBT or not.
- Measurement margin: 20 to 50 ºC
- Accuracy: 0.5 ºC with frequent calibration
- Measurement distance: 2 meters
- Price: According to model
- Use: Requires evaluating the usage location. Requires training.
It is important setting properly the thermal camera for HBT monitoring?
The camera location is very important. For instance, focusing the camera to a sunny glass may dramatically affect the measurements. But there are not always options to choose from.
As a general rule the measurement distance is proportional to the measuring error. The further the camera is from the point to perform a temperature test, the greater the measurement error.
PERMANENT THERMAL CAMERAS FOR ACCESS CONTROL
At around 2 or 3 meters, it becomes important to evaluate other facets such as the thermal sensor resolution (notice we are NOT talking on the camera resolution). Usually they are separated specifications. For example 488x340 for the visual camera but 160x120 pixels for the thermal sensor. It is important to ensure at the distance the camera is installed it will be able to distinguish, for example, the face from the rest of the body.
This is a very easy to use product for anybody with no need for training.
What should I consider to choose the optimum camera location?
The technology behind this kind of thermal image cameras is called Uncooled FPA. As time passes, the environmental conditions around the camera vary: It gets colder or warm, the Sun rises or goes down, some lights are turned on or off... All of this affects the measurement! For HBT monitoring applications it is important to consider this, because the impact in the temperature measurements caused by these ambient temperature variations can be substantially important compared to the temperature values to measure.
In a typical application we will: Mount a camera on a tripod, configure it, take some reference temperatures and let it run. The particularities of the process depend on the type of camera. Probably we should manually repeat this process once an hour if we want to ensure the measurements are correct.
Then, I must constantly keep an eye on the thermal camera?
For most cameras, yes, indeed. Nevertheless to avoid both the periodic manual readjustment and keeping an eye on the device, our cameras come together with what we know as “blackbody”.
The “blackbody” is a device that is designed and built to emit a controlled thermal radiation. It is placed in the camera field of vision in an area where it does not interrupt the normal flow of people, conveniently mounted –for example on another tripod- and it enables the camera to automatically take a reference calibration.
