Fever screening thermal camera Q & A
Using the unique function of measuring the temperature of a moving object, we can separate a suspected
person of having a fever from other people. This is called fever screening.
After separating a suspected person of having fever, we measure the temperature of inside ear using
portable thermometer to finally determine if it is a real fever or not.
This article is about frequently mentioned questions and answers using IRXP6000 fever screening thermal
camera and One Channel Analyzer.
1. Human body temperature
A person’s normal body temperature can vary depending on their gender, age, measurement time
of a day, etc., from 35.8 to 37.2 degrees Celsius is called normal body temperature. Of course, it’s
a little different depending on the body’s area of measurement, and in order to accurately measure
body temperature, we measure the temperature in the armpit, mouth, anus, or the ear.
Normally, if your body temperature is above 37.5 degrees, you will be judged to have fever
.===➔ Normal body temperature varies depending on the person. The normal body
temperature range is about 1.4 degrees.
2. Temperature of face
The Fever scouring thermal camera does not measure the temperature of the armpit, mouth,
or the ear, but it should measure the temperature of the face of a person on the move.
So, is the temperature of a person’s face proportional to his or her body temperature?
===➔ The principle of measuring the temperature of a person’s face with a thermal camera is that
infrared rays radiated from a person’s face are transmitted through a lens to each pixel of the
thermal camera sensor, and each pixel is slightly heated to vary its electrical characteristics, and
electrical output each pixel of the sensor is processed through a unique algorithm to obtain thermal
images and also get a temperature value.
3. When measuring the temperature with a thermal camera, does the temperature value differ
depending on how far the subject has apart from the camera?
When measuring temperature of an object with a thermal camera, many ask whether it is measured
differently depending on the distance from the camera to the object. Depending on the efficiency
of processing algorithms developed by the camera manufacturer and how sophisticated the
temperature correction was in the production process, the temperature difference by distance from
camera to the object varies greatly.
In fact, the thermal imaging camera used for temperature measurement was used at a fixed distance
in most cases, so no one took issue with the difference in temperature measurements in different
However, in the case of Fever scouring thermal cameras used to measure the face temperature of
people on the move, we need to accurately measure the face temperature of people on the move
in the range of about 5-10 Meters, so we need to adopt a special algorithm to suit this purpose
and make accurate temperature correction..
4. Why is SPI’s IRXP6000 thermal camera suitable for Fever Screening?
COX thermal imaging cameras for fever screening are all in the range of +/-0.5 degrees when a
person stands 1m, 5m, and 10m away from the camera and measures the temperature of the face
temperature. To do so, a specially developed algorithm was adopted for fever screening, and the
camera was specially calibrated during camera manufacturing process.
5. How do I set the alarm reference temperature?
Fever screening thermal camera gives an alarm signal when it detects a person suspected of having
fever. When the alarm is triggered, the wave file selected in advance plays, the outer edge of the
ROI glitters, the maximum temperature indication on top of the ROI glitter, and the LED strobe
on the camera glitters. As soon as the alarm outputs, the operator look at the monitor and can
recognize who caused alarm, who has the most red on his face(Person with maximum temperature
marked next to face), and call the person to measure the temperature with a portable thermometer
to determine if he has Fever or not.
The important point is how much the alarm reference temperature should be set. If this temperature
is set too low, too many people are screened out and we have to measure the temperature in the
ear with a portable thermometer, which makes it less efficient.
With five normal body temperature people facing the camera at a distance of 3 meters, measure
the temperature with the camera, and set the alarm temperature at 0.5 degrees higher than the
second highest temperature, except for the highest person among the five people. If too many
people are screened in operation, raise the alarm setting temperature by 0.1 degrees to find the
6. Zero-Offset feature
The temperature of a person’s face measured by a Fever screening thermal camera is between 32°C
and 34 °C, much lower than the actual body temperature. From the perspective of the operator
who manages fever screening operation, it feels strange because it is much lower than actual
human body temperature. If the operator wants the human face temperature to be displayed in
numbers similar to the actual body temperature, raise the Zero-Offset by 3 to 4 degrees in the One
Channel Analyzer program. If operator increase Zero-Offset by 3 degrees, face temperature(between
32°C to 34°C, according to ambient temperature) shall be expressed 35°C to 37°C.
7. ROI(Region of Interest) and false alarm
After installing the camera, the user should set the most suitable ROI(short for Region of Interest).
Cameras check temperature of each pixel in the ROI and express those pixels exceeded set
temperature in set color(default color is red), and outputs alarm signal.
If an object on the ceiling or on the wall with a constant temperature higher than set temperature
is located inside ROI, it will cause false alarm, and we have to excluded such object.
Since installer set standard ROI in the polygon type ROI before hand over to user, the end user
must re-adjust ROI to exclude any objects whose temperature are higher than the human face
temperature before start fever screening work, not to have false alarm.
9. When alarm is generated, how can we know which person in the image is suspected person
of having a fever?
When One Channel Analyzer outputs alarm, a wave file (Siren) is played and LED strobe is glittering.
Operator is requested to see monitor to recognize who caused alarm.
The maximum temperature is displayed on the face marked with a lot of red, and operator must
call the person in to accurately measure the temperature of the body with a portable thermometer
to determine if the person has fever or not.