Optris PI 400i, Xi400 Technical Note

TECHNICAL NOTE - FEVER SCREENING SYSTEMS

37,2°C

Viral epidemics like the current coronavirus / COVID-19
create a worldwide demand for infrared cameras able to
screen for a fever condition in humans.

Our product portfolio comprises two infrared cameras
dedicated to this application:

Xi 400 with T010 range (-20…100 °C)

PI 450i with T010 range (-20…100 °C)

Both cameras sold with certifi cates of calibration validating

measurement made against traceable 35 °C temperature
reference source.

The basis for the eff ectiveness of thermal cameras as a

screening tool lies in the correlation of outside skin
surface temperature with internal or core body
temperature.

There are basically two main approaches

1. Crowd based screening

The IR camera is monitoring a crowd of people at once or

sequential. Assuming that the majority of the measured
maximum head temperature values are coming from healthy
individuals the exceptions with an elevated body

temperature can be easily detected.

Recommendations:

Xi 400 T010 or PI 450i T010

with 29° or 53° optics ≥ 4 m distance

Xi 400 T010

PI 450i T010

2. Individual screening

This method is mainly used at control gates or where
crowd screening is not possible. The Medial Canthus
(tear duct) provides the strongest correlation between
outside skin temperature and core body temperature
and is measured more precisely from a close distance.

This method is also best for detecting low grade fevers.

Recommendations:

PI 450i T010 with 29° optics @ 1 m distance or
PI 450i T010 with 13° optics @ 1.5...2 m distance

(MFOV should be 4 mm or less)

37,2°C

37,2°C

Absolute temperature measurement accuracy

Most IR cameras with 8-14 µm spectral response are specifi ed with an accuracy of +/- 2°C or 2% of reading
whichever is greater based on deployments in industrial environments in a wide variety of ambient conditions
from 0 °C to 50 °C.

Many IR cameras with microbolometer sensors are promoted today with accuracies of +/- 0.5 °C or better. These accuracies
cannot be achieved without the use of a black body reference source. The source needs to be stable, have high emissivity

and positioned in the scene proximate to the subject to be scanned.

Our BR20AR ambient referencing source can be combined with our PI 450i T010. The black body is equipped with a 16 bit
digital temperature sensor with +/- 0.1 °C accuracy. By integrating this highly accurate reference signal to our PIX Connect
software, we can reduce camera uncertainties resulting from device adjustment, ambient temperature drift and short term
stability down to a system accuracy of +/- 0.5 °C with a confi dence interval of 95%.

The real ability of an IR camera based screening system to detect subjects with fever lies more in the ability to discern which

external face temperatures, as measured at the tear duct/ Medial Canthus, are signifi cantly higher than those in a given
population exposed to similar ambient temperature conditions.

Best measurement at
Medial Canthus

optris BR20AR

with bracket for ceiling or wall mount

IR temperature measurement at the Medial Canthus for a close correlation to the core body temperature