International Standard

There is an international standard for the performance & accuracy of human temperature measurement provided by astm.org. For full details please refer to www.astm.org/Standards/E1965.htm.

"The specification addresses assessing subject’s body internal temperature through measurement of thermal emission from the ear canal. Performance requirements for non contact temperature measurement of skin are also provided."

"This specification covers electronic instruments intended for intermittent measuring and monitoring of human temperatures by means of detecting the intensity of thermal radiation between the subject of measurement and the sensor."

The key to successful human body temperature measuring is the accuracy and this is given in the above standard as +/- 0.3°C.

The Thermal Technology

The optimum wavelength range of an un-cooled Thermal Camera for the detection of body temperature within humans should sit in the region of around 7 µm to 14 µm range, which is referred to as the Long Wavelength Infra-Red (LWIR) range

The Dahua DH-TPC-BF2221-HTM1, BF5421, BF3221 Thermal Network Bullet cameras are optimised to use LWIR to deliver accurate results.

The Dahua DH-TPC-BF3221, BF5421, BF2221P Thermal Network Bullet cameras are designed to work with the Dahua WizSense® and WizMind® recorders & DSS Express and are additionally integrated with the Luxriot EVO VMS including temperature and Black Body error alerts.

 

  • Series 5 Thermal Camera

    DH-TPC-BF5421-TE

    Dahua 5MP Pro AI Vari-focal IR Bullet Network Camera
  • Series 2 Thermal Camera

    DH-TPC-BF2221-HTM

    Dahua 5MP Pro AI Vari-focal IR Bullet Network Camera
  • Black Body Reference

    DH-TPC-HBB

    Dahua Black Body Reference

DH-TPC-BF5421-T THERMAL SENSOR

300 x 400 VOx Uncooled Thermal Sensor Technology

Athermalised Lens, Focus-free

13 mm Fixed Thermal Lens

≤ 40 mK Thermal Sensitivity

Accuracy: +/- 0.3 °C

Spectral Range: 8µm - 14µm

DH-TPC-BF5421-T VISIBLE SENSOR

1/2.8-in. 2 MP Progressive-scan CMOS Sensor

8 mm Fixed Lens

Maximum IR Distance 35 m

DH-TPC-BF5421-T SYSTEM

Active Alarm

Support ROI, Motion Detection, and Color Palettes

Enhanced Power and Data Transmission Distances (ePoE)

IP67 Ingress Protection

DH-TPC-BF2221-HTM THERMAL SENSOR

256x192 VOx uncooled thermal sensor technology

Athermalised Lens, Focus-free

F1.0 3.5 mm/7mm Fixed Thermal Lens

≤ 50 mK Thermal Sensitivity

Accuracy: +/- 0.3 °C

Spectral Range: 8µm - 14µm

DH-TPC-BF2221-HTM VISIBLE SENSOR

1/2.8-in. 2 MP Progressive-scan CMOS Sensor

4mm/8mm Fixed Lens

Maximum IR Distance: 4mm - 35 m; 8mm - 50m

DH-TPC-BF2221-HTMSYSTEM

Active Alarm

Support ROI, Motion Detection, and Color Palettes

Enhanced Power and Data Transmission Distances (ePoE)

IP67 Ingress Protection

Black Body Reference

Default calibration temperature: 35.0 °C

Range: Ambient temp.+5.0 °C to 50.0 °C

Effective radiation surface: 70 mm x 70 mm

Resolution: 0.1 °C

Accuracy: +/- 0.2 °C

Noise Equivalent Temperature Difference

NETD is a measure for how well a thermal imaging detector is able to distinguish between very small differences in thermal radiation in the image. It is sometimes referred to as "Thermal Contrast" and is expressed as milli-Kelvin (mK). The lower the NETD value the better the temperature measuring accuracy.

The Series 2 cameras have an NETD value of ≤ 50mK, whereas the Series 5 cameras are better with an NETD value of ≤ 40mK.

NETD will be specified together with the F-Stop, e.g. ≤ 40mK @F1.0

netd_40mK
netd_50mK

Thermal Optics

As with all CCTV the lens function is also very important, the use of better optics such as germanium lenses with F-Stop of F1.0 will produce better and consistent results when measuring human body temperature. " A Germanium lens is a special lens, where visible rays cannot pass through it and it appears to be black to the physical eyes.". Germanium coated lenses ensure optimum transmission of heat through the required temperature range.

VOx Sensor Material

Vanadium Oxide (VOx) is the most sensitive material available for detecting longwave radiation. VOx thermal sensors do not have the image distortion characteristics often associated with more commonly used and low-cost materials, such as Amorphous Silicone (a-Si).

  • Higher photoelectric conversion efficiency
  • Higher Signal to Noise ratio
  • Strong light protection facility
  • Good temperature stability
thermal_image_vox
thermal_image_asi

Sensor Resolution

And finally resolution, like all CCTV cameras, thermal imagers have pixels. Modern IP visible cameras have 4 or even 8 million pixels, thermal cameras though are typically much lower 400x300 (120,000 pixel) down to 160x120 (19,200 pixel). The higher pixel count sensors will deliver more accurate results, whereas lower resolution sensors may not pick up abnormal temperatures so accurately as there are less points of reference.

Thermal Camera Accuracy - use of a Black Body reference

The thermal camera is a critical part of the human temperature measuring solution but also important is environment where the equipment is installed and the use of a thermal reference point. Thermal references such as the Dahua Black Body deliver a constant and extremely accurate temperature reference enabling the thermal camera to maintain accurate and real time calibration. Without a Black Body unit in the field of view of the thermal camera, such as the TPC-HBB-AHW, the camera has no accurate reference and therefore cannot be relied on for accurate human temperature monitoring.

Accuracy of within 0.3°C is only possible when the thermal camera is used with the black body and when the environment temperature is between 10°C to 30°C (50°F to 86°F). The use of fever screener BTM cameras can be an important part of an overall safety strategy businesses can take to help combat the spread of Covid-19, the use of properly configured systems that have been carefully designed to work reliably 24/7 remains an very important consideration when choosing your BTM solution. The use of systems without a Black Body is not recommended for accurate contact free thermal temperature monitoring.

Dual Sensors, Artificial Intelligence & AI algorithms

Using the visible light sensor, with 1080P resolution, the AI algorithms are used to detect the presence and location of a person’s face. The AI is further used to detect temperatures in known facial "temperature hotspots" such as the inside area of the eyes near the nose, around the side base of the nostrils and forehead. It is recommended that persons remove their glasses as they can block thermal energy and may produce lower accuracy readings.

Each of the Dahua Thermal Cameras for human temperature monitoring (Series 2, Series 3 & Series 5 ) have the same dual camera technology.

Key Specification Parameters for Optimum Performance

  • Vanadium Oxide VOx uncooled detector: Detector Type: Better Material = Better Sensor & Accuracy.
  • Effective Pixels 400x300: Pixel Resolution: More Pixels = Better Accuracy.
  • Use of Black Body Reference: Required to deliver accurate results.
  • Spectral Range 8-14 µm: Human Wavelength Range.
  • Thermal Sensitivity ≤40mK @ F1.0: Lower NETD= Better Accuracy
  • Wider Germanium Coated lens: Lower F-Stop = More Light, Improved Accuracy
  • Fixed 13mm Focal Length: Focal Length; Bigger = Closer view of the face, Higher Accuracy
  • Effective Artificial Intelligence Algorithms to recognise and pinpoint key areas of the face

Data Sheets

DH-TPC-BF2221-HTM 2 series Thermal Camera
DH-TPC-BF5421-T 5 series Thermal Camera
DH-TPC-HBB Black Body

Comparing Camera Technologies Dahua Series 5 vs Series 2

Dahua TPC-BF2221-HTM Series 2
Thermal Specification
Detector Type Uncooled VOx Focal Plane Detector
Effective Pixels 256 (H) x 192 (V)
Pixel Pitch 12 µm
Spectral Range 8 µm to 14 µm
Thermal Sensitivity (NETD) ≤50 mK
Focal Length 3.5 mm & 7mm
Field of View 3.5mm 50.6° (H) x 37.8° (V)
7mm 24° (H) x 18° (V)
Focus Mode Fixed Focal, athermalised
Aperture F1.0
Temperature Accuracy ±0.3° C, with blackbody
±1° C, without blackbody
Dahua TPC-BF5421-T Series 5
Thermal Specification
Detector Type Uncooled VOx Focal Plane Detector
Effective Pixels 300 (H) x 400 (V)
Pixel Pitch 17 µm
Spectral Range 8 µm to 14 µm
Thermal Sensitivity (NETD) ≤40 mK
Focal Length 13 mm
Field of View 30.0° (H) x 22.60° (V)
 
Focus Mode Fixed Focal, athermalised
Aperture F1.0
Temperature Accuracy ±0.3° C, with blackbody
±1° C, without blackbody

Setting up

Dahua Thermal Imaging
 


YouTube demonstration video of BTM in action.

  • The installation area needs to be relatively isolated and stable environment without wind, avoiding outdoor conditions or any scene in the background connected with the outdoor. Human Body temperature Measurements are not suited to installation environments with high air flow or strong electromagnetic interference or vibration.
  • The installation area shall ensure that the moving direction of the flow of people is facing the camera in a positive direction to ensure that the camera can detect the temperature of the face and forehead.
  • Do not place high temperature heat sources or sunlight within the thermal image , always avoid the possible interference of external unwanted heat sources such as microwave oven, heater, hot water dispensers, high-power lamp, radiator, etc ,to avoid damage to the detector.
  • The visible light channel of the binocular camera requires sufficient illumination in the environment have a neutral background without the influence of backlight/reflection/change of strong light for example from doors or windows.
  • It is recommended to use the flow direction guide device (protocol bar, etc.) to guide the walking direction of the personnel and control the width of the personnel aisle so that the personnel can face the thermal imaging camera at the best detection position.
  • When persons are entering from outside, they may have elevated temperature due to exercise, recently being in direct sunlight, using a flow control system allows body temperature to naturally settle.