The principle and accuracy of thermal imaging temperature measurement: what can and cannot be done
Explain the working method and influencing factors of thermal imaging temperature measurement, and clarify the misunderstanding and correct use method of "non-contact temperature measurement must be accurate".
Principle
All objects above absolute zero will radiate infrared rays. The higher the temperature, the stronger the radiation. Thermal imaging cameras receive this radiation via infrared detectors and convert it into a temperature distribution image (heat map), Then combined with emissivity and other parameters, the surface temperature of the measured object can be calculated.
It needs to be emphasized: Thermal imaging measures the surface temperature of an object, not the internal temperature, nor the ambient temperature.
Factors affecting accuracy
| Factors | Influence | Coping |
|---|---|---|
| Emissivity setting | Different materials vary greatly, and setting errors will lead to significant deviations | Calibrated according to material, commonly used is 0.95 |
| Measurement distance | The farther the distance, the greater the impact of atmospheric attenuation and pixel ratio | Follow the D:S ratio and try to get as close as possible |
| Environmental reflection | The surrounding high-temperature objects reflect to the measured surface | Avoid heat sources, or perform reflection temperature compensation |
| Wind and airflow | Accelerate surface heat dissipation, readings are low | Set up wind shelters |
| Dirty lens | Occlusion will directly lead to abnormal readings | Clean regularly |
| Device drift | Drift due to long-term operation | Enable automatic correction (shutter) |
What can be done
- Equipment overheating warning: Temperature abnormality monitoring of distribution cabinets, transformer joints, and cable joints, This is the most mature application in industrial scenarios.
- Fire prevention warning: Early detection of abnormal temperature rise in warehouses, stockyards, and forest areas.
- Night intrusion detection: Does not rely on visible light, penetrates smoke and partial occlusion.
- Perimeter prevention: Use visible light for double detection to significantly reduce false alarms.
What not to do
- Medical standards that cannot replace human body temperature measurement: The accuracy of ordinary thermal imaging (±2℃ or ±2%) is not enough for medical screening. For human body temperature measurement, special blackbody calibration and higher-precision equipment are required.
- Cannot penetrate glass: Ordinary glass is opaque to infrared, and the true temperature cannot be measured through the glass.
- Cannot measure internal temperature: Can only measure surface temperature.
Deployment Points
- When selecting, focus on resolution (160×120 / 384×288 / 640×512) and thermal sensitivity (NETD, the smaller the better).
- The temperature measurement type and the imaging type are different products. If you need to measure temperature, you must choose the temperature measurement type and have a blackbody calibration interface.
- The installation should be away from direct sunlight and air conditioning outlets.
- Set multi-level thresholds: early warning, alarm, emergency, and cooperate with platform push.
Related content
What is an IPC network camera? What is the difference from analog cameras
08-29
How to choose surveillance camera resolution: 2 million, 4 million, 8 million pixels
08-27
How to choose camera lens focal length: 2.8 / 4 / 6 / 8 / 12mm field of view comparison
08-25
What is wide dynamic range (WDR)? Why must backlight scenes be turned on?
08-23
Low-light and starlight cameras: how 0.001Lux is achieved
08-21
The principles, effective distance and common misunderstandings of infrared night vision
08-19
The relationship between code stream, code rate and frame rate and setting suggestions
08-17
How to calculate monitoring storage capacity: comparison of resolution, bit rate and storage days
08-15