What camera specification primarily determines the smallest detectable temperature difference?
A) IFOV
B) NETD
C) Resolution
D) Frame rate
Answer: NETD (Noise Equivalent Temperature Difference)
What is NETD?
NETD (Noise Equivalent Temperature Difference) is one of the most important specifications in an infrared (thermal) camera. It represents the smallest temperature difference that the camera can detect above its own noise level.
- Measured in millikelvin (mK)
- Example: A camera with NETD = 50 mK (0.05°C) can detect very small temperature differences
- Lower NETD = better sensitivity
In simple words:
- NETD tells you how “sharp” the camera is at detecting tiny temperature variations.
Why NETD is the Correct Answer
When you are doing thermography, especially in applications like:
- Electrical inspections
- Building diagnostics
- Predictive maintenance
You often need to detect very small temperature differences (like 1–2°C or even less).
- Only NETD directly defines this capability.
Why Other Options Are Incorrect
A) IFOV (Instantaneous Field of View)
- Defines spatial resolution (how small an object you can see)
- Does NOT determine temperature sensitivity
- Important for seeing small objects, not detecting small temperature differences
C) Resolution
- Refers to number of pixels (e.g., 320×240, 640×480)
- Higher resolution = clearer image
- But it does NOT improve thermal sensitivity
D) Frame Rate
- Indicates how many images per second the camera captures (e.g., 9 Hz, 30 Hz)
- Important for moving targets
- No impact on temperature detection capability
Practical Example
Imagine inspecting an electrical panel:
- Faulty connection temperature: 45.2°C
- Normal connection temperature: 45.0°C
- Difference = 0.2°C
- A camera with low NETD (e.g., 40 mK) → will detect this difference
- A camera with high NETD (e.g., 150 mK) → may miss it
