NETD, Pixel Size and Field of View: Reading Thermal Module Specifications
By Haihan Defence ·
Thermal datasheets contain several measurements that describe different parts of imaging performance. Reading them together is more useful than choosing a module by a single figure.
NETD describes thermal sensitivity
Noise Equivalent Temperature Difference, or NETD, describes the temperature difference corresponding to the detector’s noise under stated test conditions. A lower value generally indicates sensitivity to smaller thermal differences under comparable conditions. The modules listed here specify ≤40 mK at 25 °C and F#1.0.
Compare NETD figures only when the measurement conditions are comparable. NETD is not a statement of absolute temperature measurement accuracy. If your project requires quantitative temperature readings, ask separately about radiometric capability, calibration and the applicable accuracy specification.
Pixel size is one part of the optical system
The listed thermal modules use a 12 µm pixel pitch. Pixel pitch alone does not determine scene detail: detector resolution and focal length also matter. A small detector with a particular lens may provide a very different view from a larger detector using another lens, even when both share the same pixel pitch.
Field of view defines scene coverage
Horizontal, vertical and diagonal field-of-view values describe the angular scene coverage. At a fixed working distance, a wider field of view covers more of the scene. A narrower field of view concentrates the available pixels over a smaller area. Choose based on the scene you need to observe, rather than treating either configuration as universally better.
Check focus and output information
A minimum focus distance is another practical limit. The listed thermal configurations specify 2 m, which should be considered when planning near-field work. Also distinguish native detector resolution from the video output format; output conversion does not increase native sensor detail.
Use the datasheet as a design input
For a useful comparison, record detector resolution, pixel pitch, lens, field of view, NETD conditions, interface, supply range and mechanical dimensions in the same order. Confirm missing parameters with the manufacturer before finalizing the design.
Browse our imaging modules, read the 640 vs 384 comparison, or request the current datasheet.