IR Camera Sensors: Microbolometer Specs, Decoded
Two thermal cameras can carry nearly identical marketing copy and differ tenfold in price. The gap almost always traces back to one component: the detector. Nearly every uncooled infrared camera sold today — from a $250 phone clip-on to a $12,000 industrial unit — reads the scene with a microbolometer array. Once you know what a microbolometer measures and how its four core specs behave, the spec sheet stops being a wall of numbers and starts telling you exactly what you are paying for.
What the sensor actually measures
A microbolometer does not “see” heat the way a normal camera sees light. Each pixel is a microscopic bridge of silicon nitride, suspended a few micrometers above the silicon readout chip over a vacuum gap that thermally isolates it. On top of the bridge sits a thin film of vanadium oxide (VOx) or amorphous silicon (a-Si). Long-wave infrared from the scene passes through a germanium lens, lands on the bridge, and warms it a fraction of a degree. That warming changes the film’s electrical resistance, and the readout integrated circuit (ROIC) underneath converts the resistance shift into a temperature value for that pixel, dozens of times per second.
The array is uncooled — no cryogenic cooler, no bulky housing — which is the entire reason handheld thermal imaging is affordable. Cooled sensors exist and outperform microbolometers for extreme temperatures, but they belong to research and defense budgets. For building, electrical, and HVAC work, an uncooled microbolometer is the correct tool. If the underlying physics interests you, our explainer on how thermography works covers emissivity and the way objects near room temperature radiate.
VOx versus amorphous silicon: does it matter to you?
The two sensing films split the market. Vanadium oxide has a higher temperature coefficient of resistance — roughly 2 to 3 percent per kelvin — so it produces a stronger signal per unit of absorbed heat and has anchored higher-end cameras for two decades. Amorphous silicon runs a slightly lower coefficient but fabricates on standard silicon lines, which lowers cost and has let it close much of the performance gap.
Here is the honest takeaway for a buyer of a finished camera: you rarely get to choose the film, and it should not drive your decision. The published resolution, NETD, and refresh rate already fold in whatever the material contributes. Chase those numbers, not the chemistry.
Resolution: how many real thermal pixels
Resolution is the native pixel count of the array — and it is the number vendors most often blur with software “enhancement.” Insist on the true detector resolution, not an upscaled figure.
| Array | Pixels | Typical fit |
|---|---|---|
| 80×60 | 4,800 | Phone accessories; spots obvious anomalies only |
| 160×120 | 19,200 | Routine residential walkthroughs |
| 256×192 | 49,152 | Strong prosumer value tier |
| 320×240 | 76,800 | The working standard for serious inspection |
| 640×480 | 307,200 | Predictive maintenance; small or distant targets |
Resolution governs how much detail survives at a distance. A 320×240 sensor aimed at an electrical panel from one meter lands several pixels on each breaker; back up to three meters and each breaker collapses onto a pixel or two, hiding the loose-connection hot spot you came to find. More pixels buy you working distance and finer detail — nothing else. Each step up the ladder roughly doubles pixel count and, in the same product tier, roughly doubles sensor cost, which is why prices cluster at these fixed rungs. Our breakdown of what a thermal camera costs tracks that ladder tier by tier.
NETD: the number that separates good from great
Noise-equivalent temperature difference (NETD) is the smallest temperature change the sensor can distinguish from its own electronic noise, quoted in millikelvins. Lower is better. A camera rated at 40 mK resolves finer thermal contrast than one at 120 mK, all else equal.
- 100–200 mK — entry consumer clip-ons
- 50–100 mK — mid-tier consumer and prosumer
- 30–60 mK — professional inspection cameras
- under 30 mK — research and high-end industrial
Context keeps this honest. Most building defects shout: missing insulation, a wet substrate, or an overloaded breaker throws a signature of 1 to 5 °C — that is 1,000 to 5,000 mK against the background, so even a 150 mK sensor catches it easily. NETD earns its keep on the subtle jobs: predictive-maintenance trending where a bearing warms two degrees year over year, or a faint loose-connection signature that has to stand out from a busy panel. For general inspection, aim for NETD under 50 mK if the budget allows and stop worrying below 30 mK unless the work truly demands it.
Pixel pitch and the two directions the market is moving
Pixel pitch is the center-to-center spacing between pixels. Early arrays used 25 to 50 micrometers; 17 micrometers is today’s dominant size, and 12-micrometer arrays are the emerging generation. Shrinking pitch does one of two things depending on the design goal: hold the array physically the same and you fit more pixels (higher resolution), or hold the pixel count the same and you get a smaller, lighter, cheaper camera. Both are happening at once, which is why 12-micrometer pitch is quietly spreading across the upper-consumer and lower-professional tiers. Once resolution and NETD are fixed on the spec sheet, pitch tells you more about the camera’s size and price than about its image quality.
Refresh rate and the 9 Hz line
Arrays read out anywhere from 9 Hz to 60 Hz. The 9 Hz cap on many consumer cameras is not an engineering limit — it is an export-control artifact, since faster thermal video historically triggered U.S. licensing over military and surveillance concerns. Practically, 9 Hz looks choppy when you pan quickly but is perfectly fine for the steady, aim-and-capture rhythm of an inspection. Reserve 30 Hz or 60 Hz for tracking moving targets or for smoother client-facing walkthrough video.
Spectral band: why it is long-wave
Microbolometers respond in the long-wave infrared band, roughly 7 to 14 micrometers — the wavelengths where room-temperature objects radiate most strongly. The germanium lens is chosen precisely because it passes this band while blocking visible light. Mid-wave cooled sensors (3 to 5 micrometers) win for targets in the thousands of degrees, but for anything you would inspect in or around a house, long-wave is the right band.
The spec sheet is not the whole camera
Two cameras with matching detectors can still produce different images, because the sensor is one link in a chain. The germanium lens — its element count, coatings, and f-number — sets how sharply infrared even reaches the array; a top sensor behind a mediocre lens loses to a modest sensor behind a good one. The ROIC’s noise floor, the non-uniformity-correction shutter that briefly closes to recalibrate, and the image-processing firmware all shape the final picture independent of raw pixel count. When two units quote the same resolution and NETD at very different prices, the gap is usually hiding in the optics and processing.
Matching sensor to the job
For the majority of home and building inspection, a 320×240 array with NETD under 100 mK, 17-micrometer pitch, and 9 Hz refresh does the work without waste. Step up to 640×480 when targets are small or you need to shoot from a distance — rooftop equipment, tall panels, distribution gear. Drop to 160×120 for casual homeowner use where finding the obvious matters more than resolving the subtle. The detector technology is identical across the tiers; what you are really buying up the ladder is array size, a lower noise floor, better glass, and smarter firmware. For a curated look at current models, see our roundup of the best thermal imaging cameras, or start from the broader home inspection tools hub.
Frequently asked questions
Is a higher-resolution sensor always worth the extra cost?
Only if your targets are small or far away. Resolution buys working distance and fine detail. If you inspect residential interiors at arm’s length, a 256×192 or 320×240 sensor already resolves everything a defect will show; paying for 640×480 mainly helps predictive maintenance and elevated or distant equipment.
Does the sensing material — VOx or amorphous silicon — change the images I get?
Not in a way you can shop for. The film influences the sensor’s raw signal and noise, but the manufacturer has already baked those effects into the published NETD and resolution. Compare cameras on those numbers rather than on the underlying chemistry.
Why do some cameras advertise a much higher resolution than their detector?
They are quoting a software-upscaled or blended figure, not native detector pixels. Interpolation smooths the display but adds no real thermal detail. Always confirm the true array resolution — the honest spec sheets list both.
Do I need infrared certification to use one professionally?
No license is federally required to operate a thermal camera, but trade credentials matter for reporting and liability. Organizations such as InterNACHI offer infrared thermography training that lenders and clients recognize.
This guide draws on public technical guidance from the U.S. Department of Energy on thermographic energy audits and from OSHA on electrical inspection safety.