Check the sensor first. A FLIR Lepton 3.5 measures 160 × 120 points; advertised 1440 × 1080 or 640 × 512 images are computed.
Data-led guide
Smartphones with a built-in thermal camera
A rugged phone with a built-in thermal camera saves carrying an extra module or camera. But on these devices the advertised resolution is rarely the sensor's: this guide separates what is measured from what is computed.
Be wary of "AI" resolutions. When a manufacturer credits its resolution to an algorithm, the number of pixels really measured is unknown.
Compare with a module. For the same budget, a smartphone module often publishes a native 256 × 192 sensor, a NETD and a measurement range.
The six documented thermal phones
Listed alphabetically: without a score, no order of merit is implied. "Not published" means the value is not reliably available; it is never estimated.
| Phone | Sensor | Native resolution | Advertised resolution | NETD | Range | Weight | Price band |
|---|---|---|---|---|---|---|---|
| AGM G3 Pro | not published | not published | 512 × 384 | not published | -20 to 550 °C | 375 g | €€€ |
| Blackview XPLORE 1 Pro | FLIR Lepton 3.5 | 160 × 120 | — | 50 mK | -10 to 400 °C | 640 g | €€ |
| Cat S62 Prodiscontinued | FLIR Lepton 3.5 | 160 × 120 | 1440 × 1080 | not published | -20 to 400 °C | not published | €€€ |
| Ulefone Armor 27T Pro | FLIR Lepton | 80 × 60 | — | not published | -10 to 450 °C | 441 g | €€ |
| Ulefone Armor 28 Ultra Thermal | ThermoVue T2 | not published | 640 × 512 | 40 mK | -20 to 550 °C | 450 g | €€€€ |
| Ulefone Armor 29 Pro Thermal | ThermoVue T2 | not published | 640 × 512 | not published | not published | 688 g | €€€ |
What advertised resolutions hide
Three spec sheets raised problems. Ulefone presents the Armor 29 Pro Thermal's 640 × 512 as the output of its SharpenAI algorithm: a computed image. For the Armor 28 Ultra Thermal, the official spec sheet states the same 640 × 512, but the same manufacturer's product page mentions a resolution 2.56 times higher than the previous generation, which does not add up. At AGM, the 512 × 384 stated for the G3 Pro is incompatible with the published focal length and field of view. In all three cases the native resolution is shown as not published and the advertised value is kept as the displayed resolution.
Thermal phone or module?
The thermal phone offers ruggedness (IP68, IP69K, military standards), battery life and nothing to plug in. The module offers better-documented measurement specs, a lower price and the freedom to keep your usual phone. For temperature measurement, a well-documented module remains the safer choice today; for field detection in harsh conditions, the rugged phone holds its own.