GOYOJO GW340 · USB-C plug on top
Spark Pro
More than 5× the thermal pixels of Spark (256×192 vs 96×96). Small cracks, single pipes and loose wires stay sharp — the one to choose for a whole house.
Works with
How it works
- Plug it into the phone’s USB-C port.
- Open the free “THG Start” app.
- Scan slowly — the hottest and coldest spots are marked for you.
Specs (from the manufacturer)
| Thermal sensor | 256×192 (512×384 enhanced) |
| Refresh rate | 25 Hz |
| Field of view | 50° × 37.5° |
| Thermal sensitivity | 50 mK |
| Temperature range | −20 to 350 °C |
| Weight | about 21 g |
| App | THG Start (iOS, Android) |
In the box
- Thermal camera (USB-C)
Questions about Spark Pro
Which phones does Spark Pro work with?
USB-C phones: iPhone 15 Pro to iPhone 17 and Android 12 or newer. The base iPhone 15 and iPhone 18 aren't on the maker's list yet — email us before you order. The maker no longer includes a Lightning adapter, so iPhone 14 and older won't fit.
Can a thermal camera see through walls?
No. It reads the temperature of the surface it's pointed at. A pipe, a leak or missing insulation shows up only when it makes that patch of wall warmer or cooler than the rest — which it usually does.
Why 256×192 and not 96×96?
Each thermal pixel is one temperature reading. Spark Pro takes more than five times as many as Spark, so you can stand back and still see a single pipe, a small crack or which plug in a power strip is running hot.
What app does it use?
The free THG Start app for iPhone and Android.
What temperatures can it measure?
−20 to 350 °C (−4 to 662 °F), with 50 mK thermal sensitivity — it shows differences of a twentieth of a degree.
Can I return it?
Yes, within 30 days of delivery if it's unused and in its original packaging. If it doesn't work with a phone this page says it works with, we refund you in full, including return shipping.
Guides that use Spark Pro
How to read a thermal image: colors, reflections and emissivity
Purple here, orange there, a yellow blob you can't explain. What the colors on a thermal camera actually mean, the three things that fool almost everyone, and a five-minute routine for any suspicious spot.
October 23, 2026
How to find drafts and insulation gaps with a thermal camera
Drafts are hard to find by feel, because moving air spreads out before it reaches you. A thermal camera shows them as streaks on the wall and floor. How to find them in an afternoon, and which fixes are DIY.
October 23, 2026
Spark or Spark Pro? How to choose a phone thermal camera
Both plug into a USB-C phone and use the same app. The difference is how many temperature points they measure, and that decides how far back you can stand and still see the pipe.
October 22, 2026Buying guides
- A thermal camera for your iPhone 15, 16 or 17Plug-in thermal cameras for USB-C iPhones: which models fit, Spark vs Spark Pro, and what they find at home — leaks, drafts, missing insulation, hot outlets.
- Home check before you buy or rentWhat to check in a house or apartment before you sign: water and damp, drafts and insulation, wiring, the roof, pests — and a free printable checklist.
- Looking for a FLIR ONE alternative?FLIR ONE vs Spark and Spark Pro on a USB-C phone: thermal pixels, refresh rate, range and weight — and where FLIR is still the better pick.