I bought the HT-19 handheld imager. The only thing I do not like is it always auto ranges so you will always see the full-color range on the screen. I'm not sure if this model allows manual ranging but that is something I would look for next time.
Good question, I don't know which model lets your spanlock / manual lock a given range, and also been looking at Ht301/T3S, but it's not like they've gotten cheaper after all these years.. recall they were just below 500 US bucks 3 or 4 years back when different Chinese forums reps tried to push them to buyers on different forums, not least here on EEVblog.
The Dongle units with 192x256 microbolometer are on the other hand. getting quite low in price & common.. saw one yesterday at AliE for below 200 USD with a 192x256 sensor and that price at just under 200 US was even with incl. 25% danish VAT and shipping.. but sadly a unit with a fixed focus (not adjustable).
The span range lock, is a feature I use all the time, as otherwise, It will often blow out the small temp/thermal variables I wanna see in pictures or video.
and I would also like some info, on to what extent you have that on fx the apps for Hti301, T3, T3S, T3pro, T2, T2S, T2L, T2 Pro etc, alongside a shutload from other brands, that mostly is 256x192 or below microbolometers and often very limited information about the app..
I remember' I heard that there is quite a difference between T3S, Hti301, T3, T3pro and the app for these 384x288 dongles, versus the models below, like 2-series that should be quite limited.
For these thermal dongles, the app. plays such a huge role, so crucial to get an idea of what possibilities it gives.
On the old Seek Pro FF it's mostly the Tyrian palette I prefer, and the span lock, so I can lock out the things I'm not interested in.
Also the approach I have been using on pictures like these, where I try to drown out the background and lock the span-range...