Phil L wrote:
RzB wrote:
Many thanks to all for the responses.

One other point - The Distance:Spot ratio. Do I take it that's
the size of the area being measured vs. distance from surface?
So if it's 8:1 then if you are 8 metres away from the surface
it's measuring a 1 metre diameter area.

Many thanks,
Roy

No, it's in mm, you can be 800mm away and get a 100mm feild in which
readings can be taken, sort of like a torch beam.

It won't pick up anything from 8 metres away because it's over 26 feet.

It's not like a torch beam, when the farther away you get, the dimmer
it gets on the thing you're shining it on, till eventually you can't see
it.

The building (or whatever) shines in the infrared - and all that happens
as you back away is that you measure more area.
It doesn't get dimmer.
(until you get a few kilometers away, or it's foggy, in which case the
air starts to absorb a fair bit)