OK WMFT, I can understand it being calibrated for sensitivity level, but that's not what I was discussing in my post.
I see no way the meth gun can read a concentration level. As a handheld device, it can detect the presence of a substance if that substances fluorescent intensity is above the calibrated sensitivity threshold, but it cannot determine the concentration.
It is qualitative not quantatative.
I've talked with two companies both manufacturing handheld, stand-off, trace detection devices and both have told me it can't be done. One said it can be attempted with special attachments to the front of the device, but even then the accuracy is no where near that of a bench-top equivalent and it's a hassle to calibrate.
That's why I was puzzled by Poteet's remark about detecting low levels that would not hold up as evidence or warrant a police search.
My understanding is that it either detects a presence or it does not.
Red light, green light.
