I've got 3 argus 2s and have been disappointed with the range and consistency of the motion detection, side by side testing shows the same results. One min it can detect at 7m the next 2m, (never had anything close to 10m at 1.5 meters high). I wanted to know more about the hardware so had a quick tear down.
Argus 2 has a decent Excelitas LHI 968 PIR chip, no range specified in the data sheet but 100′ horizontal and vertical field of view. The sensor fits through the housing into what looks like a custom made Fresnel lens, I didn't have time to disassemble.
So if the performance isn't related to the software detection / trigger / sensitivity. Another likely focus point issue could be the lens optics not being good enough or not meeting our specific environmental setups. I suspect there is a trade off between range vs field of view vs type of detection wanted. Would be great if we could customise the software settings more or even swap out different lens inserts for narrow long range or wide short range use cases..