The Sharx Security SCNC3905 (and SCNC3905-GRAY) cameras have a connection box that allows optional devices to be connected. One such device is the Sharx MD2XT dual tech motion detector.
This device uses microwaves like a police radar gun, together with passive infrared body heat detection, to make sure that the detected motion is caused by a person, large animal, or motor vehicle.
Shadows, insects, snowflakes or raindrops do not trigger the motion detection, either because they don’t have enough of a surface to reflect microwaves or because they have no body heat.
If you need this kind of professional reliability for motion detection, the MD2XT can be ordered from the Sharx Security web site, in the accessories section. It comes with 2 ft of 4 conductor wire, and you can substitute your own 4 conductor low voltage wiring, for example using standard telephone wire or even network wire.