Several of my motion sensors also report occupancy. They seem to trigger at different times. Can someone explain the difference?
One example is the Centralite 3328-G.
Very easy to explain:
Motion: that gets detected when I walk into the area, the sensor detects changes (usual infra-red changes) in its field of view. If I stand still in the kitchen, motion will no longer trigger.
Occupancy: this type of sensor can detect changes in the area due to stationary object changes in its field of view. So in the above example, the motion sensor would kick in first, but once I stood still by the sink, then the occupancy sensor would kick in after a while.
Summary:
Motion = something is/has moved in the area.
Occupancy = something new is in the area that is not normally there.
Generally, @JohnBeMe 's description is correct.
However, "occupancy" has become a bit of a buzzword, to the point that what it means often depends on the device and/or manufacturer. Quite a few unscrupulous manufacturers are selling devices that claim to have "occupancy" sensors, but they really only have motion sensors. Often, the only difference between the "motion" and "occupancy" entities provided by these devices is the length of the cool-down period or the delay before they turn off.
Based on the product data sheet my guess is that "occupancy" is not true occupancy sensing on this device... it's just motion with some sort of delay.
Absolutely true, thank you for raising that issue.