So what scale is the pressure attribute using in this device? (I'm thinking mb if it's barometric)
Also what is the function of the presence attribute? I mean this isn't exactly meant to be used as a presence sensor in the classic sense is it?
I searched but couldn't find the answer... Thanx in advance!!
Caveat emptor - my observations are based on using this device with zigbee2mqtt (and not Hubiat). The raw pressure data is in mbar. Raw temperature data is in centrigrade and relative humidity is in %.
That information was added in a Hubitat driver from Markus. It was to indicate if the sensor had fallen off the zigbee network.
Thanx.... I initially got it as a humidity/temp sensor for upstairs hallway and noticed after install it had the pressure and presence stuff in it. I likely won't really find a use for the barometric pressure part of it...
Here's an example of the data that the device sends ...
That last_seen is in epoch time. So I'll bet that in Markus' driver he took the current time in epoch, subtracted the last_seen and if the outcome exceeded a particular value, marked the sensor as being "not present".
I don't really have a use for it either. However, I notice that anytime we have a storm pass over us, there are big changes in the barometric pressure for the sensor in my garage, but not the one in my closet.
probably because of ac removing humidity in the air within the house causing bp to be stable vs your garage (my guess anyway, i am probably wrong though)
I think it is because tropical storms are low pressure systems, and my garage is not as well insulated from the outside. My closet is also inside another room.
When we're in a storm, the pressure drops from ~1015 mbar to ~980-1000 mbar. Interestingly, the drop starts somewhat before the storm is directly above us.
I get this. Somewhat different than yours
Yeah - mine was the data into zigbee2mqtt from the sensor.
Seems odd. I would guess the sensor in the closet is not reporting pressure changes properly.
Is this a hermetically sealed room? You must have a very well sealed home/closet. I would expect the indoor bp to follow the outdoor (garage) bp, albeit with a lag and some offset.
@aaiyar my have that happen if he opened the doors to his home, let it warm up to outside temperature, then cool it way down, but it might cause the walls to collapse because the drop in temp would cause a drop in your interior volume (Ideal Gas Law: PV=nRT, or Charles’s Law of hvolumes: T1V1=T2V2).
Or @JohnRob was correct!!
@JohnRob has the most likely answer, but it’s fun to play “what if?”
Maybe the 
of the storm was in the garage, and the closet was far enough away to have a higher pressure?
The eye is a region of mostly calm weather found at the centre of strong tropical cyclones. The eye of a storm is usually circular and typically 25–40 miles (40–65 km) in diameter. It is surrounded by the eyewall , where the most severe weather of a cyclone occurs. The cyclone's lowest barometric pressure occurs in the eye, and can be as much as 15% lower than the atmospheric pressure outside of the storm.
Admittedly, it would need to be a VERY detached garage.
Would that be before the storm or after the storm?
Gnomes... it's caused by god damned gnomes...
This is exactly why a sailor would be warned by barometer alone of an approaching storm, and it is still a valuable warning tool. If the barometer drops abruptly, start getting the kids out of the pool, as a thunderstorm is likely soon to follow. There's no need for precision here, so an Aqara sensor will do fine. My barometer is mechanical, and was made in the 1930s - its an "heirloom"!
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