Thank you sir!
I just want to share some of my note when I started making my own Zigbee Environment sensor.
In regard to temperature, a lot of battery powered implementation can provide ambient temperature reading by using MCU internal temperature sensor. In battery powered sensors, most of the time, the MCU will be sleeping most of the time. Therefore, its internal temperature sensor reading will be close to the room ambient temperature where the sensor is placed.
The same MCU, when it is powered all the time, will be affected by "self heating". Unfortunately, this effect will be difficult to be calibrated if it were used to read ambient temperature. The offset will be dynamic depending on how busy the MCU is.
For some cases, where one need to read room temperature, the battery powered sensor is a "win-win" solution. Without additional cost the vendors can provide room temperature information. However, these devices will be limited by power consumption and side effect to avoid self heating.
If (or when) one have a need to stress out the reading on these devices either by configuring more frequent report or attribute queries, you may push to the limit of the device power limit as well as the open up the side effect of "self heating".
In Zigbee, the reporting capability of a sensor should be configurable up to a second resolution. However, I suggest that one want to be careful in a way that you do not want to be too aggressive so that you stress out the MCU.
Xiaomi temperature, humidity and pressure sensor is one of devices that has its own dedicated sensor for temperature reading. In this case, the design of the board and casing has much more influence on the temperature reading. It still uses battery. Therefore, it is still limited on the power consumption in the context of reading interval.
As a user/buyer, I hope that I can add to our knowledge base so that we can make a better buying decision.
Well, I gave the SmartThings Button my best, but I have to return them. They are very difficult to calibrate, have a very long time (in minutes) before updating their temp and run anywhere from .8 to 1.2 degrees in difference from the current temperature (e.g. if my thermostat says 72, then a button could say 71.2 to 73.2 and that's with a lot of calibrating). In @muir graph above, which is showing 8 hour increments, there is a 3 degree delta at times. They are probably good for someone who wants a very general view of a temp, but I wouldn't recommend them for driving HVAC or whole house fans (my use cases).
I've had to go back to the WirelessTags. They are pretty cheap at $29 per 13bit version tag (plus a onetime $29 for the base station). They are accurate to .4F and you can set the update timer on them (2 minutes to 4 hours). Unfortunately I can only link them into HE via my ST hub and hub linker. This can add at least a 4 minute delay to reflect in HE. I believe someone has expressed interest in migrating the driver, but I'm sure it'll be a while.
I hope this helps.
Here's my post in another thread about the WirelessTags.
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