Not upset if it has more than temperature and humidity but I'm looking for accurate and reliable temperature and humidity sensors that are powered by mains power before I go off and make my own. I have a couple of the USB powered ones from another thread here and they are both wildly inaccurate and not consistently inaccurate so compensation isn't possible.
Thanks for the suggestions!
The Aeon MultiSensor 6 has an option for USB power and reports, among other things, both temperature and humidity. (The TriSensor is similar but doesn't do humidity, just temperature, light, and motion.) The "Environment Sensor" device by @iharyadi is also powered and reports these values (plus more), though I'm not sure if he has any available at the moment. If it matters to you, the former is Z-Wave and the latter is Zigbee.
I'm not sure what you're currently using and weren't happy with, so hopefully it's not either one of those. 
There may be more powered ones I'm not aware of, but I know there aren't nearly as many as battery-powered sensors.
Alternatively, as I'm sure you're aware and possibly going to try after this, a lot of battery-powered sensors are designed for about 3V power sources, and many people have found creative ways to modify both the devices and to "step down" readily availbe 5V USB power sources to work with these. Both this forum and the ST Community forum have several threads with DIY modifications like this that might give you more ideas if you haven't seen them already.
So far I've been through (battery driven) the SmartThings Button, Iris Motion Detectors, Visonic MCT-340 devices. They can be calibrated but it seems the biggest issue is the time it takes to respond to a change in temperature that's outside their programed range (e.g. .5C). Some of them can respond within 10 minutes and others take upwards of 30.
The graph below is a new SmartThings Button Sensor. While it tracks pretty fast, it appears to be responded after a 1 degree C change in my thermostat (approx 1.5 in F). The low is 69 and the high is 71. The green line is my thermostat and the orange line is the button.
I'm now tracking the Aeotec Multi-6 sensor with the USB plugged in and it's looking promising. The low at the start is 70 and the high is 71. I just started so it'll take some time to build a proper comparison. The green line is the thermostat and the orange is the Aeotec.
The Aeotec is a rather pricey little item, so if it works, I'll have to figure out some more automation to justify it being in 3 different rooms of my home.
Thank you for the suggestions.. Willing to spend to get the Aeotec Multi-6 if they hold accuracy once calibrated and are decently quick at reacting to change, drift is my enemy as my HVAC is based around the readings these things get. Suddenly one room reading 2-3 degrees colder/hotter throws a lot of things out of whack as the system tries to maintain 'comfort' in that room.
I have thought about just opening the zooz 4 in 1's have I have and hard wiring them, it's an option as they do work well enough for the most part. The Aeotec wall/ceiling mounts are tempting as well.
Are you grabbing data out of HE to plot these or using some other platform?
This is how I'm logging;
I was using WirelessTags which were pretty accurate, but I had to run that through ST and there was a 5-10 minute lag between. Then a few days ago, the software just started tanking and now I can't get them to calibrate for the life of me. I started the latest round of the temp adventure to finally get off of the ST hub (WirelessTags were the last thing holding me there).
In removing the delta between the rooms, the HVAC seems to run a bit more often (winter and summer) but not as long, and I'm not pushing air to the east side of the house during the summer that's needed on the west side. I also drive a house with them during the summer so keeping a reasonably accurate read on the bedrooms keeps that fan from running more often than needed.
You may want to research the Zoos some more. Will applying constant power increase the reporting period (as it does with Aeotec)? Another thing is related to what there accuracy is measured in. If it's accurate to 1 degree C, that's still somewhere between 1.5 to 1.8 F difference. It's these little things that are driving my ADD tendencies up a tree.
For the last few hours the Aeotec has been pretty spot on. It'll take a few more days to get a better collection of data, but I'm pretty impressed. I'll post a multi day graph once I get the data.
Thanks for the link, somehow missed that or forgot I read it, looks like another docker to spin up later! Will be interested to see if you like the Aeotecs after a few days.
As for the Zooz's, the sensitivity can be controlled a bit more than some:
So you can get it to respond somewhat quickly.
Aeotec TriSensor looks similar, but it only takes 1 battery and it can't be powered by USB...
Someone may have written a driver that will give you a bit more control on the monitoring portion. I'm using cSteele's Aeotec driver.
The Zooz 4-in-1 takes measurements about every 3 minutes and that interval can't be changed.
Zooz is supposedly coming out with a new usb powered 4 in 1 sensor. It was supposed to be released last summer and is still delayed. I check in at the smartest house every now and then to get an update, though been several months.
I have an Aeon MultiSensor 6 which has worked great using usb power and I happen to have just ordered 2 more.
but in hindsight I could have just cut an end off an old usb cord and wired 5 volts to my old xiaomi humidity/temp sensors.
Will they work with that input voltage or would you step it down? They all work off lithium coin cells which I think are maybe around 3.2V when new, but I don't know how tolerant they are of higher voltages. (Or if there's anything prettier than just soldering the wires to the battery compartment pins. I really need to read the threads I've mentioned but only kimmed😂)
Good to know, that's unfortunate.
I have done it on xiaomi motion sensors that use the same battery no problem.
I believe there are coin battery adapters on ebay or maybe amazon but they are more expensive and likely do not drop the voltage either.
I have also used usb adapters which give you a choice of voltage to 3.3 volts or 5 volts and wired them to battery powered sensors. Not as pretty but work well.
or
I have wired these to my door sensor
Door sensor
Here is a 24 hour graph and a 6 hour of my CT-100 thermostat and the Aeotec 6.
So far, it's looking pretty solid. The thermostat only reports in ½ degree increments. The Aeotec seems to swing between 2 tenths and 4 tenths of a degree around the thermostat. The temp range was 67F to 70.5F.
Looks promising, I ordered one to test with as well.
I did order a cheap 3v power supply and solder it to the Centralite 3325-S that I had laying around (with a dead battery no less) from my original ST bundle purchase. It shows 100% battery and seems to be displaying semi-accurate temperatures, despite the update timing being very slow obviously (10 minutes, the way it looks...)
Are you referring to this one?
Yes. Despite other's success I have never been able to get them to stay calibrated. They are constantly drifting Temp and Humidity wise.
Download the Hubitat app
