Very useful information! It would also be nice to know whether the offset changes over time depending on the 'activity' of the logger and/or on the actual ambient temperature.
I've done a further more precise check and
From 12:50:00 to 13:07:01 the Envoy/USB has been 26.3°C and the WiFiLogger mostly 26.6°C and twice 26.7°C so very close to each other this time.
I presume the Envoy/USB is being polled by VVP every few seconds and I can see the time and temp in Cumulus/Weatherlink.
The WiFiLogger realtime data screen updates every 5 seconds, except at the 5 min the realtime data screen does not update for about 2 minutes. At this 5 min upload interval WiFiLogger begins to FTP the 5 day logger data to my website (about 170,000 file size), and uploading WL, WU, PWS, CWOP, AWEKAS, WOW and one other. During this 2 min delay the indoor temp display does not change nor is there any change when the realtime data screen begins its new 5 sec updates so presume the indoor temp has not changed during that delay period.
Not sure why earlier there was about a 2°C difference and now nearly identical. Nothing has changed other than a couple of hours later.
I have been on this computer for the whole time doing other stuff.
I hope I have been clear enough.Paul