2. Extended experimentation shows that plugging the data logger into the console by itself does not cause the issue. ..... It
is only when the data logger is connected to an active (powered) USB port on a computer/router.
Obviously, the USB logger contains active circuitry (more than the serial logger), to convert serial to USB. That circuitry dissipates power, of course, which means heat. And the harder the logger (including the USB converter) works, the more heat. You have rather conclusively demonstrated the possible extent of that effect. But (at least from my tests), the effect does not occur just from connecting the logger to the computer.
My system here uses a serial logger, and WeatherLink software, normally running at a download interval of 10 minutes. I have an essentially-duplicate test system, so I made some tests. I can't detect any heating effect (difference) between:
1. Logger disconnected from the computer.
2. Logger connected to the computer, but WeatherLink not running.
3. Logger connected to the computer, with WeatherLink running at 10-minute download interval.
I would not expect to be able to see a difference with a USB logger, either. But perhaps you would run that test.
However, you are quite correct - I can observe a slight (perhaps 1/2 degree) heating effect when I run the WeatherLink Bulletin for 30 minutes or so. I would expect that effect to be somewhat greater with a USB logger.
I eliminated Meteobridge as the culprit by reproducing the results with WeatherLink. Here's what I know so far:
2. Extended experimentation shows that plugging the data logger into the console by itself does not cause the issue. It is only
once the logger is being read often as Meteobridge-like devices would, or with Weather Bulletin running on WeatherLink. ....It
is only when the data logger is connected to an active (powered) USB port on a computer/router.
Note strikethrough" replaced by italics above.
Many users will never notice this effect - because they don't read the data that frequently (Meteobridge et al) or run the Bulletin continually. [Or, I suspect - uploading to WeatherUnderground in "rapid fire" mode].
Having said that, Davis should properly be interested in the information.
When you talked with Davis technical support, did they perhaps think that you were saying "Your USB logger heats up the console all the time", rather than "Your USB logger heats up the console if you're running the WeatherLink Bulletin or using it very rapidly"?
[And it seems clear that in your earlier tests, MeteoBridge did significantly affect the results - in the same way that the Bulletin does when using WeatherLink.]