OK. It took a long time to get to it, but Davis has been a real help so far. First they sent me a new 6510USB. When that didn't clear up the issue, they sent a new console. That doesn't clear the issue either. Two consoles and two data loggers with the same issue. I eliminated Meteobridge as the culprit by reproducing the results with WeatherLink. Here's what I know so far:
1. Reading data from Connecting a 6510USB on a Vantage Pro 2 console to an active USB port on a computer/router
affects the indoor temperature readings by a degree or two, usually in the upward direction.
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.
Both consoles have 3.12, and the same day I first received the data logger I upgraded from 3.0 to 3.12 so there was never a time I tested a 3.0 firmware with this issue. I don't know if the hardware is any different, but both are "green dot" consoles.
Can anybody with a green dot console and 3.12 firmware reproduce this? If you want to follow my steps:
1. Have another thermometer handy for reference. Take note of how it reads compared to the console
over a period of time and note the offset (if any). It's important that both the console and the thermometer
are as close as practical.
2. If your data logger is being read through a 6510USB on a frequent and regular basis connected to an active USB port,
disconnect the cable; if your console isn't being read on a frequent and regular basis if your data logger is not connected
to an active USB port, connect it now.
3. Wait at least 30 minutes and compare the temperature to the reading from Step 1, and also to the reference
thermometer. If you are experiencing the issue, your indoor temperature will have changed by anywhere from
0.8 to 2.0°F (usually higher when connected to an active USB port). If you watch the console for an extended
period (days), you may notice that the error value drifts slowly between 0 and 2°F.