I've had the Van-O-Meter development board sitting around and finally put it to use the other day. We've been getting some cold nights lately and I wanted to see what the temperature was getting down to in the van. I don't have an exterior sensor so I compared the van interior temperature with the local airport temperature data. I can see the airport from camp, it's only a couple miles away so it should be pretty close to the actual outside temperature.
It's clear from the data that the van temperature sensor reading is offset by approximately 6 degrees from the airport sensor outside temperature. The development board temperature sensor is factory calibrated. So either the board is putting off some heat, the van interior stays warmer than outside, or there is a significant temperature differential between my location and the airport. Not really sure which it is yet, need to do some more experimenting. The airport sensor got down to 36 and the van sensor got down to 43. That's sleeping bag hibernating temperature for me.