Davis Weather Envoy reporting external temperture 4˚ F higher than actual.

[elagache]

Dear WeatherCat Davis fans,

I had a very strange problem with my Davis Vantage Pro-2 setup this morning.  When I got up I noticed that the external temperature reported by WeatherCat was about 4˚ F higher than what was displayed on the VP-2 console that is in another room.  I restarted WeatherCat and rebooted the Mac - no effect.

Finally, I power-cycled the Weather Envoy and only then did it start reporting the same external temperature as the console.

I took a careful look at the WeatherCat data files and found that at 4:19 am the exterior temperature jumped from 14.8˚ C to 19.8˚ C.  At 7:52, the data shows a drop from 19.9˚ C to 16.4˚ C.  So unfortunately, my data is definitely tainted.  What is extremely strange in this is some sort of hardware problem is why anything is reported at all.  Hardware doesn't "invent" data.

I posted my question on the WXForum and have already gotten one reply:

http://www.wxforum.net/index.php?topic=24010.msg230480#msg230480

Mark (MCrossley) suggested that somehow my Envoy was receiving data from some other local Davis VP-2.  That at least would explain why there was any data, but I'm not aware of anyone else in the area having a station and the Davis range is only about 300 feet, it would have to be a neighbor who has just put up a station.

Beyond that I"m utterly baffled.  We are a small community, but if anybody has some thoughts on this one, please do tell!!

Cheers, Edouard 

[elagache]

Dear WeatherCat Davis owners,

Well the folks on WXForum came up with about the only plausible explanation: indeed there must be another Davis station somewhere nearby and my Weather Envoy started picking up that station instead of my ISS.  Here is the thread again for the curious:

http://www.wxforum.net/index.php?topic=24010.msg230480#msg230480

It is rare but does happen as noted by the WXforum members.  They recommend changing the station frequency by shifting the transmitter ID to solve the problem.  It is a bit more involved for me than most because I need to change the ID on the ISS and the Wireless Temperature/Humidity Station and then adjust the Console and Weather Envoy to reflect those changes.  Since we are in the middle of an autumn heat wave, I'll wait for a bit of cooler weather to make the switch.

Once I've gone through this, I'll go ahead and document it on the WeatherCat Wiki.  Anyone setting up a new Davis station in an urban area might as well switch the transmitter ID as part of the setup process.  Given that anyone else who might install another Davis station in your neighborhood is very unlikely to do this sort of extra work, that should be enough to make sure your station isn't bothered by . . . . overcrowding!! 

Time for me to move to da' real countryside!! 

Cheers, Edouard