Davis Vantage Pro II Wind Direction stuck to North when connected to PC

[scotfiso]

Good Afternoon,

My name is Ago and I'm new to the forum!

Wanted to pick this forum's mind on an error I'm getting with our little Davis Vantage Pro II station at a little UK Airfield.

The VPII is connected to the PC via a USB Data logger in order to provide some data for a local Weather Information page. All information comes through correctly to the page except the wind direction. Whenever the station is connected to the PC via the USB cable, the wind direction is stuck at North with brief swings to the correct direction (when compared to the windsock).

This problem completely disappear when the USB cable is disconnected from the computer.

I have tried to provide a "cleaner" ground connection to the station with no real results. The manual refers to "Direction stuck at North" as  possible issue with the cable connecting the ISS to the station, however this doesn't explain why, when the USB cable is disconnected, the direction goes back to normal.

Any obvious things I'm missing or anyone that came across this before?

Thanks for your help in advance,

Cheers

Scotfiso

[xairbusdriver]

First, Welcome to the forums! The developer of WC is from the UK! Perhaps he can give you direct phone support!! In the mean time the real experts here are mostly west of me, so give them a few hours to offer some help.

Have you tried swapping the cable for a known good one? 🤔
If you can reach the anemometer, does it move freely?
Anywhere for a bird to rest/nest?! 😳

FLY SAFE!!

[JosBaz]

Peculiar problem... Can you confirm the correct wind direction is always shown on the console, independent of it being connected to the PC or not?
If it is, I would say the problem is not with the ISS, the ISS cabling or the console and I would focus on the PC and it's connection.

Has it worked without problems before, or is this since you installed it?
Are the WeatherCat gauges showing the correct direction, and is the problem limited to what ends up on the web site?

Good luck,

Jos

[mcrossley]

Sounds like a ground loop issue to me, especially as you have a cabled ISS. USB opto-isolators aren't cheap, so I'd try briefly unplugging the PSU from the console and let it run on batteries - does it work then with the USB connected? If it does, then try a different PSU for the console.

[scotfiso]

Thanks to all for the replies!

@xairbusdriver: Yep, swapped both the anemometer and the console cable for a good one still getting the same result!
@JosBaz: Yeap, I've got an old Weather Wizard III running alongside (contingency instrument) and the both that one and the windsock agrees with the VPII when it's not connected to the PC, and yeah totally agree it's not an ISS fault! Every parameter (aside of Wind direction) is looking fine on both Weathercat (only use it for testing on my laptop really) and Weatherlink.
@mcrossley: Yeap, a ground loop is definitely possible due to the wiring of the whole place really! I've tried running it on battery but the issue is still there. I've got a USB Opto-Isolator on order (only a cheap Amazon one though so probably not best quality), see what happens!

Also thanks for the warm welcome!

Cheers

Ago

[Fifth Horseman]

As I understand it the cabling of the wired VP2 should not be earthed so an earth loop should not be the cause of your problem. The data from the lSS is in the form of serial data so if wind direction data is being lost then it must be a problem at the lSS end. It is possible that plugging the USB logger into the computer is affecting the supply voltage to the ISS which in turn affects the wind direction reading.

Have you tried using a different computer (laptop perhaps) or a USB hub to see if the problem still occurs? If it does then there may be an issue with the USB logger or the console itself.

Personally l would rather use an IP based logger like the meteo-pi available from https://shop.weatherstations.co.uk/meteo-pi-ethernet-2087-p.asp

[scotfiso]

Morning All,

So, had a little try at the cheap USB Opto-Isolator I managed to get on Amazon and that seem to have solved the issue!
We'll be testing it as part of a whole system for the next 14 days and we'll see if that has actually solved the problem for good!

@Fifth Horseman: Initially that's what I though, and I've tried the VPII with another computer in the VCR which gave the same issue. Admittingly, I haven't tried a laptop or anything detached from the building "Mains" supply which are far from clean so to be fair that might be the source of the noise which in turn is affecting the VPII Power supply and the whole station.

Thanks to everyone for the help and I'll keep you updated!

Cheers

Ago

[mcrossley]

Good news. There is an "earth" through the USB of course, but that is probably floating like the VP PSU. I have seen considerable voltage differences between devices on double insulated PSUs in the past - sufficient to cause a small visible spark when connecting them! Needless to say I had issues with those two devices (TV and DTV recorder)

[Blicj11]

One of the comments I found from those who had tried the least expensive USB Opto-Isolator on Amazon: "I had been having a problem with the program disconnecting randomly due to static or electrical interference. Installing this solved the problem completely." This leads me to agree with Mark. Hope this solution turns out to be all you need. Thanks for keeping us in the loop (ground isolated, of course.)