Davis Vantage Pro 2 - Setting Wind Speed to Tenths

[Ryan818]

I just got a new Davis Vantage Pro 2 and am trying to set the wind speed on the console to display in tenths instead of rounding the wind speeds. Does anybody know how to do this. I have looked in the manual and had no luck finding a way to do this. Any help would be much appreciated.

Thanks,
Ryan

[nikoshepherd]

That’s a very good question, I suggest you email Davis. My VP1 manual shows tenths on the screen pics but I have never found how to make it do that.

[Ryan818]

Thanks nikoshepherd,

I guess I will have to email Davis. I found it intersting that they show the wind speed out to a tenth in the manual, but no instructions on how to set it that way. Maybe someone else on the forum has figured it out. I appreciate your help.

Ryan

[administrator]

Can you change the units on the console display? Perhaps they’re showing m/s and therefore need the tenths to avoid having the increments too large. Also wind speed In m/s is unlikely to get to more than two digits, so they can use the third digit as tenths, where in mph (and more likely in kph) you may need all three digits.

[Ryan818]

I am displaying my wind in mph. When I change to m/s I get the wind in 1/10’s.The Davis manual shows a picture of wind speed in mph with 1/10’s (for instance 5.3mph is displayed as 5.0 mph on my console. My old WS2310 displayed wind in 1/10’s. I was just curious as to whether there is a setting in the console for adjusting to 1/10’s. Maybe there is or isn’t. Thanks for the insight on this little setup issue.

Thanks,
Ryan

[prodata]

@Ryan818 post:5

The Davis manual shows a picture of wind speed in mph with 1/10’s (for instance 5.3mph is displayed as 5.0 mph on my console.

I suspect that’s almost certainly the equivalent of a typo when the illustration for the manual was prepared. AIUI the anemometer can’t physically measure anything other than integer mph. I may be wrong. but I have a recollection, maybe based on the wind calibration number but I haven’t got the WMII (which has essentially the same anemometer) manual to hand in order to check, that one revolution of the cups (ie one switch closure) per 2.5 sec measuring window equates to 1mph, but even if this figure isn’t exactly right I think the general principle is. You can’t have half a switch closure - either it happens or it doesn’t - and so your basic measurement is an integer one. Certainly the VP2 specification quotes the wind speed resolution as 1mph which ties in with what the display actually shows. And in fact the accuracy spec is the greater of 2mph or

[Ryan818]

Thanks for the great reply prodata. I think you are right on as it being a typo in the manual. I sent in an email to Davis anyway just see what they say. I guess I was so used to seeing 1/10’s of a mph in my old WS2310 console. If this is how the Vantage Pro is set up I don’t have any problems with it. I figured I would see if there was any way around displaying an integer value in the wind field.

Thanks,
Ryan

[nikoshepherd]

I tend to agree with the typo theory, but you would think they would have answered the question often enough since the original VP was introduced to have fixed it in the VP2 manual :?

[prodata]

[quote author=nikoshepherd link=topic=7456.msg50355#msg50355 date=1107047133]
I tend to agree with the typo theory, but you would think they would have answered the question often enough since the original VP was introduced to have fixed it in the VP2 manual

[Ryan818]

@prodata post:9

The only excuse I can think of (besides inertia, oversight, the fact that Davis is actually a relatively small company with everyone in development/support fairly busy etc) is that it might have been left in case the type of anemometer was ever changed. It has been suggested from time to time that, for example, a set of wind cups with more than one magnet could provide increased wind speed precision at low wind speeds. And this could open the door to meaningful resolution of <1mph (though accuracy would still presumably be a stumbling block). Or maybe the type of anemometer could be changed altogether - a photoelectric one might be able to provide several pulses per revolution of the cups for example. Certainly there are aspects of the VP design that are not currently publicised that provide the capability for future additions, eg the six slots in the structure of the Weatherlink archive database structure ‘reserved for future sensors’. Of course whether they ever will be used is another matter altogether - maybe Davis are just giving themselves the options just in case they ever need them.

I am curious as to why Lacrosse Technologies for instance has the ability to track wind speeds in 1/10th’s of a mph. This is the main reason I stumbled upon the MPH question, given the read out on my old WS2310 console. I am sure other companies have been able to introduce 1/10th’s precision into their consoles. The primary difference between the WS2310 and Davis VP anemometer is the use of cups vs. the turbine construction on the 2310 model. Do you suppose this accounts for the accuracy differences? I guess we have something to look forward to in the future if Davis decides to implement some of the additional sensors. Oh well, I am happy with my Davis VP so far, I was just puzzled by how they were displaying wind readouts on the console. On a side note I am also stumped as to how to set the special alarms on the console. The instructions in the manual are not very thourough. If anybody knows how to set the alarms please let me know.

Thanks,
Ryan

[prodata]

@Ryan818 post:10

I am curious as to why Lacrosse Technologies for instance has the ability to track wind speeds in 1/10th’s of a mph.

I don’t know. It may be that they have a more sensitive impellor mechanism. If for example this turns more than once for every mph then it may start to get the potential to read meaningful fractions of an mph unit. The main downside might be that at high wind speeds the impellor can’t keep up and starts to under-read. The Davis unit is specified to read from 2-150mph with an accuracy of

[windy2]

hi
yes, the little fan type anenometer has a very high RPM , and so yes they can get DP for windspeed…that will be the reason
(it screams at 85 knots (using a compressor!)

[Ryan818]

@windy post:12

hi
yes, the little fan type anenometer has a very high RPM , and so yes they can get DP for windspeed…that will be the reason
(it screams at 85 knots (using a compressor!)

Thanks Windy,
I guess that answers the question. If I get any different response from the email I sent to Davis I will make sure to post it here. I figured I would pose the question to the weather station experts on this forum first.

Ryan

[windy2]

the bottom line, is that if a anenometer only has an accuracy of say +/3 mph, then showing 0.1 mph resolution is a bit pointless…
and wind changes quickly, and so you are not going to see it go through 0.1mph within a whole mph anyway, if you get my drift

[nikoshepherd]

@prodata post:11

But conceivably it’s not more sensitive than the VP anemometer and LaCrosse are simply trying to trap the unwary purchaser by implying that the precision (ie reproducibility of values) is better than it really is. Showing an extra decimal place on the display for any parameter eg wind speed, temperature, or whatever is pointless if the resolution isn’t accompanied by comparable precision, and preferably accuracy too. Personally, I’d opt for the more professional, scientific and honest approach of only displaying data to a resolution that was justified by the quality (ie precision and accuracy) of the data. If this means using just integer values then so be it.

I think you and Brian are right, even if you look at the high end stations, Texas, Campbell etc they don’t claim better than 1 mph. 0.1 looks good but it’s meaningless.

[Ryan818]

Just for everyones information this is the response I got back from Davis regarding this issue:

"Hello,

The wind speed on the Vantage Pro and Vantage Pro 2 only can be shown as whole numbers for MPH. The manual incorrectly shows it in 10th’s.
Tom Raymond
Davis Instruments
Technical Support
510-732-7814
[email protected]"

I guess at least they admit to the manual being wrong. Thank you everyone for putting this into perspective. I now realize that showing wind speeds in 1/10’s does not improve the accuracy of the values.

Ryan

[nikoshepherd]

Prodata was too modest to mention it but his site has a nice FAQ for the VP that you may find useful as a new user http://www.weatherstations.co.uk/vp_faqt.stm

[Enzo]

Hello,

I ve had this problem bug me too. After a loooong search it is apparently a design fault/feature of the VP2…!

What happens is that the VP2 and the associated data logger only have an accuracy of ±1mph and actually store this value as an integer, therefore there is no way to improve on this value nor to display decimal mph.

When you do see decimals in the m/s display it is simply the conversion from integer mph to m/s. Again the steps in the display can get no better than 0.45 m/s. Thats just the way they built the damn thing.

Yannis from Athens