Topic: I am testing Davis vs. RM Young Wind Head to Head (Cups to Propeller)

[twcmaster]

Yeah, I get that sometimes when using Chrome. You would think Nest and Chrome would play well together.

Try a different browser. As much as I despise it, IE11 works great.

[twcmaster]

Of course if gust is what you care about, and consider the higher to be the better

The VP2 anny is what, 6" above the RMY? No way the error he's reporting would be that great unless one or both are inaccurate, within specs.

Yeah, when the Young tail swings around it clears the top of the Davis direction vane by millimeters, so they are pretty close in height.

Ultimately, down the road I am looking at buying a brand new Young HD with ceramic bearings to put on the roof. The Young I currently have (while in great condition) is used from Ebay. I did test with the Wind Monitor Junior though with similar results and that was brand new. The testing I did with that was with the Davis Anemometer transmitter though not the wind tracker display, so that adds some complexity in making a comparison.

[DaleReid]

I'm an anemometer junkie, started with tinkertoys and a few ping pong balls carefully sliced in half when I was 5.

I have a couple of Met One 34Bs right outside my window, exactly the same height on a level commercial mounting bar, and just far enough apart to not have their tales hit one another.  Prevailing winds are 90 degrees to bar, so no downwind turbulence effect that I can see and most of the time they are not shadowing one another.

I've noticed many times, in light breezes, that one is slowly turning and the other not.  then as if in slow motion the other starts while the first spind down.  The direction vanes only match during stronger winds and even then there is oscillation.

To carry it further I have two Youngs 05103s and a Davis and a Peet along with a Texas Weather sensor all as close to one another as I can get and yet be funcctional.

One of the Young's propeller is turning when the other brands are still in light winds.  In high or at least higher winds there is a delay in the Young turning into the wind, while with very gusty winds I can see the cup types spin up noticeably.  something I always thought was that gusts were longer (as in time and distance the wind travels) than they sometimes seem to be much shorter in duration than I'd observe, with some being in tenths of seconds, not sustained.  Remember that the counters that time rotation are different, and that the Young puts out three 'pulses' or oscillations per revolution of the prop, and for the cup types many of the Campbell Scientific and other data loggers will sense for a full second before calculating the speed.

There are so many factors that I believe it is naive to think that one is vastly more important than the others.  The only true test might be a close placement in a stable speed wind tunnel with a heated wire anemometer or ultrasonic to determine the accuracy in sustained wind.

I think there was some discussion a few years ago about gust accuracy.  I wonder if there is some Master's degree paper written about gust response.  And I'd also be interested if cup types can over read a gust due to acceleration of the mass of the cups to actually speed beyond the wind until resistance on the 'back side' would bring it back down again.

Thinking of this, I'm betting that the very brief character of gusty wind (tenths of second variations vs. sustained as one might think) would be the greatest error.  An interesting experiment would be a second by second graph of the output of a data logger overlaid with an ultrasonic which theoretically could be sampled many times per second and the most accurate, massless, sensor of wind speed.

[miraculon]

I also have a setup with the Davis and an RM Young Wind Monitor (Jr). I have data showing the two in charts. I frequently see the same results, the Young is far more responsive to very light winds, and the Davis peak gusts will be higher. Some time ago, I looked into this, and there are papers written about "anemometer cup overspeed". You can enter "anemometer cup overspeed" into Google and find several papers (most require purchase). Here is a PDF of one that is available: http://www.windsensor.com/application/files/8814/2694/4640/The_Working_of_the_Cup_Anemometer_20140619.pdf

Here is a link to my wind page which shows both the Young and Davis in operation. (I also have a plot for the local marina about 2,000 ft away, so ignore that in the plot).

http://rogerscityweather.com/wxDavisYoung.php

The Young is my default for most uploads, but I do have the VP2 data uploaded to APRS. See KE8DAF-13.

Here is my installation of the two anemometers (the wind was calm when this picture was taken, hence the random directions):



Greg H.

[DaleReid]

As Greg mentions there are several on line detailed research papers discussing 'overspeed'(apparently there are factors which cause a cup anemometer to speed up faster than it slows down, go figure) and the number of cups, the diameter of the cup, the distance from the rotational center along with hemispherical vs. conical and three vs. 4 cup design.  Enough to make your head spin like, well, an anemometer on a blustery day.

The papers which dealt with the comparison of propeller (usually Young) vs. cup all stated the noticeable lower reports all due to the orientation time and missing measuring the column of air passing by.

All in all it makes little difference, and if you are reporting gusts, then the cups are better.  For average wind speeds either is fine.  I participate in a large television station reporting network over most of Minnesota and some of western Wisconsin, and the wind speed is supposed to be submitted as the average wind speed.

[ocala]

Of course if gust is what you care about, and consider the higher to be the better

The VP2 anny is what, 6" above the RMY? No way the error he's reporting would be that great unless one or both are inaccurate, within specs.

That's what we do here. We split hairs, then split them again.
Gotta have accurate data man!

[blizzardof78]

Regrettably I'm still not able to see the video display. When I tried it on IE as suggested, I was able to view for a second, then it went blank. Oh well, any other suggestions???

[CW2274]

Of course if gust is what you care about, and consider the higher to be the better

The VP2 anny is what, 6" above the RMY? No way the error he's reporting would be that great unless one or both are inaccurate, within specs.

That's what we do here. We split hairs, then split them again.
Gotta have accurate data man!

Me saying "preaching to the choir" would be an understatement.

[Mattk]

.... RM Young model would do a better job at catching wind gusts as it updates every second vs. 2.5 seconds for the Davis

Being an RM Young then are you running this through a Davis Universal Anemometer Interface (6336), I have not seen an update spec for the 6336 so even if the RM can update at 1 sec are you sure of the update interval thru the 6336 or thru the ISS?

Also what wind cup option have you selected?

[twcmaster]

.... RM Young model would do a better job at catching wind gusts as it updates every second vs. 2.5 seconds for the Davis

Being an RM Young then are you running this through a Davis Universal Anemometer Interface (6336), I have not seen an update spec for the 6336 so even if the RM can update at 1 sec are you sure of the update interval thru the 6336 or thru the ISS?

Also what wind cup option have you selected?

I am using a brand new from the factory RM Young Wind Tracker 06201 and the 6410 Davis anemometer that I am comparing it to has the wind cups set to large on a Vue console. I have also used a Davis Universal Anemometer Interface (6336) with similar results, but with a Wind Monitor Jr and the cup size set to other on a Vue console.

[Scalphunter]

After an life at sea I have seen the RM young units take an beating that would  wie out most WX sensors.  Only time I even had to replace an unit was in the military after  couple units got blown away.  Hurricanes tend to do that  with  the wave acton. Davis  may be good except for the temperature reading not going low enough but if you want to put up an unit that might need looking to about every  10 years the Young the way to go. They take and licking and keep on working.

John

[twcmaster]

Hi Everyone!

I wanted to provide an update to this thread in case anyone had any interest in Davis vs. RM Young.

My Davis 6410 crapped out again after about a year of service. This one is completely seized up on the top (direction) and bottom (speed). This is the worst one yet and also the one I have had the least amount of time. To be fair it does take quite a beating. I've lost track of how many I have had to replace, so I went out and bought a brand new RM Young 05106 Marine Model (the new version with ceramic bearings) and a brand new Davis 6410. I have been testing them at "ground" level (which is still 100+ feet above the water) mounted on the same post only mm apart from another for the past couple months.

My last 05106 was bought used off eBay and was the older model, so I was hoping a brand new one might change things plus I like the idea of ceramic vs. stainless bearings. I am having the same "issue" where the wind speeds somewhat match at lower speeds, but when the winds increase they are off quite a bit, and gusts are even worse.

Anyway, the roofer was here today to replace a bunch of missing shingles from the last storm, and I had him put both units way up on the roof since we just happen to have a storm rolling through here tomorrow.

I know everyone has their own opinion on cup anemometers and aerovanes, but what frustrates me the most is regardless of which device is technically more accurate, the 6410 is not reliable enough to keep having to pay someone to go on the roof to replace it each year....and even if the Young is perfectly accurate being the more expensive model, all my wind records from all the storms over the years now mean squat as I will never be able to compare apples to oranges.

I have more to add to this thread later as I also set up some other stations to compare to these two and that made me scratch my head even more, but more on that later.

I just set up a new Nest camera to see both the Young and Davis consoles side by side so I just wanted to share before the big winds came in if anyone was interested in watching.

I'm open to comments, feedback, and criticism if anyone has any! 

https://video.nest.com/live/bxHi99uZFx

P.S. The wind direction is not calibrated on either console yet (just worried about speed right now).

[DaleReid]

The camera is a neat idea and I'll peek in once in awhile to see how they are doing.

I'm thinking about your comments that all your old archived data won't be worth much if you switch to having the Young be the supplier of wind speed.

I would gently suggest you are wrong, and that wind speeds are, at best, a percentage thing.  7 mph vs. 5 is really no big deal, but maybe you see or expect something I don't from those data.

And consider that the RM Youngs are used for research purposes, anywhere from monitoring around the Cape Canaveral and other places, to many official stations to true university projects research.

If you are looking for the max possible gust without over rev-ing, then cups may be a bit more hitting on the absolute of the air parcel in the small area, but might be off 5 or more mph just a few meters away.  So how do you know you have your sensor located where the max will be?  You don't. 

I, myself, wouldn't loose a lot of sleep over the old data.  It's going to be very close.  I think that the availability of sensors makes us worry that we have the right one.  I have a friend with 5 or 6 raingauges and he nearly drove himself crazy trying to calibrate the tipping buckets all one summer.

Recall the adage:  A man with one watch will know what time it is; he who has two will never know for sure.

I had an Accutron watch back when they were the cat's meow, and so many factors like temperature of the environment, how active the wearer was and what position the watch was in for long periods made knowing what time it really was very hard to determine.  Quartz blew them all away. 

Just enjoy the ride, you have some nice looking stuff there. 

[Mattk]

Lots of things have changed since this thread was started, key one being the Davis anemometer interface is no longer available and without that makes the Young rather difficult to connect. This type of situation is ideal for some of the new Ultrasonic anemometers that will work with Davis without any additional hardware or interfaces

[miraculon]

I did decide to get a spare 6336 (UAI) in light of the fact that it was discontinued by Davis. I must have gotten one of the last from SI, and they are now out of them.

It will probably sit in the box for a long time, but I figured that Anemometer transmitters are a dime-a-dozen so to speak and readily available. (also all SIM transmitters are the same, I am using what was originally a Temp Station transmitter as an anemometer transmitter.)

I also figured that RM Young wind sets are commonly available on the used market, or if I had to I'd just get a new one if some kind of destructive event occurred and I had to start over.

Sometimes I see a direction skew between the two vanes. I am referring to the actual vanes and not just the indication  by the consoles, etc. This seems to happen at lower wind speeds, if it is a strong steady breeze they will physically match direction. It is possible that this is caused by my mounting scheme with the cross-bar.

Greg H.

[JCA433]

I replaced my Davis anemometer earlier this spring because the wind cups would not turn in light winds caused by bad bearings. It lasted about 2.5 years.   I discovered this problem in the spring when I saw the wind cups not spinning even in modest wind speeds.  The anemometer was dismounted and brought  indoors and when I rotated the wind cups by hand there was resistance to the cup rotation.  Davis should use corrosion resistant bearings because in my location the humidity is often very high and with that so is the risk of corrosion.