Author Topic: WMR 968 anemometer (Read 9393 times)

blemire · « **on:** October 22, 2008, 01:20:50 PM »

Hello all.........I hope someone can help me here. I've repositioned, reinstalled and checked the position of my anemometer but notice that it still seems to record the wind speed incorrectly. When the trees are bent over and the cups are spinning wildly, I have a hard time agreeing that the highest gust is 8 mph!

Is there a way to calibrate the main unit or something??

A wx rookie in New Hampshire

sam2004gp · « **Reply #1 on:** October 22, 2008, 02:58:42 PM »

The only way to calibrate it, as far as I have seen...

Is to have a couple of other different brand of anemometers at your location, then you average them out. But that is not easy or cost effective to do.

Also there was once a thread at the old Ambient forum that stated that the WMR968's were notorously low in recording their speed. So in VWS, in calibration settings, change your gain from 1.00 to 1.25. So when you record 5.00 MPH on the console for example, VWS should read 6.25. 2nd example when you read 40MPH on the console, you get 50MPH in VWS. I did this and noticed that my average wind speeds seem to be more inline with the stations around me, per WU.

^^^^So this is what I am sticking with until someone can give a better answer. And if anyone has one, please respond here, and help us all out.

Anthony · « **Reply #2 on:** October 23, 2008, 08:52:28 AM »

I have also gone back to using a gain of 1.25 for both speen & gust. Since doing so. I have not revieved any QC reports from CWOP. So this indicates to me. That my wind readings are a little more in check.

W Thomas · « **Reply #3 on:** October 23, 2008, 10:56:57 PM »

Same gain setting I am using here. Still seems a little low but I do have a lot more trees than I need
that tend to block the flow of wind in the area of the anemometer. And it is in the best place I have available.

It's been rather windy here today so it might be a good time to experiment

Wayne
www.smythweather.net
CW8217

JOE · « **Reply #4 on:** October 24, 2008, 11:02:22 AM »

Don't know anything about WMR, but is there an adjustment for cup size?

sam2004gp · « **Reply #5 on:** October 24, 2008, 11:08:38 AM »

Nope, just gain and offset. But I can think of no reason to use offset for any adjustment on the Anemometer.

igor · « **Reply #6 on:** October 25, 2008, 04:13:46 AM »

do a car calibration test
on a quet day drive 20mps and stick it out of the window, it should also read 20mph

sam2004gp · « **Reply #7 on:** October 25, 2008, 07:40:33 AM »

Quote from: igor on October 25, 2008, 04:13:46 AM

do a car calibration test
on a quet day drive 20mps and stick it out of the window, it should also read 20mph

Wow, 20 Miles Per Second. If I had car that could do that speed, I could afford a much better weather station than the WMR-968.

JK,

Now however, this is a good idea. But you have to unmount everything and take your station with you. I have thought about doing this myself, but it is not feasible at this time.

SLOweather · « **Reply #8 on:** October 25, 2008, 09:52:27 AM »

2 suggestions if you do this...

First, calibrate the car by timing while driving at a set speed between 2 or more mileposts on the highway, and calculating your speed. From http://en.wikipedia.org/wiki/Speedometer:

"Speedometers are not totally accurate, and most speedometers have tolerances of some 10% plus or minus due to wear on tires as it occurs. Modern speedometers are said to be accurate within 10% but as this is legislated accuracy, this may not be entirely correct. This can make it difficult to accurately stay on the speed limits imposed; most countries allow for this known variance when using RADAR to measure speed, although levels of some 3 km/h or 3% are also used in areas of tough enforcement."

So, if your speed says 20 mph, you might be going as little at 18 or as much as 22 mpg.

Second, make sure the anemometer is held or mounted far enough away from the car that it's out of any slipstream that will make the speed appear greater. (Slipstream's not the right word, but you get the idea. It's too early for my brain to be fully warmed up.

)

mackbig · « **Reply #9 on:** October 28, 2008, 05:40:04 PM »

Mine has always seemed a little on the low side. I applied the 1.25 gain on the weekend. The past few days it has been pretty windy. I am tracking really close the EC site just up wind from me. Today 35k winds (with mid 50's gusts)

Andrew

Impala88 · « **Reply #10 on:** October 29, 2008, 06:45:05 AM »

I wish VWS had a variable gain for the wind speed depending on wind direction. I have trees on the north and east which block the wind. It would be nice to have the gain to automatically increase for a wind direction of 0º to 100º then revert to the "normal" setting for wind directions of 101º to 359º. Is something like this even possible?

Anthony · « **Reply #11 on:** October 29, 2008, 07:46:18 AM »

There are weather programs that have this feature. Weather Display is one of them.

mackbig · « **Reply #12 on:** October 23, 2009, 10:21:44 PM »

I proved today that the 1.25 gain for wind and gust for the old os anemometer was a pretty good measure. Nice job Sam, served me well the past year.

VWS - os wmr 968
Today's High Wind: 50.4 km/hr (4:51pm)

WD - vp2+
Today: 50.0 km/h 4:51pm

Andrew

Anthony · « **Reply #13 on:** October 24, 2009, 07:30:24 AM »

But that's only if the OS anemometer hapens to measure it.

sam2004gp · « **Reply #14 on:** October 24, 2009, 08:00:11 AM »

Quote from: Anthony on October 24, 2009, 07:30:24 AM

But that's only if the OS anemometer hapens to measure it.

This is true.

Boy that guy with the "big time" gear now, is rubbing it in.

mackbig · « **Reply #15 on:** October 24, 2009, 08:05:11 AM »

Hey now, I was just going to post how impressed I was that all my os measures are pretty close to the vp2... with that offset of course. Even the 4 year old rain gauge is keeping pace (when it tips). Maybe I dont need this new toy...

nah, I'll keep it a bit longer. 4 days is not statistically significant.

Andrew

Quote from: sam2004gp on October 24, 2009, 08:00:11 AM

Quote from: Anthony on October 24, 2009, 07:30:24 AM
But that's only if the OS anemometer hapens to measure it.

This is true.

Boy that guy with the "big time" gear now, is rubbing it in.

sam2004gp · « **Reply #16 on:** October 24, 2009, 08:08:19 AM »

Well, I think you should donate it to a non-profit org. like mountcrawfordweather.org

DanS · « **Reply #17 on:** October 24, 2009, 08:20:17 AM »

Quote from: sam2004gp on October 24, 2009, 08:08:19 AM

Well, I think you should donate it to a non-profit org. like mountcrawfordweather.org

whoa there! non-profit org.?? I don't have a "Please Donate" button on my web page so I think it only fair any unused/unwanted PWS equipment would be better donated to a truly non-profit org. like ThaiWx.

$\:D/$

sam2004gp · « **Reply #18 on:** October 24, 2009, 08:21:50 AM »

Hey Dan, stop cutting in on my piece of the action.

JK

DanS · « **Reply #19 on:** October 24, 2009, 08:26:42 AM »

Just how many os anemometers do you have now, anyway? Must be a few. The way you go through them maybe you do need mackbig's more than I do.

sam2004gp · « **Reply #20 on:** October 24, 2009, 08:30:51 AM »

For your info I have 2. One broke and one working.

Bashy · « **Reply #21 on:** October 24, 2009, 01:35:15 PM »

I dare say the cups set screw aint tight enough......

port1 · « **Reply #22 on:** October 24, 2009, 05:46:57 PM »

Nice setup on those anny's, Andrew.
Twins!

Henry

DanS · « **Reply #23 on:** October 24, 2009, 06:32:30 PM »

Quote from: Bashy on October 24, 2009, 01:35:15 PM

I dare say the cups set screw aint tight enough......

heh heh, or you could say he's running on 2 cups? Kind of like 1 fry short of a Happy Meal!

killwilly · « **Reply #24 on:** October 25, 2009, 03:26:46 AM »

Quote from: sam2004gp on October 22, 2008, 02:58:42 PM

The only way to calibrate it, as far as I have seen... Is to have a couple of other different brand of anemometers at your location, then you average them out. But that is not easy or cost effective to do.

Also there was once a thread at the old Ambient forum that stated that the WMR968's were notorously low in recording their speed. So in VWS, in calibration settings, change your gain from 1.00 to 1.25. So when you record 5.00 MPH on the console for example, VWS should read 6.25. 2nd example when you read 40MPH on the console, you get 50MPH in VWS. I did this and noticed that my average wind speeds seem to be more inline with the stations around me, per WU.

^^^^So this is what I am sticking with until someone can give a better answer. And if anyone has one, please respond here, and help us all out.

Sam, good advice as always. Should the 1.25 gain be made to the gust as well as the speed?

Alan.

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Author Topic: WMR 968 anemometer (Read 9393 times)