You're missing a time constant there. 2.5 mph per revoution per ???? A single revolution or a single pulse has a measurement uncertainty of +/- 12.5 % with 8 ppr. So if you're going to measure veloc
There's hot wire anemometers which can have very fast response times (milliseconds or less), but which require a bit more calibration, and are sensitive to ambient temperature. This, for those that d
Sorry, the calibration factor is 2.5 mph per revolution per second. I got sloppy when I typed that, although I would have thought that was almost intuitively obvious. But your +/- 12.5% assertion is
I don't think it's misleading, but you'd have to look at my prior post. If you're going for a "fast" measurement technique, you can measure the time between two pulses. If you do that, the absolute p
That's all true, but that doesn't mean it is at all relevant. At 25 mph, that anemometer with eight points of resolution per revolution has all of 12.5 milliseconds between pulses. Unless you're tryi
Al is exactly correct in his assessment. Meteorologists (like me) worry about this stuff all the time. If we want to measure the turbulence spectrum down to the eddy dissipation rate, we need extreme
No ... Al is not correct in his assessment, at least not at a practical level. The 12.5% "inaccuracy" he claims is purely arbitrary ... it's a 12.5% inaccuracy for one revolution, which is meaningles
I'm not going to belabor the point. Wind speed is derived by measuring the change in rotational position divided by time. The shorter the sampling interval (time), the lower the measurement accuracy.
I also think Al's math is incorrect. My frequency counters measure intervals to nanoseconds, better ones can to picosecond resolution, these are standard features on better frequency counters. So one
not true. Consider a frequency counter in your shack. You can have a particular gate time and count positive zero crossings during that gate. For this simple scheme, yes, short measurement gate mean
This is the key thing that misses the entire point. It's not the accuracy of the time measurement that's the issue. It is the uncertainty of when position transitions are crossed. With either electr
This is the key thing that misses the entire point. It's not the accuracy of the time measurement that's the issue. It is the uncertainty of when position transitions are crossed. With either electro
Sigh. That initial degree of uncertainty only exists for 12. 5 milliseconds at 25 mph (80 pulses per second). How is that even the least bit relevant here?? No way a tower or its antennas respond mec
Author: "Roger (K8RI) on TT" <K8RI-on-TowerTalk@tm.net>
Date: Wed, 30 Apr 2014 01:34:13 -0400
On 4/29/2014 9:59 PM, Jim Lux wrote: On 4/29/14, 5:08 PM, Al Kozakiewicz wrote: I'm not going to belabor the point. Wind speed is derived by measuring the change in rotational position divided by tim
and accuracy compared to what, and over what period?? wind speed is HIGHLY variable over small distances and elevation change. There are specifications for measuring wind that require so much open ar
I really have a problem with the big fans, several hundred locally, that blow almost constantly around EN50nj. (tongue firmly in cheek) 73 & DX, Gary - AB9M --Original Message-- From: David Robbins S
Steve, FWIW, for the past 7-years I have operated the Davis Pro-2 "Wireless" Weather Station near my radio and tower with absolutely no problems and no RFI. I was very concerned about the possibility
Author: GEO Badger via TowerTalk <towertalk@contesting.com>
Date: Wed, 30 Apr 2014 14:52:13 -0700 (PDT)
I believe I have missed something here. Basically, what is the problem statement? Measuring and/or logging wind speed/direction? Early warning in order to be able to lower a tower? Of course one woul
The fans at http://en.wikipedia.org/wiki/File:Twin_Groves_Wind_Farm_DSC03252.JPG -- 85 foot blades on 270 foot tower. I really have a problem with the big fans, several hundred locally, that blow alm
I think that anemometers are an interesting topic but it appears this one has been beat to death and I'm not sure why this is even a topic for TT. Is it because it is attached to a ham radio tower? I