>but at 2.5 mph per revolution and 8 pulses per revolution
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 velocity by measuring the time
between two consecutive pulses (the smallest possible sample), your accuracy is
never going to be better than that. But response time will be fast.
Al
AB2ZY
________________________________________
From: TowerTalk [towertalk-bounces@contesting.com] On Behalf Of David Gilbert
[xdavid@cis-broadband.com]
Sent: Monday, April 28, 2014 1:26 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Wired Anemometer for Tower?
Not to pound the InSpeed drum, especially since I have no connection to
them at all other than as a long ago customer, but InSpeed also sells a
high resolution anemometer for $89 that puts out 8 pulses per
revolution. The response of either Vortex version is of course limited
by the time between pulses, but at 2.5 mph per revolution and 8 pulses
per revolution for the hi-res version the ability to almost instantly
track wind gusts would be limited primarily by the mass of the rotating
cups (no spec that I am aware of) ... and they are very light weight.
73,
Dave AB7E
On 4/27/2014 9:23 PM, Kim Elmore wrote:
> I can't speak to the Pro2 model, but any anemometer must average over a
> period. I was incorrect about the Vue: it yields 4 s averages in each packet.
> Sonic anemometers average over something like 10 pulses. Depending on the
> brand, that's anywhere from 1 s to 0.1 s. So, if you really need wind speed
> resolution better than 2 or 4 s, you need to obtain a sonic anemometer.
> Because of the mass of our antennas and towers, I'd be surprised if they have
> a significant response to frequencies much higher than 0.25 to 0.5 Hz, but to
> know that requires an engineer's analysis.
>
> Low-end sonic anemometers can be had for a few thousand dollars. They can,
> however, require periodic maintenance due to bird pecks (birds peck at the
> transducers) and bird droppings that contaminate the transducer surfaces.
>
> If you must have higher resolution than this you need very deep pockets
> indeed and a lidar anemometer.
>
> As for radar: the NEXRAD (WSR-88D) requires 5 min to complete a volume scan,
> but the latency for each radial of data is on the order of a second or so.
> So, it's available in real time. Thus, there's no significant latency once a
> volume is complete. It does take a few seconds to move the antenna back to
> the 0.5 deg elevation and start the next volume, but it moves pretty fast in
> elevation -- several degrees per second.
>
> Kim N5OP
>
> "People that make music together cannot be enemies, at least as long as the
> music lasts." -- Paul Hindemith
>
>> On Apr 27, 2014, at 22:29, "tomkd8deg" <kd8deg@centurytel.net> wrote:
>>
>> The unit I have is the Davis Vantage Pro2 wired, and the 4 second delay is
>> what Davis tech support told me when I questioned the accuracy of the wind
>> readings that were being displayed.
>>
>>
>>
>> Tom KD8DEG
>>
>>
>>
>> From: Kim Elmore [mailto:cw_de_n5op@sbcglobal.net]
>> Sent: Sunday, April 27, 2014 8:08 PM
>> To: tomkd8deg
>> Cc: EZ Rhino; <towertalk@contesting.com>
>> Subject: Re: [TowerTalk] Wired Anemometer for Tower?
>>
>>
>>
>> I'm not sure that's true about the wind. I have a Davis Vantage Vue. The
>> remote unit does some processing to generate a 2 s mean speed and a peak
>> gust value within the 2 s window. Data are then sent in packets every 2 s to
>> the base unit.
>>
>>
>>
>> Mine is up 10 m (a WMO standard height). During calm winters nights it will
>> measure an anomalously high minimum temperature. The anemometer is shielded
>> a bit by the tower structure when it's downwind of the tower and so the wind
>> speed is biased low. Direction appears unaffected.
>>
>>
>>
>> The rain gauge is a tipping spoon with a 3" diameter catchment. It under
>> samples only at high rain rates. The temperature sensor and dew cell are not
>> aspirated in this unit and so temperature is biased a bit high due to
>> radiation errors on calm, clear Summer days.
>>
>>
>>
>> I highly recommend any of the Davis units, but the Peet Bros. Ultimeter 2100
>> is also a very fine unit. Both are comparable in price (~$400).
>>
>>
>>
>> Kim N5OP
>>
>> "People that make music together cannot be enemies, at least as long as the
>> music lasts." -- Paul Hindemith
>>
>>
>> On Apr 27, 2014, at 18:29, "tomkd8deg" <kd8deg@centurytel.net> wrote:
>>
>> The Davis wired version, which I am using, has a 4 second delay for wind,
>> and direction display. That can mean the loss of 10 to 20 mph in a gust
>> situation.
>>
>> Tom KD8DEG
>>
>> -----Original Message-----
>> From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of EZ
>> Rhino
>> Sent: Sunday, April 27, 2014 4:10 PM
>> To: towertalk@contesting.com
>> Subject: Re: [TowerTalk] Wired Anemometer for Tower?
>>
>> I should mention one other thing about the "cheap" weather station
>> anemometers that drive me crazy. The first WX station I had only updated
>> the wind speed about every minute. The LaCrosse updates about every 12
>> seconds. This is almost worthless...I want to know the wind speed NOW! The
>> stuff from Inspeed is real time, very nice.
>>
>> Chris
>> KF7P
>>
>>
>>
>>
>>
>>
>> On Apr 27, 2014, at 14:03 , Roger (K8RI) on TT wrote:
>>
>> On 4/27/2014 3:15 PM, EZ Rhino wrote:
>>
>>
>>
>> I have tried a few different weather stations, so I can unequivocally tell
>>
>> you what NOT to get.
>>
>>
>>
>>
>>
>> DON'T buy anything under $300. *sigh*
>>
>>
>> Mine cost 40 something, works fine, is made of cheap plastic. Uses plain old
>> Duracell non rechargeable. Last 2 years or more outside. The ones indoors
>> only last 6 mo to a year. Probably cost twice that much now...if available
>>
>> Mounted on the tower where I can just reach it with an 8' stepladder.
>>
>> Does nothing except report wind speed, direction,temp, humidity, and
>> relative temp.
>>
>> 73
>>
>> Roger(K8RI)
>>
>>
>>
>>
>>
>>
>> Unfortunately the cheap ones are total garbage. The recent one I got is a
>>
>> LaCrosse station, purchased from Costco. Junk! Junky cheap plastic, the
>> rechargeable batteries in the solar powered wireless anenmometer/wind vane
>> unit went bad in the first year, and the rain bucket stopped working in the
>> first few months after purchase.
>>
>>
>>
>>
>>
>> The Davis units are good, have a buddy with one and it is quality stuff.
>>
>> And about $300. You pay for what you get. I agree, I think the wired units
>> are more reliable and last longer.
>>
>>
>>
>>
>>
>> Ok now take a look here: www.inspeed.com These guys make anemometers
>>
>> that are decent quality and not expensive. They also have a cool computer
>> hookup version that allows your PC to track all the data and put it in a
>> spreadsheet. AND it has the wind switch option, where you can program the
>> system to turn an appliance on or off (read: lower your tower!) if the wind
>> goes above a preprogrammed speed. Pretty neat. I don't have this option
>> yet. I think AB7E has one of the inspeed units too, maybe he can provide
>> some feedback.
>>
>>
>>
>>
>>
>> Chris
>>
>> KF7P
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> On Apr 27, 2014, at 11:01 , Steve Jones wrote:
>>
>>
>>
>> Can any of you recommend a wired anemometer or weather station unit?
>>
>>
>>
>> I want to install an anemometer to monitor the wind speed at the top
>>
>> of my tower. All I can find online are wireless units. On this
>>
>> reflector I have seen a number of bad reviews of wireless weather
>>
>> sensors, because their little wifi transceivers get damaged by the RF
>>
>> from a ham antenna. I have a spare CAT5 cable at the base of the tower
>>
>> available.
>>
>>
>>
>>
>>
>> 73,
>>
>>
>>
>> Steve
>>
>> N6SJ
>>
>>
>>
>>
>>
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