Author Topic: Sensor location for new station  (Read 2421 times)

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Offline docsquic

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Sensor location for new station
« on: July 31, 2009, 09:51:07 AM »
HI,

This is my first post.  I'm in the process of purchasing a VP2+.  I'm just trying to get all of the specs and info before actually purchasing it.  My primary concern right now is the mounting location.  I'm going to put it at my office since it is located on the top of a hill which should be good for wind measurement.  From what I can see, the best place to mount the ISS and anemometer will be the aluminum light post behind the office since it is taller than the building (approx. 30 feet tall).  I'd like to place the anemometer on top of the post but my concern is that there are two halogen light heads there which would probably interfere with the wireless transmission.  My solution (just guessing here because I don't have the unit yet) would be to extend the transmitter well below the lights via shielded extension cable of some sort and thereby avoid the potential interference.  Is this doable with the anemometer?  I was also planning to mount the ISS to the pole via a custom mounting bracket at about 10 ft. or so to keep it "out of harms way" so to speak since this is a public place.  That way it could be serviced as needed and not stolen or vandalized while no one is there.  I'd use the roof but I'm not a big fan of going up on roofs since I passed 55  ;) .  I can have the lighting company that changes the halogen lamps use their cherry picker to place the the anemometer and do the cable.  For the ISS I can just use a ladder when needed.  I'm just mulling ideas at this point so any suggestions would be very helpful.

Thanks,
Mark

Offline racenet

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Re: Sensor location for new station
« Reply #1 on: July 31, 2009, 09:58:35 AM »
Yes, the anemometer & ISS can be 40' apart. That is how much cable they provide. If you need more distance, you can extend that lenght.



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Offline wxtech

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Re: Sensor location for new station
« Reply #2 on: July 31, 2009, 10:11:51 AM »
As Bob said the anemometer is connected to the ISS via 40' phone cable, not transmitter.  You may need to shield that cable if the lamps produce noisy transitions.

I recommend the ISS be on its own pole not on a tall light pole.  Unless you put it on a bracket extended away from the pole to minimize the rain shadow effect of the large diameter light pole.  The ISS and rain gauge need to be serviceable for cleaning.

Suggestion, try mounting the anemometer and ISS all together on your special bracket.  If you believe the winds are disrupted by obstacles, then get it moved to the top of the pole.
Al Washington, Lexington, Ga.,  NWS Coop station=LXTG1, Fischer Porter, SRG, MMTS. 
CoCoRaHS=GA-OG-1. CWOP=CW2074.  Davis VP2+ WLIP 5.9.2, VP(original) serial, VWS v15.00 p02. ImageSalsa, Win7 & Win8 all-in-one.

Offline docsquic

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Re: Sensor location for new station
« Reply #3 on: July 31, 2009, 10:26:33 AM »
Thanks for the reply's,

I realized after my first post that the ISS is the transmitter for the anemometer also.  I was planning to make a mounting bracket to move the ISS far enough away from the post to eliminate the rain shadow (the post is about 8" dia at the level I would use).  Because of the location, about 20 feet behind the building, I would have to extend the anemometer to the top of the post for accuracy.  I agree with wxtech about the shielding.  The lights are only on for about 4 hours a day but why take chances.  As usual, this is an evolving project.  I'll keep everyone posted as things come together.  Great forum!

Mark

Offline wxtech

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Re: Sensor location for new station
« Reply #4 on: July 31, 2009, 10:35:35 AM »
I don't think a Halogen will be as noisy as a Mercury vapor.  But the high surge when the lamps turn on may induce a small voltage in the phone wire that Davis uses to the anemometer.  The voltage used on the anemometer is less than 3 volts.  Have the installers put the Davis phone wire anemometer cable inside a metal conduit grounded well.  If the heavy surge current to the lamps induce a voltage in the anemometer cable, that may give erroneous wind speeds as well as possibly damage the ISS.
The lamp wiring will be inside the aluminum pole but be safe and shield the wx sta wiring.
Al Washington, Lexington, Ga.,  NWS Coop station=LXTG1, Fischer Porter, SRG, MMTS. 
CoCoRaHS=GA-OG-1. CWOP=CW2074.  Davis VP2+ WLIP 5.9.2, VP(original) serial, VWS v15.00 p02. ImageSalsa, Win7 & Win8 all-in-one.

Offline docsquic

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Re: Sensor location for new station
« Reply #5 on: July 31, 2009, 10:53:37 AM »
Thanks wxtech,

I have a friend who is an electrical engineer that I can consult about the fine points of the shielding etc.

Mark

Offline W3DRM

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Re: Sensor location for new station
« Reply #6 on: July 31, 2009, 02:24:04 PM »
You could also replace the existing anemometer wiring with CAT-5 wiring (which is shielded) to eliminate any issue with external interference from the halogen lighting system. However, I rather doubt you will have any problem at all with the lighting system.

I would not worry about it unless you find there is a problem after you install the equipment. Of course, working on stuff at the top of a light pole isn't my idea of fun either...

Don - W3DRM - Emmett, Idaho --- Blitzortung ID: 808 --- FlightRadar24 ID: F-KBOI7
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Offline docsquic

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Re: Sensor location for new station
« Reply #7 on: August 01, 2009, 10:41:53 AM »
Good idea W3DRM,

I have a spool of shielded cat 5 plenum cable from a previous project that should do the trick.  I've never been shy about hacking new hardware if it improves the usability.

Thanks,
Mark

Offline docsquic

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Re: Sensor location for new station
« Reply #8 on: August 07, 2009, 04:21:51 PM »
Another question comes to mind. 
How critcal is it that the ISS be only approx 6ft. off of the ground?  In another discussion the topic of vandalism came up and I'm concerned about this since I'll be mounting it at a comercial site that is unattended evenings and at night.  I was planning to elevate the Iss at least 10ft. off of the ground for safety.  Will this adversely affect the accuracy of the Iss readings?

Mark

Offline d_l

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Re: Sensor location for new station
« Reply #9 on: August 07, 2009, 05:14:02 PM »
From my experience with two neighboring ISS stations that I monitor to compare to mine, it definitely can make a big difference as far as the heat up, cool down, max, and min temperatures.  Some of these differences are due to the type of surface under the ISS and the openness or sheltering nature of surrounding structures or vegetation.

My station is 6 feet up over native brushy vegetation and bouldery soil.  One of the other stations is about 10-12 feet up over an unknown surface (it is behind a privacy fence) and the other is about 22-25 feet up over a garage roof. 

My station typically is 3 to more than 5 degrees colder in the morning due to its location closer to the heat-radiating soil and brush surfaces.  Those higher up are kept warmer by night breezes too.  So there is a micro temperature inversion factor at work here at night if the air is clear.

In the morning, my station heats up more slowly if the air is still because it has a FARS (the other two don't) and there is shading of the surface directly under it. If there is wind, all the stations tend to read the same temperature.  By the afternoon, my station heats more than the other two because of solar radiation that is re-radiated from the soil underneath. Once the sun sets and the evening breezes subside, my station then cools down much faster than the others.

So I think a lower mounted station in any location might have more extreme temperature ranges, but the daily average should be very close to the same as those mounted higher.
--Dave--

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People always talk about the weather, but they never do anything about it.  Not me.  I'm gonna measure it.  https://www.tceweather.com

Offline docsquic

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Re: Sensor location for new station
« Reply #10 on: August 07, 2009, 06:08:30 PM »
Thanks d_l,   I'll consider that in my site search.  I have an empty lot behind my building that is usually grass covered.  I was going to mount the ISS on an aluminum light post that is about 20ft behind the building and on the edge of the vacant lot.  I had assumed that the FARS would mitigate any thermal variances due to reflectivity or surface radiation, but it seems that was not an accurate assumption.

Mark

Offline d_l

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Re: Sensor location for new station
« Reply #11 on: August 09, 2009, 03:13:33 PM »
I had assumed that the FARS would mitigate any thermal variances due to reflectivity or surface radiation, but it seems that was not an accurate assumption.

I think it does that as well, but mostly it keeps the thermometer in equilibrium with the outside air temperature.

The radiation shielding does heat up when the sun angle is low and the rays are hitting more directly on the sides of the shelter rings.  This is especially noticeable in the mornings here.  Without the FARS airflow, I think there is faster warm up happening inside the thermometer chamber due to conduction through the rings.  In the afternoons, we always have some winds causing airflow into the chamber so the FARS isn't as necessary.

If the surfaces under the ISS heat up from sunlight and then warm the local air in the vicinity of the station, the FARS is simply going to bring the station in equilibrium with that heated air that much faster.
--Dave--

Wireless VP2 w/ solar, 24hr FARS, Heater, (Envoy-WLIP)*3-Meteohub, plus custom VP2 @ 26', WL 6.0.4, WU & W4U=KNVRENO37 NetcamXL

People always talk about the weather, but they never do anything about it.  Not me.  I'm gonna measure it.  https://www.tceweather.com

 

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