What I am planning & a few doubts

What I am planning & a few doubts - Printable Version

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RE: What I am planning & a few doubts - jomimota - 25-05-2015

(25-05-2015, 10:09)hvalentim Wrote: RX unit case dimensions are 120x70x50mm & 120x70x30mm (second is LCD w/ transparent cover).

Brand "Kemo". Purchased from Mauser.pt.

Specifically:
Caixa plástica com tampa transparente 120x70x30mm - Kemo G091 (used for LCD)
Caixa plástica 120x70x50mm - Kemo G086 (used for main board)

Thank you.

my external setup - hvalentim - 28-05-2015

A few pic.s of my current external gear setup.

[Image: two_masts.jpg]

Still missing the UV/Solar Rad box, probably to be applied on top of the FARS.

RE: What I am planning & a few doubts - werk_ag - 28-05-2015

Nice pictures. A pro installation!

RE: What I am planning & a few doubts - hvalentim - 29-05-2015

(28-05-2015, 23:04)Werk_AG Wrote: Nice pictures. A pro installation!

Thanks. Still, there is room for improvement with a second TX.

Wind sensors are placed per WMO recommendations:

"standard height of 10 m above open terrain is specified for the exposure of wind instruments."

But the rain-gauge may be too exposed:

"Ground-level gauges are used as reference gauges for liquid precipitation measurement. Because of the absence of wind-induced error, they generally show more precipitation than any elevated gauge (WMO, 1984). The gauge is placed in a pit with the gauge rim at ground level..."

As well as the temp/hum sensor:

"For general meteorological work, the observed air temperature should be representative of the free air conditions surrounding the station over as large an area as possible, at a height of between 1.2 and 2.0 m above ground level. The height above ground level is specified because large vertical temperature gradients may exist in the lowest layers of the atmosphere. The best site for the measurements is, therefore, over level ground, freely exposed to sunshine and wind and not shielded by, or close to, trees, buildings and other obstructions. Sites on steep slopes or in hollows are subject to exceptional conditions and should be avoided. In towns and cities, local peculiarities are expected to be more marked than in rural districts. Temperature observations on the top of buildings are of doubtful significance and use because of the variable vertical temperature gradient and the effect of the building itself on the temperature distribution."

Of course the ideal must meet the feasible somewhere and if one did take WMO recommendations to the letter, keeping a weather station would become a real estate project (see attached schema).

Also, the requirements to qualify to be Class 1 temp/hum installation are:
"Class 1
(a) Flat, horizontal land, surrounded by an open space, slope less than ⅓ (19°);
(b) Ground covered with natural and low vegetation (< 10 cm) representative of the region;
© Measurement point situated:
(i) At more than 100 m from heat sources or reflective surfaces (buildings, concrete surfaces, car parks, etc.);
(ii) At more than 100 m from an expanse of water (unless significant of the region);
(iii) Away from all projected shade when the sun is higher than 5°."

I find particularly problematic the idea that one should keep temp/hum instruments over grass. I do have some grass around but how I am (or anyone) supposed to keep it without watering at least in Summer?

RE: What I am planning & a few doubts - Brett - 30-05-2015

the point about grass is that the alternatives like concrete are very heat reflective and will get lots of increased ambient temperature. The local football club won't take kindly to you setting up the unit in the middle of the field on the halfway line and marking a no-watering zone around it, will they Smile

But for complete accuracy (or more correctly, consistency), that's the kind of location that you need. Ultimately, compromises will always need to be made in a home setting. Aspirated sensor units can help (if you can aspirate from "non-tainted" sources) but the compromise is if you want weather condition information you'll need to find the least impactful location for your sensors or like me, put up with knowing you have them in a problem area, but knowing it's still correct "relative" to the reading you took 5 mins ago (but maybe not to the local airport with proper sensor placement)

RE: What I am planning & a few doubts - JT118 - 30-05-2015

(30-05-2015, 01:26)Brett Wrote: the point about grass is that the alternatives like concrete are very heat reflective and will get lots of increased ambient temperature. The local football club won't take kindly to you setting up the unit in the middle of the field on the halfway line and marking a no-watering zone around it, will they But for complete accuracy (or more correctly, consistency), that's the kind of location that you need. Ultimately, compromises will always need to be made in a home setting. Aspirated sensor units can help (if you can aspirate from "non-tainted" sources) but the compromise is if you want weather condition information you'll need to find the least impactful location for your sensors or like me, put up with knowing you have them in a problem area, but knowing it's still correct "relative" to the reading you took 5 mins ago (but maybe not to the local airport with proper sensor placement)

An idea is to use a nearby airport metar at as a comparison. I use Prestwick airport, I am 15 km from there and 100m higher, so take that into account. Also.my barometer readings are not corrected for elevation and soil temp is actually house temp, I cannot work out a way of changing the names in the software,
See www.ayrshireweather.org

RE: What I am planning & a few doubts - hvalentim - 19-10-2015

Well, a recent episode of strong wind-gusts proved that the idea of placing a rain meter on a pole is wrong by design. Under extreme conditions the pole will always wobble a bit and they will make the rain-meter tip artificially.