No rain / lots of rain / weather in general

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Re: No rain

Postby offgridQLD » Mon Sep 19, 2016 1:41 pm

That's a good soaking yet again Gordon. Looking at the pick at first I thought you had just loaded the ute up with green wast and just got a big carried away :lol:

Bpratt, The Davis VP2 6163 looks like a nice unit . Shame it's RRP is about 10x more than I was looking to spend ;)

The Stevenson Screen is the way to go if it's in direct sun. I will see how I go with a sensor mounted midpoint on my back deck. It's a large under cover area about 15m x 6m and open two sides so good air flow. if I mount suspended - hanging mid air (perhaps fishing line ) so its away from ceiling , walls and solid objects and in the shade. I have mercury gauge in that location now for outdoor temps and it seems to be giving a reasonable indication of true outdoor air temps.
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Re: No rain

Postby Gordon-Loomberah » Mon Sep 19, 2016 1:55 pm

Thats the same Wx station I have. Many of the cheaper units available are not very reliable and can be quite inaccurate too. Before the Davis I had a $450 La Crosse unit from the Weatherzone shop- it was useless rubbish.

Kurt, ideally your temperature sensor should be mounted in an open flat grassy area, 1.5m above ground. On the back deck you'll have other influences on the temperature, although it may well be close enough your purposes.
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Re: No rain

Postby offgridQLD » Mon Sep 19, 2016 3:09 pm

I have a spot for the unit in the open grass area for rain reading and (I guess ok for outside temp as long as the fan can combat the direct sun heat influence that i have had bad experience with before).

Though the wind reading wont be in line with what you should officially be recording. At 1.5m height in that location it would be reasonably sheltered from wind. Though it will show the wind at location, human and low structure height (height where it matters to me) rather than at the official recording height (what is it 10m or so?)

The biggest issue I have had with inaccuracy is temp meters that don't react to sudden changes predominantly due to thermal mass of the structure it's housed in. For example inexpensive clocks with built in digital temp gauges. Leave them to settle in a temp controlled environment and they will settle to a reading that is within .1C of a expensive fluke meter i have. Though as the temp changes, say night time they will hold there previous temp for bleeding it of over many hrs before reacting to the true temp. Again when being heated back up again.

If the weather station can give me temp readings within 1 deg C or so of true readings that's ok. Will keep tabs on it at first along side some better less automated metering kit I have

Rainfall within say 5% would be ok. Will keep a check on it along side the manual rain gauge for a while.

Wind, all I wouldn't be using it to get some idea of the wind gust speed during storms (rather than hanging offside of the deck saying...Sh*t look at the trees flex! I wonder how strong that wind is? :lol: )
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Lots of rain!

Postby Gordon-Loomberah » Mon Sep 19, 2016 3:20 pm

The 1.5m is only for temp/humidity readings, and yes wind should be at the top of a 10m tower in an open area. Of course that isn't possible everywhere, I have mine on a 6m tower, but there are plenty of trees around, and a 150m high hill immediately to the west!
I measured a 48km/hr gust in one of short downpours last night.
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Re: No rain

Postby offgridQLD » Mon Sep 19, 2016 3:52 pm

Well that 48kph gust is what matters to you at your house. Even if the true wind reading above in the open was 100kph unless your doing something or have something up at that height that reading wont effect you or would you ever feel it.
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Re: No rain

Postby Gordon-Loomberah » Mon Sep 19, 2016 4:33 pm

A 23m high tree could certainly feel it! However, there wasn't much wind at the time it fell, although the ground is saturated.
Actually even on a 6m tower, the anemometer is well below the house, due to us living on the side of a hill.
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Re: No rain / lots of rain / weather in general

Postby offgridQLD » Mon Sep 19, 2016 6:14 pm

Yes forgot your 1/2 up a hill Gordon. Im on the top but lots of tall trees around us so we hear the severity of the wind in the trees but don't get the full impact of the wind at the house.



Some digging I found the sensor used in the unit .

Sensirion SHT21

The accuracy from temp in the 0C - 50C range that would need at my location is is +/- 0.2C. Relative Humidity is +/- 3% in the 20% - 80% range then ramps up to +/-4% for the upper and lower 20%..

Looks like the internal solar powered fan only lasts about 2 years max before its toast So might look at upgrading it first up to a High spec fan.
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Re: No rain / lots of rain / weather in general

Postby offgridQLD » Wed Sep 21, 2016 7:12 pm

The new weather station turned up today. I also got the $1 ebay broken rain gauge today to. The broken one is fixed already with just a new 20m x 2.2mm SS pin :D .

I did the calibration test on the new weather stations rain gauge though the results were bang on so didn't tweek the adjustment screws.

tip...use a spray bottle to distribute the calibration water measure.

I set it up along side the manual gauge and we had a few MM of rain this afternoon.

Manual gauge reading
Image

Digital gauge reading.
Image

I would like to see more rain say 50 - 100mm for more conclusive results.

The wind speed was tested driving the electric car with it out the window at various fixed speeds GPS comparison . I would trust it to 100kph to be close enough :lol:

Temps I need to spend some more time on over the next few days when I can compare it to known to be accurate meters.

Nice to have data logging activated and my homes weather being logged now.

I will update a link to my data stream when I am happy its some what accurate soon.

Kurt
Offgrid 2008, Selectronic PS1 6kw/48v inverter, x 2 Midnite solar classic 150 MPPT, 3960w NE PV 24 x 165w BP panels, 4200w NW PV 21 x 200w DAQO PV, 16x400ah lithium.
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Re: No rain / lots of rain / weather in general

Postby offgridQLD » Sat Sep 24, 2016 8:48 pm

I got my personal weather station up and running live feed to weather Underground tonight . It's updating every 5 min or so.

my station link
https://www.wunderground.com/personal-weather-station/dashboard?ID=IREESVIL2#history

I am trying to hack a old 7" windows 8 tablet to run from a mains 5v ac/dc power supply (without the internal lithium battery) so I can keep the app running 24/7 for data logging to WU with low power consumption.

See how we go.

Edit:
Issues I have noticed to date. One being the location 1.5m off the ground the wind direction indication is a little erratic due to the disturbed air at that low height.

It seems we get lots of small shifts in air temp a fraction of one deg C due to the cool air in the valley blowing op in little breezy gusts. I noticed this a lot with my fluke meter taking samples as it reacts instantly to change in air temp. . I added some shielding to the weather station no smooth this out some.Most times its ok on the weather station but some times a sample is taken and logged just as a big gust of valley air blows up dropping the air temp a fraction . Followed by completely still conditions.

Gordon, how is the averaging on your systems temp reading do you get small fluctuations say 15.3....15.2....15.1 then back to 15.3 in the evening over short periods (say 25mins) I think its due to cool air pockets shifting by. Or is the sample rate longer spaced and perhaps better averaging? I have noticed the same up down variation on other stations in the hills.

example
Image

Kurt
Offgrid 2008, Selectronic PS1 6kw/48v inverter, x 2 Midnite solar classic 150 MPPT, 3960w NE PV 24 x 165w BP panels, 4200w NW PV 21 x 200w DAQO PV, 16x400ah lithium.
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Re: No rain / lots of rain / weather in general

Postby Gordon-Loomberah » Sat Sep 24, 2016 11:28 pm

The sampling period in your logging is a bit random Kurt ;) but yes on 5 min time scales it can go up and down a tenth of a degree or 3 on some days, and on others it is very steady, it really depends on wind and radiation levels, and rain etc. Sometimes it can drop 10C in under half an hour in a storm!
I log at 1 min intervals and there is no smoothing on the graphs, and I don't think there should be, as that's how the temperature really does vary.

If you plot with a thick enough line, all the little wiggles will vanish :lol:

PS, I see you need to calibrate your barometric pressure with a sea level correction so that you can compare with other stations.
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