Accuracy of a WH3081

[gpercival]

I am considering buying a model WH3081. I am reading conflicting specifications for this model. Can anybody who owns one tell me what the accuracy of the humidity and rain sensors are?

Geoff

[jim-easterbrook]

I've not seen any claims for accuracy. The resolution of the humidity sensor is 1% and of the rain sensor is 0.3mm. I would estimate the accuracy of the humidity sensor to be around 5% (based on the different readings from two adjacent sensors). The rain sensor's main problems are related to rain bouncing out etc.

[AllyCat]

Hi Geoff,

Yes, I have a 308x (actually the 3080 which has a Radio Controlled Clock) so can quote FO's figures from the User Manual:

Temperaure Accuracy +/- 1 degree C
Humidity +/- 5%
Rain +/- 10%.

However, those are the manufacturer's figures, some of which are rather dubious, such as the wireless range of 100 metres and Lux accuracy of +/- 15% ! Others have questioned the wind accuracy (e.g. Steve), rain accuracy (due to "splash out") and personally I consider the UV reading (at least of my unit) to be "garbage".

In Australia, the 3081 seems to be the "standard" FO model, selling at a similar price to the non-Solar models (that are more common) here in the UK, which is surprising with our current exchange rate. So beware that some ebay sellers may be "shifting stock", since there are a number of "known issues" with the 308xs (search this forum).

However, despite all of the above, IMHO these FO stations still offer good value for money, provided that you are prepared (and able) to check their calibration and return/exchage them with the seller if necessary.

Cheers, Alan.

[MickinMoulden]

WS1081 will read humidity down to 10% (manual says 1%) otherwise mine reads pretty spot on with others. Not sure if the model you want will be the same or not in regards to humidity readings, but it is something to consider if you live in a fire danger area (and wish to run a website with fire danger index calculations) or an area of low humidity at times (check local historic records) and you wish have your stats read true (I would). Rain gauges will read low due to blow out, so just modify it. It can be calibrated with a manual rain gauge and Cumulus (which you should do with any brand or model IMO).

[philcdav]

Hi Geoff.

Agree with the previous comments but would also add that the sensor location and containment will probably effect results more than anything else.

You really need a Stevenson screen, an 'out in the clear' anemometer location and wind free mod for the rain collector.

All achievable but at what cost and for how much more accuracy?

Bottom line for me is that its a hobby based on relatively cheap equipment.

If you really want accuracy the you need to spend a lot more

[AllyCat]

Agree with the previous comments but would also add that the sensor location and containment will probably effect results more than anything else.

Hi,

Yes indeed, and that highlights one of the several bad "design decisions" made for the Solar additions of the 308x compared with the original 108x weather stations. The Solar Pod has a short cable which is captive (permanently attached) to the "Sun Shield" and plugs directly into the temperature/humidity/transmitter module. But in most cases it is desirable (perhaps essential) to mount the Solar sensors at the top of a mast (i.e. with the wind sensors) whilst the temperature/humidity and rain sensors should be near to ground level. To compound the "error", the rain sensor cable plugs into a socket on the Solar Pod!

I have extended the cable on my Solar Pod but have not yet "published" modification instructions, because it required the use of a soldering iron, and/or at least a crimping tool for RJ12/45 sockets. Then there are still the physical modifications required for mounting the separate modules and improving the (almost useless) original sunshield.

Cheers, Alan.

[peterh]

Hi Allycat,

Why would the solar pod have to be mounted on a mast?

Re: extension of the solar pod cable: it could probably be done fairly easy by using an RJ45 extender (basically this is a small "block" containing two RJ45 receptables) and a straight cable. If the extension is done this way, it would definitely be mandatory to fully cover the extension point (the extender and the connectors) in isolation paste. As I haven't seen any need to put my solar sensor high up, I haven't experimented with this.

I, for one, am fully supportive of replacing the useless radiation screen in favour of a Stevenson screen. My station has been in use since December 2012, so it hasn't seen anything remotely resembling summer yet. Yet, I have seen temperature differences as high as 5° C.

[AllyCat]

Why would the solar pod have to be mounted on a mast?

Hi Peter,

So that the sensor can "see" the sun directly at low elevations (e.g. near sunrise and sunset) to determine "is the sun shining?". Otherwise there's a risk that it may be a "white cloud" detector not a sunshine detector.

The connector on the solar pod is actually a 6 pole RJ12 connector, which will indeed plug into a RJ45 (8 pole) socket/coupler (but not vice versa). However, the contacts may not align very well as the central latch is not really intended to prevent lateral movement. Also, FO use a "ribbon" (parallel conductors) cable rather than the twisted pairs of CAT5 cable, which may behave rather differently in long lengths. But I doubt if this is very significant for the solar pod cable (it might be for the wind cable on non-solar models).

Yes, I located my "transmitter" and sunshield in a "shady" location, but it catches the early morning sun and typically I see a 5 degrees "spike" on sunny mornings.

Cheers, Alan.

[ArjanH]

Hi Guys

I am completely new to this weather thing but somehow ended up with a WH3081 from TradeMe (NZ's equivalent to Ebay) for $120NZ.
I even managed to get it online without any issues. But after two days of monitoring I have a few questions.

Firstly, the rain bucket water bouncing out thing. It would be fairly easy to raise the rim around the outside with a bit of Eraldite and some plastic. The question is how much should I raise it by and am I going to effect the readings in some way I haven't yet considered?

Second, yesterday on only my second day of running and the first real bit of sun for some reason the light sensor seemed to jam up and stopped responding. All the other sensors continued normally but the light sensor stopped. Is this a common thing? It appears that today around about the same time of the day it suddenly stopped again but then started again. I am not sure if this is PC related or not.

Thirdly, I have my sensors located on the end of my mancave about 1.5 meters above the roof which is corrugated iron and painted a dark gray colour. I have a theory that the temperature spikes I recorded today have something to do with heat coming of the roof whenever the sun comes out. would this be a fair guestimate?

And lastly. If I do need to move the light, rain and Temp/Hum sensors I can soon make up some cables because that's pretty much what I do for a living however, does anybody know what the maximum runs are? I would like to keep the wind sensors exactly where they are but the other runs could be well over 20 meters.

Thanks

Arjan

http://www.wunderground.com/weatherstat ... IBAYOFPL26

[AllyCat]

Hi Arjan,

Welcome to the forum. Most of the answers are "yes" and can be found by searching this forum, but may not be easy to find.

There shouldn't be any "issues" in raising the sides of the rain gauge by a cm or two. Also, the general recommendation is to mount it as near to the ground as possible (but not shielded by buildings, etc.). Personally, I added a larger, steep-sided "funnel" above the gauge to increase the resolution to 0.1 mm (per tip).

Yes, there are many reports of the solar pod "going offline", but does yours actually start up again without assistance (resetting), which I think is unusual?

Yes, the FO "sun screen" is fairly useless, an additional 5 degree C rise is quite common when the sun strikes it.

And extending the cables is certainly possible. There are no known "absolute" limits, but you need to be wary of possible crosstalk or radio interference pickup and/or water ingress into the connectors, or damage to the cable by UV light.

Cheers, Alan.

[ArjanH]

Hi Arjan,

Welcome to the forum. Most of the answers are "yes" and can be found by searching this forum, but may not be easy to find.

There shouldn't be any "issues" in raising the sides of the rain gauge by a cm or two. Also, the general recommendation is to mount it as near to the ground as possible (but not shielded by buildings, etc.). Personally, I added a larger, steep-sided "funnel" above the gauge to increase the resolution to 0.1 mm (per tip).

Yes, there are many reports of the solar pod "going offline", but does yours actually start up again without assistance (resetting), which I think is unusual?

Yes, the FO "sun screen" is fairly useless, an additional 5 degree C rise is quite common when the sun strikes it.

And extending the cables is certainly possible. There are no known "absolute" limits, but you need to be wary of possible crosstalk or radio interference pickup and/or water ingress into the connectors, or damage to the cable by UV light.

Cheers, Alan.

Thanks Alan

I will hunt around and do a bit more reading. I figured shouldn't be too many issues with that part. My readings aren't too far apart from another station on the other side of town with a Vanatage pro. Given the distance and location difference and the fact that most of the difference happened in a short space of time my thoughts were that he just had more rain in the morning.
What would the advantage be with having the rain collector close to the ground? I can think of several disadvantages including certain 6 year olds who just love to "investigate" and "accidentally" taking things apart.
The light sensor is much more of a worry. I mounted the entire suit where it is because it is relatively easy to get at and in the clearest air for my property. This doesn't mean I want to go climbing up there every day to reset the bloody thing. Something will need to be done about that. I will do some reading and post and action taken.

Cheers

Arjan

[AllyCat]

Hi Arjan,

The most important factor is that the rain sensor needs to be mounted solidly because any movement (high on a mast for example) can cause excessive rainfall readings. Ideally, it should be near ground level because wind at higher elevations is said to cause under-reading (but IMHO it's a relatively minor factor).

If you have one of the "locking up" Solar Pods (which can't be exchanged for a "good" one) the best advice (currently) appears to be to reduce the light level reaching the Lux sensor (white dome) by about 50% and then compensate the value accordingly within Cumulus.

Cheers, Alan.