Sandaysoft

Hi
My La Crosse 2306 temp hum sensor is located at the top of a north facing window which measures overnight temps well but very high daytime temps. I plan to move this sensor tomorrow morning to a west side patio with the back of a garage to the west. When I set up this station a few months ago I placed it on the north side to capture the overnight temps that a another La Crosse station I have had for alomst 2 years that is located at this patio didnt record as well. I hope that this does not compromise the overnight temps too much but I am sick of getting 36 when it only 32. My question is should I disconnect the outdoor sensor form the inside receiving unit during the move of the sensor, any experiences with moving a sensor and if so would that have any effect on the readings with Cumulus, in particular the rain and its counter. Or is there is no point doing this. I have not moved a sensor before as the other La Crosse that I can't use with Cumulus have never been moved. Details of my two La Crosse stations is here: viewtopic.php?f=15&t=6395. This is only spot near my wind sensor that could have a balance between good daytime and overnight temps because the wind sensor can't be moved as that is the only good spot.

Thanks

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Regards, Matt of Brisbane, Australia
Web Site: http://www.localweatherdata.0glo.com

If moving the temperature sensor also involves moving the rain gauge, then you will definitely get spurious rain figures. I don't know enough about La Crosse stations to be able to advise what you have to do to avoid this, though. No doubt someone else will be able to advise.

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Steve
Sanday Weather
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The temp hum sensor connects to the receiving unit via wireless and the wind and rain to the temp and hum via cable. I am only moving the temp hum but disconnecting will stop all outdoor transmission. Is there any point in disconnecting for the trouble it will cause. Thanks Steve for your quick answer.

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Regards, Matt of Brisbane, Australia
Web Site: http://www.localweatherdata.0glo.com

Well I am going to move the sensor today and I think that the easiest way is to keep the sensors connected and if there are any bad readings just edit or delete them. Hopefully this will improve my readings.

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Regards, Matt of Brisbane, Australia
Web Site: http://www.localweatherdata.0glo.com

Update on moving my sensor. I did move my sensor and I placed at the west side patio but on the edge closest to the outside so that I don't get the bad overnight temp that my other station records also in the patio but much further in reads too mild. However because I placed it about 30 cm from the edge of the wall at this patio it recorded mild overnight temps and so only solved the day time temps which now read correctly because it out of the heat. I did test the new spot with a sensor form my spare Oregon Scientific station it did record the same daytime temps. I did not want to put it too close to the edge or it might get heat from the north side of the house. So today I gave it one more try to see if I could get perfect readings and I placed it 10 to 15 cm from the edge and I got it right. Absolutely perfect now because this evening it is recording a bit lower than the other station which it should be as like as it was at the top of the window on the north side of the house before I moved it . This is important because on a winter morning it can be up to 3 degree warmer in the patio and 1 degree at this time of year. This can be calculated but it is annoying. I almost gave up on this but I am glad it has worked, I was thinking what will I do to get this right, but after 22 months since I bought my first La Crosse, I got my newer one with Cumulus. I might even move that the original station as well. I finally did it and my figures are perfect now. Now I need to edit the bad temp readings. Just a question would sensors from two weather station interfere with each other but they are not on the same frequency if they are next to each other. I guess I give it a go.

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Regards, Matt of Brisbane, Australia
Web Site: http://www.localweatherdata.0glo.com

That was a false alarm because it was recording good but not good enough overnight temp readings. I have been careful to place not place it too close to the side of the wall closer to the north side of the house because I was concerned that it would create too high day temps which is does. I have been moving it closer and closer to this edge to get the readings for the overnight better and is almost perfect but the daytime is about 0.5 to 1.2 degree C higher. But I only moved it the lastest spot yesterday and so that statement is only based on overnight and today, I see how it goes tomorrow. The question is would it be acceptable to get the overnight temps right by a compromise of the daytime by up to 1.2 degree C. Is that not too much to worry about . Or should I aim to get the daytime temps right and have higher overnight temps which is up to 3 degree C in winter. Any comments or suggestions would be greatly appreciated. Thanks.

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Regards, Matt of Brisbane, Australia
Web Site: http://www.localweatherdata.0glo.com

Hi Matt.

you might have a look here for some info on 'siting' the sensors .. http://weatherfaqs.org.uk/node/124

I know its often a compromise but theres not much point in taking 'bad' readings.

A screen for the temp unit is ideal but often not easily achievable.

My complete unit is bolted to a garden shed at about 4.5 m. Its reachable for service but not ideal for wind measurement.

The temp unit has a 15 cm plastic flower pot glued over it. Painted white, it keeps direct sunlight off the original case.

Not that we get that much sun but it can be 3 C difference between covered/uncovered readings.

Hope this helps

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Phil - G0DOR

Thanks so much for those comments, and thanks for the link - good info. I want my data to be accurate as possible but that is so hard with one sensor. The aim is to create exposure to the air without taking heat of the air and that is why it worked for you. Mine does not receive sunlight on the sensor but heat from the north side of the house (southern hemisphere) and can't get wet so I have to have it at the house and has been within 10 metres of the greehouse because that is the only place I would get good wind measurements. A shield may work but it got a plastic cover and may still capture heat rising. I really feel that I should not make bad readings because my current project is fixing my bad readings so to get a website going. I don't want to make a decision between getting perfection of one and not the other. The question is whether day or night temps more important if I have to make that decision. Thanks for your reply Phil, it is greatly appreciated.

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Regards, Matt of Brisbane, Australia
Web Site: http://www.localweatherdata.0glo.com

Still working on getting my readings right. I have moved the sensor to the left edge of the west side patio wall, the side closest to the outside but because the daytime temps were higher than it should be (by about a degree) I tested using a basic shield and the daytime temps are correct without error. Amazing. But overnight temps are about a degree C too high so today I have moved it again slightly to the north side of the house closest to the patio to see if I can get good overnights temps but not high readings during the day. I think I getting there, and I think what happens tomorrow will determine whether I get good readings. Once I get this sorted (if I can- hope so) and resolve and edit out the bad readings with Cumulus then I will aim to get my website going.

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Regards, Matt of Brisbane, Australia
Web Site: http://www.localweatherdata.0glo.com

Any temperatue sensor placed against, or near, a wall of any type (brick, fibro sheeting, metal etc) is going to suffer from reflected, radiated and/or retained heat from that wall. This is why 'official' temperature sensors (electronic or mercury/liquid) are placed in a Stevenson Screen with minimum distances stipulated between the screen and any surrounding buildings and/or plants.

Basically you are going to have to acept that placing the sensor anywhere near a wall, no matter which way it faces, is going to give you some false and/or elevated readings. Putting buckets, plastic cups, newpapers or whatever over the sensor when it is near a wall isn't going to help you get true readings.

Bottom line - if you want highly accurate readings, be prepared to pay a LOT of money for accurate sensors (not the toys we are all using here because, let's face it, this is what they are) and place them in a properly constructed screen with designated minimum distances between the screen and its surroundings. If you can't do that - without being funny about it, accept what the sensor tells you. If necessary, put a statement to the effect that this is an amateur site and should be treated as such.

Stephen

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Punctuation is the difference between 'Let's eat, grandma' and 'Let's eat grandma'

Hello Matt.j5b,

As Stephen quote, placing the thermo-hygrometer sensor can be a nightmare in some environments, and at some point, you need to accept the fact of not totally accurate readings.

A work around will build a Stevenson Screen like this one http://sandaysoft.com/forum/viewtopic.php?p=40916#p40916, this thread also covers this point. http://sandaysoft.com/forum/viewtopic.php?f=16&t=5447

Good Luck.

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Marco-Luis
YV1HX
Cabimas, Zulia, Venezuela
http://www.twitter.com/meteoven

Thanks both of you for your comments. I do understand it is a problem with getting accurate readings on a wall, but I have to work with what my situation allows in terms of mounting the sensor in that I am limited to the location of the sensors. This is because the better side of the house would be the south side of the house but because of a neighbour with a taller house and many tree next to the house I think that would have a great effect on my wind readings for the worst, which I don't want to do. Also the temp sensor is weather resistant but not waterproof so I am keen at keeping at the house wall.

The sensors themselves are accurate it is just where they are located that makes the problem. I know that the offical practice is out in the open in the screen but for me that something I don't want to do, I do have space that is why my rain readings that I have been doing for many years are correct. The problem is not heat during the day. Before I used the shield it was reading too high by about a degree C but with the shield it is now spot on.

It is the location which is slightly protected that creates high overnight temps because it is not exposed as it should be for overnight temps. I am moving the sensor more and more closer to the north side so as long as I don't get daytime temps reading too high I might be able to get overnight temps correct. Then once I tried everything then I will have to be happy with the recordings. But thanks for the comments.

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Regards, Matt of Brisbane, Australia
Web Site: http://www.localweatherdata.0glo.com

Matt - I am going to presume you are in a brick/brick veneer building? Even sheeting or cladding? Either way your high overnight temperatures will be due to heat soak in the walls during the day which is being released overnight - thus the higher readings.

Being in Brisbane (or that area) your sensor should be on the south side of the house - any other side simply won;t give you anywhere near true reading. The north side - well you understand about that; east it will get the morning sun, west the evening sun.

As I mentioned before if you can't place the sensor in a screen then just use a spot and leave it. OK so the temperatures aren't accurate to 0.1C - but I guarantee the sensor isn;t that accurate either (despite what the manufacturers say).

I had similar situations - my temperature sensor is now on the south side (well it has been since 2000), wind vane located on top of the antenna pole on the north (the clearest location I could find but is still affected by attenuation from surrounding bush and houses) and ther rain gauge on top of the garage opn the north side. IOW - I just picked the best spots available knowing that temperatures WILL be affected by the wall of the house at times (this shows particularly around late Jan/early Feb during our hottest periods); the wind vane will be affected by local conditions and the rain gauge has its best possible location given the bush etc.

If you don't, at some stage say 'I've got the best spot I can' you are going to be forever chasing your tail. Remember - as said before - unless you are an official BOM station, it is an amateur weather station. (no offence meant btw)

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Punctuation is the difference between 'Let's eat, grandma' and 'Let's eat grandma'

Kind of you to share your thought so thank you. I am in a low set brick house and I fully understand the sun path and the more sun on north side etc etc ... When it started more detailed records than just the weather and rainfall with a manual gauge in April 2009 I read about the seasons and all that sort of thing. About the heat soaking over night, the north side received sun during the day but less towards the top of the wall as the sun is higher at this time of the year and inside get much warmer during the day, but I did not think that it is the heat from the day. Before I moved it yesterday I had it on the west wall with a garage to the west of this west wall with a patio in between where it was more protected but too protected for overnight temps.

I know the south side is the best side but the cable from the temp hum sensor is only 10 metres so the sensors need to be same area so it is impossible to have wind readings on the north side because that is the best spot and move the temp sensor to the south side because the cable would not reach. Or if I moved the wind and rain sensors to the south side and it may end making it worst and to that would affect Cumulus because the batteries would have to come out and cause more trouble. And then I would have to move it back, that effort it not worth it. I am more interested in weather records without it stopping because all the sensor are moved to the other side of the house. The movement of the temp sensor I have been doing have only been minor movements.

I not just moving the sensor just for the fun of it, I am doing it to get to the closest to being correct and a screen is the most effective method but I can't do that. Is it all right that day time are correct and overnight is about a degree C too high. What is more important overnight or daytime temps, if it gets to a point I have to choose.

I know it is not a bom offical station and not trying make it one because my standards are different. For example my rain gauge is located on the east side on a fence 1 m off the ground about 3 to 5 metres from the back of the house with a large tree on either side of the gauge a few metres away. On the east there is a low tree from a neighbour next to us but is down lives further down. According to bom this is not right because it should be twice this distance but is quite open and I get good results.

I can be sure that I not going just keep chasing my tail, I am getting to the end of the project and once I done my best I will settle for that.

Your comments have been very helpful and your comments have not been offensive. Thanks

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Regards, Matt of Brisbane, Australia
Web Site: http://www.localweatherdata.0glo.com

Matt,

You could ring the Brisbane BOM office and talk to one of their INformation Officers (thnk they still call them that - they used to when I was there). They are (usually) very helpful and can guide you with some really good informaiton and tips.

Couple of things from what you say.

As long as your 'incorrect' readings are consistently wrong (bad choice of words, I know) then the reality is it shouldn;t matter. If they were wrong one way one day, and then wrong theother way the next - that would be a problem - but if they consistently read, say, 1.5 C higher than a manual thermometer - then let it be. Rememebr - you are recording a measurement for THAT location only - not one 10 metres or 1 km away. As long as they remain consistently 'wrong' you will have accurate records for THAT locaiton. If this makes sense?

Rain gauge - have to say you really should think about moving it. The trees will have a dual effect - one is shadowing - so if say, one tree is SE of the gauge and no the day of rain the wind is blowing from the SE, so is the rain, and you are more than likely to be missing rain coming from that direciton because the tree is shading the gauge.

The other side of this coin is, again, depening on wind direction and tree overhang, you are very likely to get rain drops coming off the leaves of the tree and not true rain.

There is nothing to stop you putting your rain gauge on the roof of your house - provided you don't have trees overhanging the roof line I have a flat topped carport/garage, and have put my gauge on the top of the front of it - it lies in line with the gutter on both my and the neighbours house and clear of anything higher than it by about 10 meres on either side (to the N and S are the roof peaks and nothing for over 50 metres to the E and W).

Have to say - from your description it would be rainfall I would be worrying more about being wrong than temperature. Drop me a PM if I can help/assist - but seriously - don't get too pedantic over locaitons unless the readings are so wildly incorrect. Try ringing the Bureau - you might be surprised how they can help.

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Punctuation is the difference between 'Let's eat, grandma' and 'Let's eat grandma'