Using a thermometer in the ground

[darc]

That's a good idea along the lines I was thinking but was not sure if
that would be affected by the air temp at ground level if the air could follow the wire down the tube.
A pic of the sensor just checked price and they are around the £40
mark so not a bad for the £1 I spent

[bruce45]

in the fact sheet the met office do state that only the 100cm thermometer is suspended in a tube and the others are direct in the soil. however, they can still be problems with heavy rain and water logged soil. I think it depends on how accurate you need your readings to be as to which way would work best in your situation.

[darc]

I would like it to be as accurate as possible, however the water table around us is always quiet high so I guess I would have to think on that as well I have read the fact sheets from the met office and as they use
better equipment I would like to get as close as I can with what I have
as we all do on the forum.

I still think what you said regarding a plastic type tube is about the
best I can do, I am glad you thought of the water logged ground bit
as at 300mm my probe will probably be swimming

[bruce45]

only to pleased to be of help as has already been stated guess work is not the answer and looking at all the factors about an issue with feedback from others can normally end up with the best solution.

I remember during the summer last year myself and a few others were testing the rg11 rain gauge with the help of Steve adding some new code. the results, despite many mods and options changes, are still very mixed so in that case there was a lot of guess work because there is no standard for this type of rain gauge.

one other option for you could be to put a soak away gravel pit below the probe to improve drainage in that area.

[darc]

Your right again I have wasted hours on guess work instead of listening to Forum Members at times getting it so wrong and as Steve has said
it does not help anybody on the forum if people just say things for sake of writing a few words on the forum, because people like myself who are only learning could take it as gospel and then get it all wrong and then get very disheartened, I no I do. Back to the subject I have strayed of a little I think a slight bit of drainage work below the sensor would work, I will have to talk nicely to my son see if he would dig me a whole as if I try and do I may end up dropping my w/chair into it.

Thanks again you have been most helpful.

Geoff

[bruce45]

you might need to check the location of services that could be under were you want to install the probe. a few years ago they put gas mains into the estate and we were told there would be following the footpaths. went on holiday and when we returned found they had a trenched thru the middle of the front lawn. was not amused as cut half the roots off a cherry tree which did not recover and had to be removed.

you could tell you son you buried a time capsule for him when he was born and to dig it up

[darc]

Ye will do, I will have to extend the cable on the prob before I do anything I am locating in close to all my other sensor's so just to
keep everything together. Will keep you posted of how it all comes together.

[bruce45]

could run into problems if you extend the cable to far. normally would have a thermistor which varies in resistance with temperature. so extending the cable would increase the resistance and cause wrong readings. you could extend the cable and then check it with a fixed known temperature so you no if it is reading high or low. it should be consistent over a temp range so as long as you can which way it is.

not really wanting to throw an other spanner into the works

[darc]

Yes I thought of that and will be checking at different stages before doing any soldering, Thanks

[darc]

Hi Bruce have now finally got the wire extended and then to overcome the problem with what you had said about extending cable I have extended the cable by about 3mtr then opened the thermometer housing and found a little adjusting screw and I have managed to
get the thermometer to an accuracy of about +/- 0.1 i think that is pretty good for a thermometer I only paid a £1 for and have extended the cable plus played around inside with but I in for a penny in for a £1
I have not put it in the ground yet I have got it sat between 3 thermometer's inc the Davis 1 so I can keep a close check on it.

Geoff PS just started snowing here.

[bruce45]

sounds like you have it sorted

[darc]

I hope so, my next stages are to get another 2 probes into the ground, 1 deeper and another shallower another on the lawn and 1 on the concrete I think then I will have a full house then except for a couple of sensors for my davis weather station that are a little out of my price range until I get back from Greece in may, then I will be allowed to spend again my wife has put a stop to my spending until then.

I have put the probe in the ground now at approx 30cm and it is reading 2 c I think that would be about right it's to dark now to do anymore outside so will check again 2moz with another thermometer.

Thanks for your help

[darc]

Good morning or goodnight depending on were you are on this little planet of ours, Checked the soil temp at 08.05 today and it was at 3c not sure how accurate that is but judging by my test yesterday it should be as close as +/- 0.1 it is chucking it down with rain here at the moment but I will stick another thermometer down to 30cm later and double check readings again, I hope it is ok.

Geoff