Monitoring Temperature in a Greenhouse

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beesrus

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Re: Monitoring Temperature in a Greenhouse
« Reply #15 on: February 05, 2015, 19:43 »
Although ... :)
I have found that there is a lag between the falling outside temperature and the inside one, so inside perhaps minimum temperature is only help for an hour whereas outside it might be 2 or 3 hours, so the plants are only subjected to minimum cold for a brief period before temperature climbs when the sun rises.heats up, so the lag, at night, is even greater, so on a cold frosty night at the point when minimum outside temperature is reached it is still falling rapidly, rather than having bottomed out, and then starts climbing as the sun comes up; the inside temperature is falling too, but with considerable lag, which means its usually several degrees warmer than outside, and it starts warming with sunrise at the same time as outside does :)
:D Actually Kristen, I agree with your lag theory. We are a pair of theorists.  :)
With that lag in mind, and if my early cusp Spring days are not too fully booked, I make sure that my visits to the greenhouse are early morning, rather than at dusk. That way, any end of day stored heat in the greenhouse is not wasted by my opening of the door. Early morning visits are de rigeur.

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Headgardener22

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Re: Monitoring Temperature in a Greenhouse
« Reply #16 on: February 22, 2015, 17:55 »
My experiment  proved nothing  :(.

I put a max/min thermometer inside a black waterbutt which was stood in the polytunnel in the sun for over a week. The difference between max and min was one degree, regardless of the fact that the temperature in the polytunnel ranged between -2C and 25C and it was sunny for some of the time.

Time to think of something else.

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Kristen

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Re: Monitoring Temperature in a Greenhouse
« Reply #17 on: February 23, 2015, 13:52 »
That's a good idea - particularly as it turned out that water did not heat up much. I've been trying to think of how to measure the temperature of water with one of my temperature loggers, which are not waterproof ... :D

A 1C rise on 1 cu.m. of water is a bit more than 1kWh, which is probably enough to heat a 12' x 10' greenhouse overnight at this time of year (i.e. I'm thinking that a 2kW fan heat on for 30 minutes, total, for the night would keep a greenhouse at 10C ish?)

I've got my loggers measuring inside temperature of a 4-shelf blowaway, zipped up in my Greenhouse, another in the greenhouse, and a third outside, to see what the lag / heat-store value of the blowaway is, if any.  Going to be a few more days before I have enough data to publish.

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adri123

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Re: Monitoring Temperature in a Greenhouse
« Reply #18 on: February 23, 2015, 15:52 »
Where do you buy the logging thermometers? Had a search and can't find them.

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cadalot

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Re: Monitoring Temperature in a Greenhouse
« Reply #19 on: February 23, 2015, 17:13 »
Lidl sell them at around £3 from time to time, they are supposed to be for cars and have an inside and outside reading and save the max and min, so you reset to zero each day.
Digital Thermometer.jpg

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Kristen

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Re: Monitoring Temperature in a Greenhouse
« Reply #20 on: February 24, 2015, 00:20 »
Where do you buy the logging thermometers? Had a search and can't find them.


http://www.rapidonline.com/test-measurement/voltcraft-dl-101t-usb-temperature-data-logger-51-5408

Sometimes on offer at Clas Ohlson, Conrad and probably Maplin/

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cadalot

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Re: Monitoring Temperature in a Greenhouse
« Reply #21 on: February 24, 2015, 06:27 »
A quick search on ebay using "Temperature Data Logger" and these are half the price of the one above and one comes with a probe that could be used for soil temperature
Data Logger.jpg
Data Logger 2.jpg
« Last Edit: February 24, 2015, 06:32 by cadalot »

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Markw

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Re: Monitoring Temperature in a Greenhouse
« Reply #22 on: February 24, 2015, 08:15 »
Cadalot
I am not very far away from you. I use Tinytag Talk 2 data loggers, I would be only to happy to pop over and set some loggers up and get you some information.
I have used them loads of times, I have even buried them in the soil to record soil temperature. so it is easy to record outside, inside, and soil temperature you can then download all the data and print all the information in graft form
http://www.geminidataloggers.com/software
« Last Edit: February 24, 2015, 08:24 by Markw »
“When a well-packaged web of lies has been sold gradually to the masses over generations, the truth will seem utterly preposterous and its speaker a raving lunatic.”

Dresden James

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cadalot

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Re: Monitoring Temperature in a Greenhouse
« Reply #23 on: February 24, 2015, 09:16 »
Hi Markw
Thank you for the offer but I have just purchased a couple of data loggers (the one in the post above with the probe) and some additional cheap small max min temperature & Hygrometer gauges at £3 picture below that run on a single AAA battery

What were your findings when you set them up in your greenhouse?

I have found that now I have installed reflective panels in the top of the space saver greenhouse there is a significant difference from one side of the greenhouse to the other, and top to bottom
Digital LCD Thermometer Hygrometer Horticulture Temprature Temp Humidity Weather.jpg
« Last Edit: February 24, 2015, 09:20 by cadalot »

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Markw

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Re: Monitoring Temperature in a Greenhouse
« Reply #24 on: February 24, 2015, 11:43 »
Hi Cadalot
I think they are a must have bit of equipment. Not just for the greenhouse but for other monitoring situations.
I have quite a few of them some with probes. they work in the range from -40c to +125c .
They can be set to take a reeding every second or even up to once a day
I have used them in fridges and freezers to see if they are working correctly. in the house for balancing rads etc.
For growing the ones with the probe can be used for soil temperature so you can set up your propagator correctly. In a greenhouse they can be for setting your heating at night time or on a cold day. in the summer you can use them for cooling  if you have an opener installed.
If you were using say 4 of them you can overlay the data on one graph this makes it easy to see what is going on. I have used them for nearly 10 years now and I would be lost without them now. If you were using them for setting up your house heating they pay for them self very quickly.
I have some saved charts somewhere I could send you if you like.
« Last Edit: February 24, 2015, 11:47 by Markw »

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cadalot

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Re: Monitoring Temperature in a Greenhouse
« Reply #25 on: February 24, 2015, 13:48 »
Hi Cadalot
I have some saved charts somewhere I could send you if you like.

Yes please I will PM you with my email address

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adri123

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Re: Monitoring Temperature in a Greenhouse
« Reply #26 on: February 24, 2015, 21:22 »
I've toyed with the idea of buying one of these to see what's going on...but now realise that all I need to know is it's blooming freezing and nothing's going to grow.

If there's any merit in them it's just the fun of seeing what's going on temp wise.  Is that wrong?

Adri

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cadalot

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Re: Monitoring Temperature in a Greenhouse
« Reply #27 on: February 24, 2015, 21:53 »
What has amazed me is that there is a recordable lag with between levels of enclosure reaching the same temperature but that also appears to work in reverse in the morning when heating up. By taking off the propagators lids the temperature equalised more quickly.

And yes when not heating a greenhouse over night, it isn't an awful lot of use for bringing most seeds on early, than when in full sun over the last week the temperatures in side rocket to 40C and then drop as the sun goes behind shielding buildings.

based on these extremes of heating, it's a wonder anything grows and stays alive. But isn't nature a wonderful thing?     

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adri123

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Re: Monitoring Temperature in a Greenhouse
« Reply #28 on: February 24, 2015, 21:59 »
Did I write 'blooming' freezing?

Don't think so.

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cadalot

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Re: Monitoring Temperature in a Greenhouse
« Reply #29 on: February 25, 2015, 07:08 »
Did I write 'blooming' freezing?

Don't think so.

Tis the power of Aunty she is everywhere and see everything, plus some word are pre programed to alter on the forum especially around Christmas time  :lol: :D :nowink:



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