I installed thermometers in two hives at the beginning of this year. I used units I found on ebay, they cost about 1 euro post included. There is a photo at:

http://www.flickr.com/photos/51242820@N08/5195884752/in/set-72157624281357330/


http://www.flickr.com/photos/51242820@N08/5196020712/in/set-72157624281357330/

I set the probe in the center of the nest between two frames. Some time later I saw that the bees had completely incorporated it into one of the frames. When they moved down into a second box the temperature fell so I installed a second probe by drilling a hole through the side of the box between 3 frames. I found it fascinating to follow the activity inside the hive by following the transfer of heat from one part to another. So far the temperature has not fallen below 27°C which is very reassuring.
Bil

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