So, Dan brought home some temperature probes from work. They are one time use boxes that come with a chemical that must be kept above freezing. So there is a chart inside that records the temperature during the trip. When it arrives, Dan cracks open the case to see if the temp dipped below freezing. If it has, they return the chemical.
One day a whole bunch of boxes arrived with the detectors but only one needed to be opened so Dan brought the rest home for the kids.
It runs on a battery.
Here's the coil which is a bi-metal strip (no I didn't know that, but E10 remembered and he just told me...see a good lesson!)
Dan heats up the bi-metal strip to show the kids how it will move. The strip has two metals in it and one wants to expand more than the other. Since it can't go anywhere like it normally does (being attached to the other metal) it puts more curl in the coil. This moves a plastic thing attached to the scratch paper and it makes marks. And that is how it records the temperature! Again, E10 just provided that review.
The kids put these boxes in a few places around the house- one went in the attic, one in the freezer and one in the frig. They opened them up to check out the readings.
The one in the middle shows you how they are all rolled up before you pull them to check on them. Click on the picture below and see if you can figure out which one is which!