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3D3DThermostat switch.
This is a small self-contained thermal switch: It make an electrical contact when the temperature rises above 60C. It works by having two small wires embedded in what amounts to a simple mercury thermometer. When the column of mercury reaches the second wire, the connection is made. Why build a switch this way rather than use a bi-metallic strip such as is used in common household thermostats, or an electronic sensor? Well, it's much more accurate than the bi-metallic strip, and it was probably made before electronic sensors were practical. (And even now, it's much simpler and probably more reliable than an electronic system. I don't know if switches like this are still made or commonly used today.)
Source: eBay seller tubesrus
Contributor: Theodore Gray
Acquired: 16 July, 2006
Text Updated: 5 December, 2006
Price: Donated
Size: 2"
Purity: 99.9%