Day 175
June 24, 2010‘Phew! what a scorcher‘ is the typical headline when we have had a couple of days sunshine.
Add this to the inevitable declaration of a drought, which has now occurred in the North West of England and Summer is well under way!
Our Galileo Thermometer is working overtime…..
Suspended in the liquid are a number of weights. Commonly those weights are themselves attached to sealed glass bulbs containing colored liquid for an attractive effect. As the liquid in the cylinder changes temperature its density changes, and the bulbs are free to move, rising or falling to reach a position where their density is either equal to that of the surrounding liquid or where they are brought to a halt by other bulbs. If the bulbs differ in density by a very small amount and are ordered such that the least dense is at the top and most dense at the bottom, they can form a temperature scale..
The temperature is typically read from an engraved metal disc on each bulb. Usually a gap separates the top bulbs from the bottom bulbs and then the temperature would be between the tag readings on either side of the gap. If a bulb is free-floating in the gap, then its tag reading would be closest to the ambient temperature.
To achieve satisfactory accuracy, the weights are required to be manufactured to a tolerance of less than 1/1000 of a gram (1 milligram).