Temperatures

Hey buddy, what temperature is it anyway?.......

Thermometers, Thermostats, Thermo scopes ...

First let's define a thermometer:

WEBSTER'S DICTIONARY: Thermometer: An instrument for determining temperature consisting typically of a glass bulb attached to a fine tube of glass with a numbered scale and containing a liquid (as mercury or colored alcohol) that is sealed in and rises and falls with changes of temperature.

ANOTHER: Thermometer: An instrument that measures the temperature of a system in a quantitative way. How hot is the oven? How cold is it outside?

DIFFERENT DEVICE: Thermostat: A thermometer that uses its temperature measurements *to control* other equipment. Set the oven to maintain 350 degrees. I want the air conditioner to keep the house at 72 degrees. This is NOT the topic of discussion - simply offered for clarification.

Some of the earliest devices used to measure temperature (thermometers) were called thermo scopes. They were simple devices consisting of a glass bulb with a long tube extending downward into a container of colored water that was open to the atmosphere. Galileo, in 1610, is rumored to have used wine - good choice! As the air in the bulb was heated or cooled, the level of the liquid in the tube would rise or fall reflecting the change in the air temperature. By marking the side of the tube, a quantitative guide to temperatures was achieved.

Next came the "spirit" thermometers. In 1641, the first use of a sealed alcohol-in-glass device, with (temperature) marks on its stem was the beginning for our modern thermometer. This method was developed for Ferdinand II, Grand Duke of Tuscany.

Were you aware that Anders Celsius (1701-1744) - you know ... Celsius - actually used the reverse scale (as we know it today) where 100 represented the freezing point and zero the boiling point of water?

A year after his death, in 1745, Carolus Linnaeus of Upsula, Sweden, turned things on their heads. He designed a scale in which the freezing point of water was zero, and the boiling point 100.

For the mathematicians:
To convert from Celsius to Fahrenheit:
multiply by 1.8 and add 32. ° F = 1.8° C + 32

The early bulb thermometers relied upon the principal that liquids change volume relative to temperature. These liquids, water, alcohol, mercury rise and fall when subjected to heat and cold.

In order to gain a better handle on temperatures, along came the bimetallic strip thermometer. The use of metal rather than liquids has proven to be a much better gauge of measuring actual temperatures.

The bimetal thermometer uses the relationship of different types of metals expanding at different rates as they warm and cool. These metals are most often copper and iron. (Copper has the greater expansion coefficient and thus will expand more when heated and contract more when cooled.) These two different metals are bonded together in sandwich like fashion and can withstand fairly high temperatures. Consequently, these are often found in ovens.

Continued on Page 2 - Factory Installed Thermometers

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