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Thermometers:
Thermometer Timeline
Who invented the thermometer?
The first recorded thermometer was produced by the Italian, Santorio
Santorio (1561-1636) who was one of a group of Venetian scientists
working at the end of the Sixteenth Century. As with many inventions
the thermometer came about through the work of many scientists and
was improved upon by many others.
1596
Galileo Galilei and the first thermoscope
Galileo Galilei is often claimed to be the inventor of the thermometer.
However the instrument he invented could not strictly be called
a thermometer: to be a thermometer an instrument must measure temperature
differences; Galileo's instrument did not do this, but merely indicated
temperature differences. His instrument should rightly be called
a thermoscope.
The Thermoscope
The predecessor to the thermometer, the thermoscope is a thermometer
without a scale; it indicates differences in temperature only ie
it can show if the temperature is higher, lower or the same, but
unlike a thermometer it cannot measure the difference nor can the
result be recorded for future reference. The thermoscope was widely
used by a group of scientists in Venice that included Galileo. It
was only a small step from the thermoscope to the thermometer.
1612
Santorio Santorio - the first thermometer
The Italian, Santorio Santorio (1561-1636) is generally credited
with having applied a scale to an air thermoscope at least as early
as 1612 and thus is thought to be the inventor of the thermometer
as a temperature measuring device. Santorio's instrument was an
air thermometer. Its accuracy was poor as the effects of varying
air pressure on the thermometer were not understood at that time.
1654
The first sealed liquid-in-glass thermometer
The sealed liquid-in-glass thermometer, more familiar to us today,
was first produced in 1654 by the Grand Duke of Tuscany, Ferdinand
II (1610-1670). His thermometer had an alcohol filling. Although
this was a significant development his thermometer was inaccurate
and there was no standardised scale in use.
1714
The first mercury thermometer
Gabriel Fahrenheit (1686-1736) was the first person to make a thermometer
using mercury. The more predictable expansion of mercury combined
with improved glassworking techniques led to a much more accurate
thermometer.
Fahrenheit - the first Standard Thermometer Scale
Fahrenheit used the newly discovered fixed points to devise the
first standard temperature scale for his thermometer. Fahrenheit
divided the freezing and boiling points of water into 180 degrees.
32 was chosen as the the figure for the lower fixed point as this
produced a scale that would not fall below zero even when measuring
the lowest possible temperatures that he could produce in his laboratory
- a mixture of ice, salt and water. It is sometimes suggested that
Fahrenheit divided his scale into 100 degrees using blood temperature
(incorrectly measured) and the freezing point of water as fixed
points - this is not true. The Fahrenheit scale is still in use
today.
1731
The Réamur Scale
In 1731 the Frenchman, René Antoine Ferchauld de Réamur
(1683-1757) proposed a thermometer scale on which the freezing point
of water was 0° and the boiling point was 80°. The Réamur
scale is not in use today.
1742
The Celsius Scale
In 1742 a Swedish scientist named Anders Celsius (1701-1744) devised
a thermometer scale dividing the freezing and boiling points of
water into 100 degrees. Celsius chose 0 degrees for the boiling
point of water, and 100 degrees for the freezing point. A year later,
the Frenchman Jean Pierre Cristin (1683-1755) inverted the Celsius
scale to produce the Centigrade scale used today (freezing point
0°, boiling point 100°). By international agreement in 1948
Cristin's adapted scale became known as Celsius and is still in
use today.
1848
The Absolute Temperature Scale or Kelvin Scale
In 1848 Sir William Thomson, Baron Kelvin of Largs, Lord Kelvin
of Scotland (1824 - 1907) proposed the absolute temperature scale
with zero degrees being the theoretical lowest temperature possible
where molecular motion ceases. Kelvin defined 1 Kelvin degree as
being equal to one Celsius degree. The Degree Kelvin is the current
Standard Unit of temperature measurement.
Other information on wireless thermometers:
How to use wireless thermometers
Where to buy wireless thermometers
Features to look for in wireless thermometers
Thermometer timeline
Facts about wireless thermometers
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