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Thermometers - Information and a UK Buyer's Guide

Thermometers @ Amazon
- Check out the digital ear thermometers (eg the Braun High Speed Thermoscan), the Grobag Egg (for room temperature), clinical digital thermometers, nursery and bath thermometers, dummy thermometers and no touch forehead thermometers.

galileo thermometersThe Galileo Thermometer

Galileo thermometers were originally one of the first types of thermometer ever invented - they were invented by Galileo Galilei in 1593. are available in a range of sizes (see adjacent photo). They consist of an enclosed glass vessel that contains water, in which are suspended weights. These weights are themselves sealed glass containers containing different coloured liquids, and the temperature they represent hangs beneath.

weightAs the temperature changes, the density of the liquid changes and the weights rise or fall to reach the position where the density within them is equal to that of their surroundings. The current room temperature is given by the disc attached to the lowest weight in the upper part of the thermometer. In the picture to the left, the weight is displaying a temperature of 20°C.

Galileo thermometers are available in a range of sizes and make an attractive conversation piece. They can be bought online from Otherland Toys in the UK.

The Alcohol and Mercury Thermometers

The alcohol thermometer was invented by a German, Daniel Gabriel Fahrenheit in 1709, and he followed this by inventing the mercury thermometer in 1714. These types of thermometer consist of a sealed glass tube with a bulb of liquid at one end (either mercury or alcohol) and a scale up the side of the tube. When the temperature rises, the liquid expands and the top of the liquid reaches further up the tube, where the current temperature can be read.

LCD and Digital Thermometers

These are the most modern thermometers in use today. The LCD versions are typically flat and change colour to the show the temperature within a limited range. They are ideal for sticking onto the side of aquariums, for example.

The digital versions measure temperature quickly and accurately, and give the temperature as a read out on an LCD screen. They need batteries to operate.

Fahrenheit and Celcius

In 1724, Daniel Gabriel Fahrenheit introduced the Fahrenheit scale for measuring temperature. However, later in the eighteenth century, in 1742, a Swede, Anders Celsius, invented a scale for measuring temperature where the point 0°C is the freezing point of water, and the 100°C point is the boiling point of water. There are therefore 100 degrees between the freezing and boiling points of water. The Celcius scale is also known as the centigrade scale.


The Kelvin scale was invented by Lord William Thomson Kelvin in 1848. This scales follows the Celcius scale linearly, but zero on the Kelvin scale is absolute zero - the theoretical lowest temperature possible. This is given as -273.15°C. Although this temperature is theoretically impossible to reach, in practice temperatures very close to this have been measured. At absolute zero, molecules have no energy or movement - this changes the properties of certain materials, eg some metals lose their resistance and become become superconductors.


Thermometers Direct
- Thermometers for all requirements, including food and fridge thermometers; infra red, digital, room and shop thermometers; oven, bath, heating, air conditioning, plumbing and garden thermometers; together with a range of pond and aquarium thermometers. Also LCD thermometers that can be stuck on eg to a fish tank or a wine bin.