| Read your room temperature, from
the top surface of the coloured liquid in the single ball. The thermometer in the
picture shows a temperature of 28°C. If it gets warmer the ball will
sink lower but only far enough to indicate the correct temperature and no
further.
The Ketten is an fascinating way to
indicate your room temperature, to within a degree or so.
Available
with a green or a cognac ball.
This is a very clever thermometer! How
does it work?
Height: 32cm
| Model: |
KTC (Cognac) |
KTG (Green) |
| Price: |
£34.00
(£39.99
inc. p&p*) |
£34.00
(£39.99
inc. p&p*) |
|
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|
* Carriage paid to;
England, Wales, Scotland (incl. Highlands & Islands), N. Ireland, Isle
of Man & the Isles of Scilly ONLY.
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It works
like this - The Ketten and
Galileo thermometers both use the Archimedes buoyancy principle to
indicate temperature. How are they different?
When temperature increases, a ball in a Galileo thermometer will
eventually become too heavy for the liquid and it will sink all the way to
the bottom half of the thermometer. It sinks all the way to the
bottom because it remains too heavy to be supported by the liquid.
When temperature increases, the ball in a Ketten thermometer will
eventually become too heavy for the liquid and it will also sink.
However, part of the weight of the ball in the Ketten thermometer is the
two chains, attached to it's bottom. You can see that the chains are also
attached to the side walls of the thermometer itself.
Imagine that, if the ball was high enough, the chains from the ball to the sides of the
thermometer would be almost straight (like an upside-down V). In
this situation, the ball carries almost all of the weight of both chains. Now imagine that the bottom of the ball is level with the
ends of the chain on the thermometer side (the chain would look like a double U). In this
situation, the ball only carries half the weight of each chain as the
other half is carried by the side supports.
The rule is then that when the ball sinks, the weight of the chains that it carries gets less. So, when
the temperature rises and the ball begins to sink, the reduction in the
weight of the chain restores the balance and the ball stops sinking.
Similarly if the temperature drops and the ball rises, the increase in
weight of the chain prevents it continuing to rise. Very
Clever!
Two other items: (1) In Germany, 'Ketten' is
similar to Cable and (2) these
thermometer are sometimes referred to as 'weight-loss' thermometers, for
obvious reasons!
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