How a Hygrometer works

Studying weather instruments:

We have been looking at weather instruments in the school weather station. Remember the white louvred case is called a Stevenson screen. Inside the weather station we looked at the instruments and what they do, and what they are called.  

There was a rain gauge, a maximum-minimum thermometer, a dial thermometer,  a barometer, and a hygrometer.  We looked at how they measure each of the weather elements they record.  Now my donkeys have helpfully demonstrated how a hygrometer works.


So that my donkeys know what the weather is going to be like, and can go in the stable when it looks as if it might rain, I have installed a small weather station called a “banjo barometer”.  You can see it behind Matilde: it is the green object on a corner post of the stable.  You can see why it is called a “banjo” because it looks like the musical instrument. These contain a therometer, a barometer (the large dial) and a hygrometer (the small dial).

barometerchewed weather station

One of the donkeys decided to eat the hygrometer today, but I do not know which naughty donkey did it.  The evidence is the teeth marks on the green wooden banjo, and the missing hygrometer.  The transparent plastic case was gone, but the metal inside of the hygrometer had been chewed up and spat out on the floor.


Rubí usually eats nearest to the weather station, but she is probably not to blame.  It is Aitana who always explores anything new that arrives on the field and tests it to see if it is edible.

Donkeys demonstrate hygrometer

Aitana exploring a brush to see if it is edible.

This was all a bit disappointing until, suddenly I realized what the donkeys were really trying to do: they wanted to show Year 7 pupils how a hygrometer works!  Now we can pass the donkey-chewed hygrometer around the class and see how it works!

This type of hygrometer is a Mechanical hygrometer and its metal coil is tightened or loosened by the presence of moisture, turning the needle to show humidity.


Thank you donkeys for demonstrating how a hygrometer works.  Thanks also to Elians science teachers for helping to explore the physics of the instrument.