Measuring the pressure

Being a nerd and having something of a scientific background, it should be no surprise to find that I quite like measuring instruments. But in any case, I always reckon every house deserves a barometer. Yes, we have one.

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It’s a very ordinary barometer. I might have liked a classy and truly accurate one like a Fortins but having to pay for that 76 centimetre column of mercury and then to have the stuff in a family home never seemed like a really good idea. So I settled for a plain aneroid barometer which we purched second hand from a shop in Wem in Shropshire.

At the heart of one of these barometers is a small corrugated metal box with the air sucked out (aneroid means without air). The air pressure on the outside is trying to crush the box but a spring of some kind prevents that from happening. Small changes in air pressure alter the shape of the box and a series of links and levers enlarges the tiny movement into something we can see as the needle moves on the dial.

The thinner, pointer can be set by hand so that you can see if the main pointer has risen or fallen. A falling needle might indicate that worse weather is approaching whereas a rising one can mean just the opposite. Oh, oh! The needle has fallen here so there could be worse weather later in the day.

So simple, so useful and so clever! I love it.

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