Day 249~366

Yay now Autumn has arrived we’re having summer!Β πŸ™„ with nice warm days predicted by the BBC weather lady. I beg to differ πŸ™‚

Aneroid barometers have a sealed, air-tight metal box inside. As air pressure rises or falls, the box either squashes inward a tiny bit or flexes outward. A spring is cunningly attached to the box and, as the box moves in and out in response to the changes in air pressure, the spring expands or contracts and moves the pointer on the dial. The dial is calibrated (marked with numbers) so you can read the air pressure instantly. Aneroid barometers measure the air pressure when you knock their glass faces. When you first inspect them, the needle shows the pressure as it was when you last looked at themβ€”however long ago that might have been. Give the glass a sharp tap and the needle will jump to a new position showing the pressure as it is now. The way the needle moves is important. If it moves clockwise, up the dial, the pressure is increasing so the weather is likely to be getting hotter, drier, and finer; if the needle turns counterclockwise, the pressure is decreasing and the weather is likely to get cooler, wetter, and poorer.
There are lots of different units you can use for measuring pressure, in the old days it was ‘Atmospheres’,’Torrs’,& ‘millibars’, though these days pascals and kilopascals are the preferred scientific units to use.

I just read what the needle points at.



21 thoughts on “Day 249~366

  1. When I was young we often stayed on my uncle’s farm. In the dark old farmhouse there hung a barometer on the wall. I always asked my father how it worked. I don’t think he knew – all he ever replied was – “I don’t think that thing works anymore”. Maybe he did not know about the tapping thing?!

    Liked by 1 person

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