Jumping Barograph

[ponapay]

My barograph trace jumps every day at about 1730. It seems to leap about 6 mbs and then steadies down until the next day. It always increases.

I have tried to determine whether the drum is slowly climbing during the day and then dropping or whether it is the pen. My felling is that it is the pen.

I thought, at first, it might be some supersonic aircraft passing but have not heard any shockwaves.

Any ideas.

ps It is a very old barograph.

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[boatless]

Dent or lump in the drum? Drum bearings shot?

Do you slam the front door when you get in from work?



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[A_7]

Central heating coming on? Evening sun warms room and/or barograph?

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[ponapay]

Thanks Boatless & A_7

Have tried all those and can't see any corelation.

Will check further on bearings, but the drum has the clockwork motor inside it and the drum is fixed in height and the gear wheels do not appear to have any appreciable wear or lack of verticality in the cut.

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