does anyone know how to find absolute uncertainty of measuring equipment

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universalcj
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I though it is +- half of the Least Count and some of the chem books even say so
(e.g. burette 0.1ml => +- 0.05ml )

but I've just found that some physics past papers state that it is just +- the smallest division
(e.g. a meter rule : +- 0.1cm = +-1 mm )


additionally, would you guys mind writing down the absolute uncertainty of burette, a meter ruler, pipette and a vernier caliper ? thank you
Last edited by universalcj; 5 days ago
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TsRtSr1001
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This is probably something you can look up, it sounds like homework and whilst we can help you figure it out on here, we can’t just do your work for you. Try looking in the textbook, or if it’s not there, a revision sheet or simply any document. It also depends on the resolution of the equipment, as most of those items can have varying sizes.
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nzy
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In Physics, the smallest possible uncertainty of a measurement is still ± half of the resolution (or "least count") of the measuring instrument used.

However, some measuring instruments will actually require you to effectively take two measurements rather than one (or at least, this is the reasoning I've been taught). Take a standard metre ruler which you use to measure the length of the object - not only are you reading the value for the length given at the end of the object, but you're also lining up the opposite end with the 0m mark of the ruler yourself. As a result, you get two inherent sources of error, so the smallest possible uncertainty associated with a metre ruler is ± 2 x half of its resolution, ± 1mm. The same thing occurs with a stopwatch, and (I believe) a vernier caliper.

This is where Physics and Chemistry slightly differ, I think (or maybe not - I haven't touched much Chemistry since GCSE). I would argue that, for a burette reading, the smallest possible uncertainty would also be ± 2 x half of the resolution. Although you're not 'lining up' the liquid in a burette, to find the volume of liquid delivered, you're calculating the difference between the initial and final volumes. Both these readings each have an absolute uncertainty of ± half the resolution, which you would have to then add together if you subtract one volume from the other.
Last edited by nzy; 4 days ago
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universalcj
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(Original post by TsRtSr1001)
This is probably something you can look up, it sounds like homework and whilst we can help you figure it out on here, we can’t just do your work for you. Try looking in the textbook, or if it’s not there, a revision sheet or simply any document. It also depends on the resolution of the equipment, as most of those items can have varying sizes.
thank you for replying.... but this is not homework.... just a part of my revision for y13... and the reason why I posted here is every past papers , books and internet resources have shown different results....
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