CLOSING DOWN SALE Vernier (gem gauge) to measure your gems! An indispensable tool for gemstone fans!
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Product details
Gem gauge
to measure your gems!
This calibrated vernier is made of brass. It measures as small as a tenth of a milimetre. It measures in both milimetres and inches. It is indispensable for everyone who deals with gemstones, from jewellers to collectors to online buyers.
NB. Gem in photo is not included in the deal. Please see my gem ads and auctions!
Courtesy of Wikipedia ...
Why a vernier scale works
The vernier scale is constructed so that it is spaced at a constant fraction of the fixed main scale. So for a decimal measuring device each mark on the vernier would be spaced nine tenths of those on the main scale. If you put the two scales together with zero points aligned then the first mark on the vernier scale will be one tenth short of the first main scale mark, the second two tenths short and so on up to the ninth mark which would be misaligned by nine tenths. Only when a full ten marks have been counted would there be an alignment because the tenth mark would be ten tenths, that is a whole main scale unit, short and will therefore align with the ninth mark on the main scale.
Now if you move the vernier by a small amount, say, one tenth of its fixed main scale, the only pair of marks which come into alignment will be the first pair since these were the only ones originally misaligned by one tenth. If we had moved it 2 tenths then the second pair and only the second would be in alignment since these are the only ones which were originally misaligned by that amount. If we had moved it 5 tenths then the fifth pair and only the fifth would be in alignment. And so on for any movement, only one pair of marks will be in alignment and that pair will show what is the value of the small displacement.