Digital Vernier

Gentlemen,
ALDI's are selling Digital Verniers for £8.99 in a case with a spare battery, I've just bought one to put with my Van tools. It also has a very
large digital display for us old un's
Martin P
--
snipped-for-privacy@btopenworld.com

Semper in Excrementem Altitudo Solus Varius
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You can also find 100/150/200 mm length digital readouts that can be screwed to a slide . Makes a nice pseudo CNC type action if you get what I mean- advertised on EBAY about £20.
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message

<pedant>
"Vernier" is a type of scale - see http://en.wikipedia.org/wiki/Vernier_scale . I think you mean "Digital Calipers".
</pedant>
http://www.aldi.co.uk/uk/html/offers/2867_6564.htm for more info.
--
MatSav



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MatSav wrote:

<pedant>
Iirc, digital calipers use the same mathematical principle as a vernier scale.
</pedant>
-- Peter Fairbrother
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Ok something to measure with a digital display, some of us appear to have nothing else better to do :-))
Martin P

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Not any of the fairly large number of DROs, LVDTs and sundry gadgets I've worked on over the years, including the freaky Sony one that was a tube stacked with accurately sized balls.
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Andy Dingley wrote:

The Sony one sounds interesting.
Ordinary digital calipers have about 14-17 staggered rows of 4-6 metal strips on the circuit board, which combine with other metallisations in the plastic strip on the frame to form capacitors when they are in close proximity.
The spacing of the strips on the circuit board and in the plastic strip is such that there a small movement causes the capacitors formed to change, which is converted to a reading.
The spacing of the two plates is like the spacing on a vernier scale, in that it's not a whole number, and that fractional/vernier type spacing is what gives the scales their resolution.
It's a bit more complex than that, as instead of using just one point they use 7-10, but the principle is the same.
-- Peter Fairbrother
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Peter Fairbrother wrote:

Newall uses the same principle, I think.
Balls inna tube.
Cheers Trevor Jones
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wrote:

Sounds like something the Spanish Inquisition thought up <G>
Peter
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It's Newall's patent, so if Sony are using the technique, they must be doing so under license from Newall or have circumvented the patent as an Aussie chap has done.
Mark Rand RTFM
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Correction to that:- The patent has now expired.
How is it that Harry Webb feels that he should still be paid for work he did in the '50s, but manufacturers' work can be copied after a couple of decades?
Mar Rand RTFM
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I wish that Harry Web had patented his 1950s work. By just doing cheap copyright he's still got it and us poor souls are still being given it. I still wish he would just 'Move it' Alan
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What has Cliff Richard got to do with digital calipers?
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Trevor Jones wrote:

How does it work? Does it count the number of balls which pass a sensor, or do they act as parts of capacitors?
Best wishes,
Chris
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Ah, I see what you mean. Yes, I guess this would have to count as a vernier. It's a variant on the old "translucent ruler with a diagonal line" technique.
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Andy Dingley wrote:

I just took one apart.
I think it's just a simple vernier spacing rather than a diagonal, the diagonal arrangement is just to fit the pads in, as they would be too wide if they were in a single line.
There are 72 pads on the board, which is ~ 42 mm long. The pads on the bottom are 2.7 mm apart, so the 72 top pads cover 15 bottom pads, giving a resolution of 72x15 = 1,080 in 2.7 mm (that's the vernier bit), or 400 per mm.
This would be downgraded to 100 per mm for the metric readout, or converted to inches.
I have seen one before which is slightly different though, the pads were about 5 mm apart. I was surprised this time, thought they would all be the same.
-- Peter Fairbrother
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Peter Fairbrother wrote:

That's perhaps a bit misleading, it's not a simple vernier. Think of it as doing 15 verniers simultaneously, each vernier having 72 possible values, with a slight displacement between each.
The scale then finds where the values of the 15 verniers change, giving another 15 x the resolution. It's kind of a double vernier.
I hope that's clear, I know what's happening but I find it very hard to explain!
-- Peter Fairbrother
or 400

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http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item60045965213&ssPageName ­ME:B:DBS:GB:1123
this is one......
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