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I am looking to purchase some new Vernier calipers, but I am overwhelmed by the amount of specs which are being offered. I need help in understanding how to evaluate them.

I do not want a dial or digital set of calipers, but rather am interested in any additional qualities such as the accuracy that these may offer which Vernier calipers can not.

Accuracy is the most important quality that I am looking for. For the sake of the question, assume that I have budget around US $2,000. What aspects of the Vernier calipers should I be looking at in order to have a high degree of accuracy? What else should I be examining with the calipers as part of this purchase?

I have some specific sub-questions that I haven't been able to figure out.

Graduation

A common amount is 0.02 mm, does this mean we can advance each measurement by a minimum of 0.02 mm? Therefore cannot get any closer a measurement from any 1 point on the scale?

Parallax-Free

I have read somewhere online that parallax-free aids the readability of calipers, thus allowing for less human error - If this is true, does this parallax-free attribute come at a cost? Do we lose some accuracy? (I think I read parallax-free Vernier calipers do not have a separate upper movable ruler like some of the others.)

Metric

I'm having a hard time identifying what's standard. What are common units offered?

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  • $\begingroup$ Why do you not want a digital? What is the problem you are trying to solve? What do you expect other than that a purchased COTS item meets the accuracy and precision quoted in the sales literature? $\endgroup$ – Carl Witthoft Dec 14 '15 at 15:37
  • $\begingroup$ Do you specifically want calipers, or just a way to make measurements? For a budget of $2,000 you could get a respectable micrometer set which would give you much more accuracy, if that matters to you. They do take more time to use though. $\endgroup$ – Ethan48 Mar 1 '16 at 14:11
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If your budget is correct at US $2000, you have very limited choice. You'll either have to opt for a 1000+ mm long caliper, or an antique one, probably used by da Vinci himself. The most expensive Mitutoyo vernier caliper they sell of the standard 150 mm length is less than UK £200. The accuracy is quoted at +/- 0.05 mm. I'm not sure if you can go better with a vernier. 0.02 is common with dial calipers.

Your specifications and focus on accuracy seem at odds with my experience. If accuracy is primary, then go digital (to 0.01 mm for £500). They're easier to use, zero out, and do relative measurements. They use batteries of course.

As to metric/Imperial, you get both but metric is more common in Europe whilst Imperial is more common in the Colonies. I don't think that you can have both on the same instrument like a rule. Digital can though. If you're one of those people who do engineering in 'ths, then there exist fractional display digital calipers that can read for example, 1 3/16th inches.

Also please do not confuse accuracy with precision. Precision, like resolution, is the degree of repeatability of readings. You can easily have a very accurate 0.05 mm dial caliper that is better than a crappy 0.01 mm digital one from the DIY store.

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  • $\begingroup$ There are non-digital calipers with metric and imperial scales: $\endgroup$ – Jim S. Dec 15 '15 at 14:00
  • $\begingroup$ @JimS. Verniers? $\endgroup$ – Paul Uszak Dec 15 '15 at 14:22
  • $\begingroup$ A dial caliper. Here is mine. Since the statement was made that digital might be the only option for dual units, I thought I would mention a non-digital alternative. $\endgroup$ – Jim S. Dec 15 '15 at 18:31
  • $\begingroup$ @PaulUszak Could you provide a link for 0.01mm accuracy digital calipers? $\endgroup$ – RobertBarington Dec 15 '15 at 22:31
  • $\begingroup$ @RobertBarington mitutoyo.co.uk/small-tool-instruments-and-data-management/…. It's waterproof which seems overkill, but it's the only one listed as having 0.01mm guaranteed accuracy. Mitutoyo are regarded as some of the best. You might have to consider thermal characteristics at this level of precision. Good job Christmas is coming eh? $\endgroup$ – Paul Uszak Dec 15 '15 at 22:55
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If you are looking for smaller Least Count, it would come at the cost of overall length i.e. the least measurable dimension getting smaller, the span of the instrument would also decrease.

Graduation is the size of the indicator, the line markings on the scale and not the measurable quantity.

Vernier Callipers with both the units, centimetre and inches in one instrument are available.

Parallax error is a human error and to lessen the effect some opticals aids may be provided.

A digital Vernier Callipers would solve your problem as the result would be displayed and hence the graduation and the parallax errors are removed. Also facility of changing units is also available in digital Vernier Callipers. So instead of looking for a Vernier Callipers with better Graduations, reduced Parallax error and specific units, a digital Vernier Callipers would be more handy.

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