In a caliber we must take into account the measurement range, the amplitude that can be measured and the appreciation, which is the minimum measurement that can be appreciated by virtue of the division (precision) of the vernier scale.
We can see, as an example, some calibers to see these characteristics. As a reference we will take a range of measurements from 0 to 100 mm, and depending on the shape of the scale of the ruler and the vernier (or Vernier scale), different configurations of vernier calipers arise:
- With a vernier with 10 divisions of 9 mm in total length and with an appreciation of 0.1 mm, to be able to measure up to 100 mm the scale of the ruler must have an extension of at least 109 mm:.
(The "0" on the vernier scale coincides with a division of the ruler when the reading is a whole number of millimeters, just as it does with the division indicated by the number 10.)
- If that same caliper had the 10 divisions of the vernier in a length of 19 mm, it would have the same appreciation of 0.1 mm, but to a greater extent, requiring a ruler scale of at least 119 mm:.
- If the 10 divisions are distributed over a length of 29 mm, the scale of the ruler will have to have a length of 129 mm to be able to measure up to 100 mm with an appreciation of 0.1 mm:.
- With a 20-division vernier or vernier, the appreciation is 0.05 mm. If the vernier has a length of 19 mm, to be able to measure up to 100 mm the ruler must have a length of 119 mm:.
- If we extend the vernier with 20 divisions to 39 mm, it maintains the same appreciation of 0.05 mm, but the ruler has to measure 139 mm to be able to measure up to 100 mm:.
- A vernier of 40 divisions will give rise to an appreciation of 0.025 mm, and with a length of 39 mm you need the scale of the ruler to reach 139 mm to be able to measure 100 mm:.
- The vernier of 50 divisions has an appreciation of 0.020 mm; With a length of 49 mm, the ruler will have to measure 149 mm to be able to measure up to 100 mm:.
These are the most common configurations of a vernier caliper with a vernier or Vernier scale. It is not normally specified, since this form of vernier is considered the normal one, but it is usually called the n-1 scale, since the length of the scale is equal to n-1, with n being the number of divisions.
There is another form of vernier or vernier scale, not so common, which is called n+1 in which the length of the vernier scale is n+1, with n being its number of divisions.
In verniers or n+1 vernier scales the scale extends from right to left. To find the match indicated by the decimal part, start at the division on the right, indicated with the number 0.
We can see some examples of this type:
- In this example we have a vernier of 10 divisions (which, therefore, gives an appreciation of 0.1 mm) in a length of 11 mm to the left of the zero of measurement. To be able to measure up to 100 mm, the scale of the ruler must measure 111 mm, with 11 divisions to the left of zero:.
- A vernier of 10 divisions, with the same appreciation of 0.1 mm, and with a length of 21 mm to the left of the zero, needs a ruler, to measure up to 100, of 121 mm, with 21 mm to the left of the zero of measurement. This configuration, although it may seem strange, meets the same conditions as cases n-1:.
- Another example of a n+1 vernier or vernier scale on a caliper is one with 20 divisions, with an appreciation of 0.05 mm and a length of 21 mm to the left of zero, which requires a 121 mm ruler to measure up to 100 mm, with 21 mm to the left of zero:.
- If we extend these 20 divisions by 41 mm, we have the same appreciation of 0.05 mm, and the ruler will have to measure 141 mm to be able to measure up to 100 mm, with 41 mm to the left of zero:.
- An n+1 scale of 40 divisions has an appreciation of 0.025 mm and the vernier or vernier has a length of 41 mm. The ruler, in order to measure 100 mm, measures 141 mm in total and 41 mm to the left of the zero measurement:.
- With 50 divisions the appreciation is 0.020 mm, and with a length of 51 mm the ruler needs a length of 151 mm to be able to measure 100 mm; As in all cases n+1, the 51 mm are to the left of the measurement zero:.
The vernier or Vernier scales, whether they are n-1 or n+1, have similar characteristics: the assessment depends only on the number of divisions, with a different orientation of this scale with respect to the ruler.
The most common scales are n-1, especially in vernier calipers, but n+1 scales are not disposable.