How to read a vernier
To read a vernier scale to 1/50
mm or 0.020 mm, the vernier scale must have 49 mm divided
into 50 equal spaces for use with 1.0 mm graduations on the
true (or main) scale (
click here to see our example of verniers in a pop up
window) or go to the
example page and print it out for your reference.
First, look at the
metric example.
The vernier "0" is between 30.4 cm (304mm) and 30.5 cm
(305mm). To determine the precise location, count across
the vernier from "0" to see which line exactly coincides
with a line on the true (or main) scale. It is the 33rd
line. Therefore, the correct reading to 1/50mm is 304.00mm
+ 33 x .02mm = 304.66 mm (or 30.466 cm).
Likewise, for the inch vernier, to read to 0.001", one must
have 50 graduations on the vernier over 49 spaces of 1/20"
(or 0.05") graduations on the true (or main) scale (1/50 x
1/20 = .001").
Now, look at the inch example. "0" on the vernier is
between 12.000" and 12.050" on the true scale. Count from
"0" to the first line that coincides exactly with a line on
the true (or main) scale which is the 8th. Therefore, the
correct reading is 12.000" + 8 x 0.001" = 12.008".
Other combinations of main scale graduations and vernier
graduations are possible for both inch and metric reading
for these or other resolutions. For example, for 1/10 mm
(0.1mm) resolution, one needs only 10 graduations on the
vernier over 9 (1mm) graduations on the main scale (1/10 x 1
= 0.1mm resolution, etc...
For angular verniers, the same principle applies. For 1/10º
(0.1º), one may have the main or true scale divided into 360
x 1° increments; and the vernier divided into 10 graduations
over 9° of the main scale. The reading is the same as for
linear scales.
Likewise, angular verniers can be
used to accurately read degrees, minutes or military units.
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