Among
the tools that are used for measurement of length, a precise instrument as
mentioned earlier is the Vernier Caliper. It can measure upto a precision of
0.1 mm or in other words 0.01 cm. The latest ones can even go upto 0.05mm!
Parts with purpose:
How to take a reading through an
error free Vernier Caliper:
Take that reading on the Main Scale (the
large, stationary scale, like your ruler). It is noted on the metric side (cm,
mm) as that value which is just before the zero mark on the vernier scale.
Hence MSR in this example is 3.2 cm
Step 2 : Note the Fractional Part (Vernier Scale Reading VSR):
Note VS division VSD which is that division
on the Vernier Scale which co-insides with any division on the main scale. In
the following example, the sixth division is coinsiding with some division on
MS.
VSR =
VSD x L.C
where VSR: Vernier Scale Reading, VSD: Vernier
scale division, and LC: Least Count (which is 0.01 cm for most vernier calipers
that we study).
Least Count:
The Least count of a measuring
device is the least distance ( resolution / accuracy ) that can be
measured using the device.
Formula:
LC = (Value of 1 Main Scale Division) / (Total number of vernier scale
divisions)
Hence LC for Vernier caliper = [1mm / 10 divisions]
= 0.1 mm = 0.01 cm
In this figure VSR = 6 x 0.01 cm = 0.06 cm
Step 3: Total Reading Observed: MSR + VSR
3.2 cm +
0.06 cm = 3.26 cm
Examples
In the following figure MSR can be seen as 2.3cm where as
VSR = VSD x L.C = 5x0.01cm = 0.05cm. Hence total observed reading gets to be:
2.3+ 0.05 cm = 2.35cm
Further Examples
Now lets view examples with more advanced precision . You
will realize that whether we work it one way or the other,
our answer gets to be the same.Notice:
Hence, whether you take the reading on the vernier division (42) and multiply it simply by 0.01 or you adapt the method of counting the small lines (21) and multipying by the precision often mentioned on the latest verniers (0.02) ; in both cases your Vernier Scale Reading will come out to be the same (0.42mm)
