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Vernier Calipers is a measuring device used to measure small length up to two decimal places.

**:**

__It has two scales__**i)
**Main scale
like ruler (in cm). This gives measure of length in one decimal place.

**ii)
**ii) Vernier
scale'(having ten division). This gives value of second decimal place.

** Diagram**:

Vernier Callipers |

__Least__**It is the least distance which can be measured accurately by it is also called Vernier constant.**

__count__:If 10 div of main scale = 9 div of Vernier scale
then

Least count of Vernier Callipers will be 0.01 cm** **

__Zero__**If zero of Vernier scale not coinciding with zero of main scale, said to have zero error.**

__error__:

__Types of errors__**:**

** **1. Positive zero error- When zero of Vernier scale
right side of zero of main scale.

2 Negative zero error- When zero of Vernier scale left side of zero of main scale.

Zero error = __+__ n x L.C,
where n is the division of Vernier coinciding with the any main scale division.

__Calculation__**: **

Length = M.S.R + V.S.D X L.C

True Length= Length- zero error with proper sign

(Where M.S.R - main scale reading,

V.S.D- Vernier scale division coinciding with main scale and L.C - least count)

**:**

__Learn to measure__

** **__Question__**:
**The least count of a vernier
callipers is 0.01 cm and its zero error is

- 0.03 cm. While measuring the length of a
rod, the zero of vernier scale lies between 5.3 cm and 5.4 cm and sixth
division on vernier is in line with a marking on the main scale. Calculate the
length of the rod.

** **__Solution__**:
**Length of the rod MSR + VSD x LC
= 5.3 cm + 6 × 0.01 cm = 5.36 cm

True length of the rod = observed reading - zero
error = 5.36 cm - (-0.03 cm) = 5.39 cm.** **

__Measuring devices__:** **