In order to measure the length of a small rod, we follow the following steps:

- Find the least count and zero error of the vernier callipers.
- The rod is placed between the fixed end and the vernier scale as shown in the diagram.
- Note the main scale reading.
- Note that division p on the vernier scale which coincide or is in line with any division of the main scale. Multiply this vernier division p with the least count. This is the vernier scale reading i.e., Vernier scale reading = p x L.C.
- Repeat it two times and record the observation.

**Observations —**

Total number of divisions on vernier scale (n) = ………..

Value of one division on the main scale (x) = ……….. cm

$Least count (L.C.)=nx =……….cm$

Zero error = ……. cm

S No. | The main scale reading a (in cm) | Vernier division coinciding (p) | Vernier scale division b = p x L.C.(in cm) | Observed length = a + b (in cm) |
---|---|---|---|---|

(1) | ||||

(2) | ||||

(3) |

Mean observed length = ……… cm

From the mean observed length, subtract zero error, if any, with its proper sign to obtain the true measurement of the length of the given project.

Thus we get,

**Observed length = main scale reading + (vernier division p coinciding with any division on the main scale) x least count.**

**True length = observed length – zero error (with sign).**