A Vernier caliper is a measuring instrument used to obtain precise measurements of length, width, and depth of an object. It consists of two main parts: the main scale and the Vernier scale. Let's understand how it works and how it provides precise measurements:
Main Scale: The main scale is a graduated scale that runs along the length of the caliper. It is typically engraved on the fixed part of the caliper. The length of the main scale can vary, but it is usually 150mm or 6 inches.
Vernier Scale: The Vernier scale is a secondary scale that slides along the main scale. It is located on the movable jaw of the caliper. The Vernier scale is slightly shorter than the main scale and has its own set of graduations. These graduations are spaced more closely than those on the main scale.
Jaws and Depth Rod: The Vernier caliper has two sets of jaws - the main jaws and the smaller jaws on the movable Vernier scale. These are used to measure external and internal dimensions of objects, respectively. Additionally, there is a depth rod attached to the movable jaw to measure the depth of holes or recesses.
Here's how the Vernier caliper works to provide precise measurements:
Taking an External Measurement (Length or Width):
Open the jaws by sliding the Vernier scale along the main scale to create a gap slightly larger than the object's length or width.
Place the object between the jaws, ensuring it is held securely without any gaps.
Close the jaws by sliding the Vernier scale until it makes contact with one end of the object.
Read the main scale value that aligns with the zero mark of the Vernier scale (the zero mark of Vernier scale is usually not aligned with the zero mark of the main scale).
Find the Vernier scale graduation line that lines up best with any graduation line on the main scale. This is the Vernier scale reading.
Add the main scale reading and the Vernier scale reading to get the precise measurement of the object's length or width.
Taking an Internal Measurement (Depth):
Use the depth rod to measure the depth of a hole or recess by inserting it into the hole and making sure it is perpendicular to the object's surface.
Read the depth measurement directly from the main scale, where the depth rod's tip is located.
The Vernier scale allows for a finer measurement resolution than what can be achieved using the main scale alone. By aligning the Vernier scale with the main scale, it helps to eliminate parallax error (an apparent shift in the measurement due to the viewer's perspective) and allows for highly precise measurements to be taken.
With practice and attention to detail, the Vernier caliper can provide accurate measurements with an error of about 0.02 mm (0.001 inches) or even better, depending on the quality of the caliper.