Vernier calipers are measuring tools used mainly for measuring linear dimensions. These calipers come handy in measuring the diameter of circular objects. Their circular jaws fit securely on either side of the circumference of round objects. Vernier calipers have two types of scales- a fixed main scale and a moving Vernier scale. The main scale is normally in millimetres or 1/10th of an inch. Vernier calipers score well over standard rulers because they can measure precise readings up to 0.001 inches. Vernier scales is used along with the Vernier calliper for accurate measurements.
Range of Vernier Calipers:
The maximum capacity of a Vernier caliper is the difference between the smallest and largest measurement reading. Usually, it is the total length of the main scale. Vernier calipers, generally, have a range of 300 mm. Vernier calipers of smaller ranges are also widely available in the marketplace.
Vernier reading is the smallest measurable distance captured by a Vernier caliper. It is also termed as "Resolution" of the Vernier caliper. Imperial Vernier calipers have a resolution of 0.001 inches. The resolution of metric Vernier calipers varies from 0.02mm to 0.05mm. The resolution is normally indicated at the end of the Vernier scale.
Tolerance or instrument error refers to accuracy of Vernier caliper readings. Vernier calipers are generally used for low tolerance measurement readings. Low tolerance measurement readings are accurate and reliable because there is a minimal chance of error. The tolerance of Vernier calipers is +- 0.03mm (+- 0.0015 in). Calipers with quadri feature are used to take step measurements.
Dial Calipers and Vernier Calipers:
The readings displayed on dial calipers are easier to read, but some people do find it easier to read Vernier caliper readings. Both dial, as well as Vernier calipers, provide readings with the same accuracy.
Using the Vernier Caliper:
a)Familiarize yourself with the part of vernier caliper: The primary jaws of the vernier caliper are used for measuring the external diameter. The smaller jaws are meant for measuring the internal diameter of the objects.
b) The Vernier Scale Reading: A caliper has a main scale and sliding (Vernier) scale. Usually, a vernier scale has an engraved label depicting the value it represents.
c) Unlocking the Screw: Some vernier caliper models have locking screws. Make sure you unlock those screws before you start using the vernier caliper. Twist the screw counter-clockwise to unlock it.