Measuring objects and distances is one of the first things mankind came to require once we discovered the use of tools and started building things for ourselves. For most uses, measuring scales do the job pretty well and everyone knows how to use one. However the measuring scale only offers a certain degree of accuracy and once you require precise measurements which lie between two marks on the scale it becomes hard to get an accurate reading without a bit of rounding off. Also measuring scales are very prone to parallax errors which can cause a wide degree of variance in readings from person to person which is not good for applications such as scientific experiments, machining of tools or parts that require fine tolerances and navigation etc.
Vernier Calipers are tools which fulfill that much needed requirement. The vernier scale was invented in 1631 by French mathematician Pierre Vernier to enable measurements more precise measurements from a normal measuring scale. Calipers are measuring objects which can grip the object to be measured and provide a reading based on the movement of a measuring scale. The combination of both these things resulted in the birth of the Vernier Caliper, an invention so popular that it is still one of the most widely used tools.
A modern vernier caliper consists of two sets of jaws. The lower jaws are bigger and are used to measure normal solid objects or the outer diameters of hollow objects and holes etc. The upper jaws are there to measure the inner dimensions of objects. There is a fixed main scale which is graduated in millimetres or inches depending on whether the caliper is in metric or imperial units. The inches are further divided into tenths on the main scale. The main scale is complemented by a smaller, moving scale which is known as the vernier scale and gives the caliper its name. The vernier scale further divides the smallest increment on the main scale into further parts enabling measurements up to 0.01 mm or 0.001 inches.
The vernier scale is divided into either 20 or 50 parts on an imperial scale. This means that the smallest increment on the main scale i.e 1mm is divided into 50 or 20 divisions. This gives the least count of the caliper which is the smallest measurement that can be made using the caliper. This leads to a least count or resolution of 0.02 mm (1/50) or 0.05mm (1/20).
So what does a Vernier caliper measure? The simple answer is anything that can fit between its jaws! Usually vernier calipers are used to measure inner and outer diameters of rods and spheres and thickness of any kind of object. The vernier caliper can also be used to measure depths of holes and objects which can be very difficult to do with any other scale. This is done through the depth rod which is attached at the end of the vernier caliper.
There is no denying that vernier calipers have played a significant role in the rapid enhancement and improvement of technology, enabling much more precise engineering to be done than was previously possible.
With the onset of the digital age, vernier calipers have also evolved into digital calipers which rely on electronics to provide instant and even more precise readings. They also reduce the difficulty and learning curve associated with reading the vernier scale which requires a good eyesight. They can also provide readings in multiple units so that conversion is not needed.