What is A Vernier caliper & History behind its Invention? It is a special measuring device consisting of a fixed scale and a sliding Vernier scale on top of it, widely used to measure thicknesses and diameters of objects. The caliper contains two measuring jaws attached to these scales and an objects length is found by measuring the distance between them. Invented by French mathematician and inventor Pierre Vernier, the Vernier caliper delivers highly accurate readings due to an enhancement factor which is created because of a difference between the divisions on the Vernier scale and main scale.
Which measurements can be taken by this instrument? It can be used to measure inside and outside diameters plus the length of a step and depth of an object. To measure the outside diameter, place the object between the lower jaws and grip it firmly. Use the lock screw to fix the scales position and note the readings. The same steps apply for inside diameters but use the upper jaws instead. Steps can be measured using the head of the caliper and the right hand upper jaw. Place the sliding jaw on a steps edge and open the caliper till the right upper jaw touches the lower step and note the reading. The depth gauge lies at the end of the main beam. First rest the beam surface on the objects edge, then open the caliper till the depth gauge touches the bottom and then note the reading.
What Precautionary Steps to be taken when using this instrument? There are some important precautions to take while measuring objects with a vernier caliper to minimize errors. Position your eyes directly above the scale while measuring to reduce parallax error. Use consistent units to avoid calculation errors. Don’t grip the object so tightly as to cause deformation which changes the length of an object. Ensure there is no zero error by closing the jaws and noting the alignment of the zeros on the two scales. Use the on/off button in case of a digital caliper and check the LCD and all buttons to see if they are working. Lastly ensure all parts of the caliper are clean and moving smoothly.
Accuracy and precision are two important characteristics of any measuring instrument. Accuracy tells us how close the measurements are to the true value and is related to the systematic errors in an experiment while precision describes the reproducibility of a measurement and is linked to the random errors in a system. Random errors are caused by any variation while measuring. This includes parallax errors or instrument variation. Random errors can be eliminated by taking averages. Systematic errors are caused by an inaccuracy in the instrument or method and cannot be eliminated unless its source is identified and fixed. E.g. zero errors.
How to Calibrate Vernier Calipers? These as discussed are precise instruments so they need to be carefully calibrated to ensure their accuracy is preserved. This involves calibrating all the measuring surfaces including both sets of jaws and depth gauge using standard gauge blocks. To calibrate the outer jaws, first clean the jaws, check if they are sliding smoothly and check zero error. Then insert a 0.500 inch standard gauge between jaws and note the readings. Repeat the steps with 1 inch and 4 inch gauges. To calibrate internal jaws set them at 0.500, 1.00 and 4.00 inch and use another calibrated caliper to measure the distances respectively. Lastly place the 0.5 inch gauge on a flat surface and use the depth gauge to measure its height from the surface. Take averages to improve accuracy.
Common questions about this instruments are asked by students and beginners. You are recommended to go through our FAQs to know more about this instrument: