Anyone plz explain the calibration procedure for Vernier caliper???
One of the best instruments for measuring the inner and outer dimensions of an object is called a Vernier Caliper. It is a very useful tool that has an L-shaped frame with a scale on the inner side and an L-shape sliding attachment with a vernier. The tool measures an object’s dimension by measuring the distance between two of its shorter arm edges (inner/outer). Vernier Caliper is named after its inventor Pierre Vernier in 1631 and it is an extremely accurate piece of measuring instrument.
When using any measuring equipment one of the most important things to remember is its accuracy. These kinds of instruments can lose their accuracy and precision over time. Due to atmospheric conditions or incorrect human handling any equipment can decrease its performance and accuracy. To stay on the safe side it is recommended to perform professional calibration services every 6 – 12 months.
CALIBRATION PROCEDURE. Place the standard Length of 25 mm between the measuring jaws of the caliper at three different positions and determine the length. Determine the average length and record the observations. Repeat the above procedure for the remaining standard lengths (50 mm, 75 mm, 100 mm, and 125mm). A Vernier Caliper should be calibrated in accordance with the ISO/IEC 17025:2017 international standard (ISO 17025 Vernier Caliper calibration) or the British National Standard (traceable Vernier Caliper calibration).
Detailed procedure of calibration:
1 First and foremost, the caliper’s jaws which are the parts responsible for measuring distances should be cleaned to make sure they are free of any dirt or grease.
2 The gear should be moved back and forth to make sure that it is moving without any hindrance.
3 Next comes to the zero reading check. Bring the jaws in contact with each other and check the reading on the dial. It should be zero. If this is not the case then set it manually to zero.
4 Insert a 0.500-inch (12.7 mm) standard gauge block between the jaws used to measure outer diameters. Both the jaws should be in contact with the block but do not press the jaws too tightly on the surface. Record the reading accurately to 3 decimal places. Take at least three readings to eliminate any inconsistency while measuring.
5 Step 4 should be repeated with a 1- inch (25.4 mm) gauge block and afterward with a 4-inch (101.6 mm) block. Note the readings.
6 The same procedure may be carried out using micrometer standards as well which are 0.150, 0.200, or 0.300 inches. Record and compare these readings as before.
7 To calibrate the internal jaws, set them to 0.500 inches (12.7 mm) and use the locking screw to fix their position. Then use another calibrated vernier caliper to measure the distance between the jaws. Record the readings and compare. Take multiple readings for more accuracy.
8 Repeat step 7 setting the jaw position at 25.4 mm and 101.6 mm sequentially. Observe and record the readings.
9 Now to calibrate the height measurement, set a 12.7 mm gauge block on a flat surface. Place the caliper vertically so that its bottom flat surface rests on top of the gauge block. Now extend the depth measuring stick using the thumb screw so that it touches the ground and note the reading.
10 Repeat step 9 using the 25.4 mm and 101.6 mm gauge blocks. Similarly use the micrometer standards to obtain another set of readings.
It is recommended that Vernier Caliper Calibration should be performed at least once every 12 months. The use and treatment of the instrument significantly impact its accuracy, so extensively used items may need more regular calibration.