Precautions While using of vernier caliper & Few Possible errors

In order to minimum the error the following precautions should be taken while using the instrument.

1. First of all these should not be treated or used as a wrench or hammer because these are not rugged instruments.
2. They must be wiped free from grit, chips and oil. These should be brought to the workpiece.


3. The line of measurement must coincide with line of scale.
4. While measuring the outside diameter with vernier caliper the plane of the measuring tips of the calipers must be perpendicular to the center line of the work piece. The caliper should not be fitted/twisted.
5. The instrument is gripped near to the jaws.
6. The caliper jaws are moved on the work with light touch under
7. pressure should not be applied.
8. The accuracy of measurement depends on sense of sight & sense of
9. feel.
10. If play exists then the gib at the back of jaw assembly must be bent so that gib holds the jaw against the frame and play is removed.
11. The measuring instrument must be properly balanced in hand and held lightly in such a way that only fingers handle the moving and adjustable screws.
12. The lower jaws should be opened slightly and their inner surface should be cleaned and dried with a cloth gently. This should be repeated with the upper jaws as well.
13. Loosen the locking key of the vernier caliper and make sure there is no friction between the scales while moving the jaws of the vernier caliper.
14. While using digital vernier bring the jaws in contact with each other and then press the on/off button. Check the reading and make sure it is zero.
15. In the case of a digital vernier caliper move the slider and check whether all the buttons and the LCD display are working properly.

Here are the Few Possible errors occurs while using vernier instruments :-
The various causes of errors are given in the following.

1. No play should be there between the sliding jaw on scale, otherwise the accuracy of the vernier caliper will be lost. 
2. The main reason for causing error that While gripping the object to be measured, application of excessive force on the jaws should be avoided. The excessive force leads to show error .The object should always be gripped gently between the jaws. This is extremely important while measuring objects which are easily deformable e.g wires.
3.  If the sliding jaw frame becomes worm or warped it will not slide squarely on the main scale and will cause error in measurement.
4.  Due to wear and warping of the jaws the zero line on main scale may not conclude with that on the vernier scale. This is called as zero error.
5.  Errors are also caused by incorrect reading of vernier scale as the scales are difficult to read even with the aid of magnifying glass.



6. Error is also introduced if the line of measurement does not coincide with the line of the scale.
7. Since it to difficult to obtain correct feel due to its size and weight an error may be introduced due to incorrect feel.