Precautionary Steps While Taking Measurements By Vernier Caliper

Often during experiments or in the industry there is a very small margin of error. Some of that error is due to the environmental conditions or inherent in the procedure which we cannot control. The other part is due to human error and errors in the system. These errors lie within our control and can be eliminated if the proper measures are taken otherwise the measurements can be significantly inaccurate which is obviously undesirable.

These precautions are necessary to minimize any errors which can affect the accuracy of the measurement. In this article we will list a few important things which should be considered while using a vernier caliper for measurement.

# The most common form of error associated with measuring instruments is the parallax error. Parallax is a term which originates from the Greek word “parallaxis” which means “alteration”. Parallax error occurs when an object is observed from an angle. This makes the object appear at a slightly different position than it really is and can lead us to take a wrong reading on a measuring scale. To eliminate this error the observer should position his eyes directly above the scale when taking the Main Scale reading and the Vernier Coincidence.

# Care should be taken that all readings taken during the measurement are in the same unit system. E.g MKS system which uses the units metre, kilogram and second for measurement of length, weight and time. Another frequently used system is the CGS system which uses the units of centimeter, gram and second. If any measurements are taken in a unit in another system it should be converted to the appropriate units before being used in any calculations.

# While gripping the object to be measured, application of excessive force on the jaws should be avoided. The object should always be gripped gently between the jaws. This is extremely important while measuring objects which are easily deformable e.g wires.

# Before taking any measurements, make sure the vernier caliper does not have a zero error. This can be checked by bringing the jaws of the caliper in contact with each other. The zero markings on the vernier scale and the main scale should align at this point. If not then there is a zero error and the appropriate corrections should be applied.

# The surface of the object which needs to be measured should be cleaned and dried with a cloth soaked in cleaning oil.

# The same should be done with the instrument cover.

# 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.

# 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.

In the case of a digital vernier caliper the following additional steps should be taken:

• Bring the jaws in contact with each other and then press the on/off button. Check the reading and make sure it is zero.
• Move the slider and check whether all the buttons and the LCD display are working properly.