2. Define:
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.
3. Precautions
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.
4. No 1
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.
5. No 2
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 meter, 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.
6. No 3
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.
7. No 4
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.
8. No 5
The surface of the object which needs to be measured
should be cleaned and dried with a cloth soaked in
cleaning oil.
9. No 6
The same should be done with the instrument cover.
10. No 7
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.
11. No 8
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.
12. 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.
13. While Taking Measurements there are
big chances of getting an error to
understand more about the
precautions
read this article.
