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Introduction:
A caliper is a device used to measure two
opposing sides of an object. This includes both
Internal opposing surface measurements or
external outlining areas. In its simplest form,
the tips of the calipers are held against the
points being measured, the calipers then removed
and held against a ruler to read the distance
between the two.
The Vernier Caliper, the Dial Caliper and
the Digital Caliper:
All these three types of calipers are just
differently designed devices which perform the
same function i.e. give a direct and highly
accurate readout of the distances being
measured. The said difference arises only in the
way the reading is measured.
Their Design Features:
- A calibrated scale with a fixed jaw. The main
or gross reading is recorded from this scale.
This has calibrations in metric measurements on
one side and in inches on the other edge. This
feature is the same for all the three types.
- A movable jaw with a pointer. This can slide
along the fixed scale. The position of this
pointer helps provide accuracy of reading. This
pointer is differently guided in the three
different types:
a. On a
Vernier Caliper, the position of the
pointer on a vernier scale gives the exact
readout. In practical use, this needs practice
and on workshop etc. This mechanism can be a bit
tedious to repeat throughout the day. These
provide a precision of up to 0.01mm
(10micrometres) or up to one-thousandth of an
inch, whichever unit may be applicable.
b. On a Dial Caliper, a small gear mechanism
drives the pointer on a circular dial instead of
on a scale. This pointer rotates every inch,
every tenth of an inch and then every
millimeter. This reading is then added to the
main scale reading to get the accurate
measurement.
c. The Digital Caliper, as the name implies,
features an electronic digital display in place
of the dial. On this, the reading is displayed
as a single value. Some models offer the option
of switching between the metric or inch systems.
One of the main advantages of the digital
caliper is its "reading hold " feature which
retains the readings recorded even in awkward
positions where the display may not be
immediately visible. These Digital calipers are
fabricated in Stainless Steel with a rated
accuracy of 0.02mm or 0.001inch. For a 6 inch or
150mm length caliper, with a reduction in the
accuracy values to 0.03mm or 0.001 inch for
100-200mm calipers and 0.04 mm or 0.0015 inches
for a 200-300mm caliper. Both the dial and
digital calipers allow a zero-setting feature to
allow differential measurements of distances.
- All these calipers have some form of a locking
device or holding mechanism to hold the jaws
without movement for accuracy of reading.
- Apart from this ,they have an innovatively
incorporated depth probe which can be inserted
into the finest of grooves for depth measurement
.
The digital caliper provides a serial data
output thereby facilitating interfacing with a
personal computer or a dedicated recorder using
a suitable device. Caution, the Digital calipers
continue to consume power even when they are
switched off, so prefer silver cells over
alkaline button cells. These devices find
extensive application in scientific
laboratories, Mechanical engineering workshops
,extensive industrial applications like machine
working, in manufacturing of guns, in Medicine,
in hand loading, woodworking and woodturning; in
short, anywhere where precise measurements are
imperative for the superior performance of the
end product.
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