General knowledge for digital calipers
In the last 20 years , the digital caliper come into the market. It
can be easier to use due to the latest designs.However, it is more
expensive than the old ones. Another useful features of the digital
calipers are that they can be easily switched between inch and
metric units on the readout, tolerance indications, digital output
to electronic data collection systems, zero setting anywhere along
the caliper's range and retention of the zero setting even when the
caliper is turned off. With no moving parts in the readout, the
digital caliper is exceptionally durable, standing up to some of the
toughest manufacturing environments.
It is very important that the digital calipers must be treated with
care and respect. Don not use it for purposes for which it was never
intended (such as prying things apart). Do remember to wipe it clean
after using, and do not throw it on the workbench.
Always check the caliper often for wear, as well as burrs and
scratches on the jaws and contacting surfaces. You can just pass a
master disc along the jaws while inspecting for wear or taper. It is
extremely vital that a caliper should be calibrated at least once a
year—more often when use is heavy or there are multiple users of the
same instrument.
Though the caliper is a versatile tool, it is not one of the most
precise. Skill is required for positioning the tool and interpreting
the measurement result. As the user develops his "feel"
for the tool, his measurement results become more consistent.
Moreover, it also requires skill to apply the tool properly to the
dimension being measured. The jaws of the caliper must be square or
perpendicular to the part. They are held firmly against the part,
but not to the point of deflecting them. The part should be kept as
close as possible to the frame of the measurement tool.
The rule of ten says that a measurement tool should have ten times
more resolution than the tolerance of the dimension. Calipers
typically read in 0.001-inch units. So if the tolerance is tighter
than ±0.005 inch, a micrometer (or some other higher accuracy tool)
is the way to go.