Zero Setting
It is extremely vital to check the zero setting after checking the
caliper jaws for wear. This process is obvious: close the jaws and
check if the vernier reads 0.000. Then, you can adjust to zero by
loosening the adjusting screws, and repositioning the adjusting
screws, and repositioning. For reliable measurement, this process
might not provide the best solution. If most of your measurements
are in the 75 to 130 mm (3 to 5in.) range, for example, you should
zero at the 100mm (4 in.) point—the approximate center of where
the majority of your measurements on a standard of known size
(true value) such as a gage block.
Here, we have summarized some information about vernier calipers,
but without making any allowance for good or bad manipulation. We
will include a table like this one for each important instrument,
because the table will help you select the best instrument for the
job, whether in the physics laboratory or in the shop floor.