How to use the vernier calipers ?
�?The Vernier calipers are high precise measuring instrument; the
reading error is 1/20 mm = 0.05 mm.
�?Close the jaws lightly on the object to be measured.
�?If you are measuring something with a round cross section, make
sure that the axis of the object is perpendicular to the caliper.
This is necessary to ensure that you are measuring the full diameter
and not merely a chord.
�?Ignore the top scale, which is calibrated in inches.
�?Use the bottom scale, which is in metric units.
�?Notice that there is a fixed scale and a sliding scale.
�?The boldface numbers on the fixed scale are centimeters.
�?The tick marks on the fixed scale between the boldface numbers are
millimeters.
�?There are ten tick marks on the sliding scale. The left-most tick
mark on the sliding scale will let you read from the fixed scale the
number of whole millimeters that the jaws are opened.
�?For example, if the leftmost tick mark on the sliding scale is
between 21 mm and 22 mm, so the number of whole millimeters is 21.
�?Next we find the tenths of millimeters. Notice that the ten tick
marks on the sliding scale are the same width as nine ticks marks on
the fixed scale. This means that at most one of the tick marks on
the sliding scale will align with a tick mark on the fixed scale;
the others will miss.
�?The number of the aligned tick mark on the sliding scale tells you
the number of tenths of millimeters. In the example above, the 3rd
tick mark on the sliding scale is in coincidence with the one above
it, so the caliper reading is (21.30 ± 0.05) mm.
�?If two adjacent tick marks on the sliding scale look equally
aligned with their counterparts on the fixed scale, then the reading
is half way between the two marks. In the example above, if the 3rd
and 4th tick marks on the sliding scale looked to be equally
aligned, then the reading would be (21.35 ± 0.05) mm.
�?On those rare occasions when the reading just happens to be a
"nice" number like 2 cm, don't forget to include the zero
decimal places showing the precision of the measurement and the
reading error. So not 2 cm, but rather (2.000 ± 0.005) cm or (20.00
± 0.05) mm.