Vernier calipers are used to measure in very exact amounts. Generally, they are used to read measurements within .001 of an inch. Digital calipers are easier and quicker to read than dial calipers and usually more accurate if used correctly.
Slide the rear jaw of the caliper so that it is closed against the set, front jaw. The caliper will slide without using the thumb wheel, when making larger movements. The thumb wheel is for fine adjustment.
Put some pressure on the thumb wheel to ensure that the caliper is fully closed. Press the "on" or "reset" button. This will zero the caliper and should be done before each measurement to verify accuracy.
Push the "in/mm" button. This button selects if you will be measuring in inches or in millimetres.
Rotate the thumb wheel to open the caliper jaws large enough to encompass whatever you are measuring. Hold the front jaw against the object.
Rotate the thumb wheel until the jaws are touching each side of the object. The measurement will be displayed in the digital window.
Change batteries frequently. Weak batteries can result in inaccurate readings. Vernier calipers also have a thin bar which extends from the rear of the caliper when the movable jaw is adjusted. This can be used as a depth gauge for measuring.
Do not put too much pressure on the thumb wheel when measuring. This will cause the jaw to give a little and cause an inaccurate reading.