Vernier caliper

You can drag the little brown wheel to adjust the calipers. This kind of calipers is meant for making internal, external and depth measurements.

Start by clicking a black link which configures the simulation for different demonstrations. Then check your observations with the blue "How", "Answer" or "Interpretation" links. After reading them, you can collapse them by clicking the link again:

Freely moveable, check zero! How: As for all measuring instruments, you should check the "zero" (= does it show zero when it should?). In this case it means: push the jaws completely together (with nothing in between). If everything is OK, the jaws will fit together so no light goes between them. (There are some "cutouts" near the base of the jaw which will NOT close. They have a special purpose we will cover below.) The narrow measuring tongue that usually sticks out the buttom should now be flush with the bottom. The furthest left gradation line on the short, vernier, scale should be directly opposite the zero line on the main scale. If this is not the case, the instrument must be adjusted or all subsequent measurements adjusted. This vernier caliper, despite it cheapness and rather coarse scale gradation, seems to be well zeroed. On digital calipers if they don't show zero when closed you press a zeroing button.

You can try to measure the round black circle. It is about 13,8 mm

You can collapse this text by clicking the How link again.!
Measure a complicated shape! : External diameter Answer: 25.3-25.4 mm Both line 3 and line 4 in the vernier scale match the main scale pretty well. The best answer would be 25.35 mm {with a certain risk for exaggerated impression of precision!}| Internal diameter Answer: 6.8 or 6.9 mm or 6.85 mm | Hole Depth Answer: 8.0 mm (7.9 mm isn't bad either) | Height: Answer: 13.6 mm
Now you could calculate the blue body's volume V = V_outer - V_inner = etc. = 6537,9 to 6600,6 mm³ or, better, rounded off to 6.5 to 6.6 cm³

A common mistake: Wrong placement Interpretation: Both circles have the same size. If you place something where the röd one is, it comes in the part that doesn't close when the scale reads zero. If you try to read the red circles diameter you get about 3.5 mm. The well placed green circle's diameter is read as about 4.8 mm. NOTE! Do not place things you want to measure in the cutout part of the jaws!
Why are there cutouts?: Without using cutout Interpretation: Sometimes one wants to measure the thickness of some sheet metal. If the edge has a folded edge or a deformations like in the picture, the parallell jaws will not be able to be pressed tightly again the sheet. One will get an overestmation of the thickness (which will include some air). Here one would get about 1.6 mm. Using cutout Answer: If we see to it that the "deformed" part of the sheet comes in the cutouts, then the jaws can close tightly on the sheet. Then we get the right thickness: 1.1 mm. (the previous value was almost +50% wrong)

A good animation of reading vernier scales

Extra: measuring fractional inches

If you like fractions you can try the "inch" scale on the top of the caliper. The smallest divison on the main inch scale is 1/16 inch. Each division on the vernier inch scale is then 1/128 inch! Good luck!

If you try an "Internal diameter" measurement with the inch scale: Hint 1 the Zero line of the inch vernier is just past 1/4" = 4/16" Hint 2 the third (or fourth) line, right of zero, on the vernier /128ths inch scale matches the main scale Hint 3 Using the third line we would get: 4/16 + 3/128 = (4*8)/(16*8) + 3/128 =
You can remove all the hints with (All) (All)
Answer:
(32+3)/128 = 35/128 " (or a tiny bit more, since the fourth line matched pretty well too).