Vernier scale facts for kids
A Vernier scale is a way to get a much better result when measuring how long something is or the size of an angle.
Sometimes when measuring things we need to get our measurement as accurate as possible. Accuracy is important in surveying the land, navigation of ships, making parts for machines like car engines, looking at stars and planets in astronomy and when doing experiments in science.
The working of Vernier scale
Length has been measured with a straight ruler for hundreds of years. If the object we are measuring is somewhere in between two of the marks on our ruler then we would have to estimate where between the two marks to take the measurement. A Vernier scale on our ruler does this last fine piece of measuring between the two marks for us. So, for example if the measurement with our eye said it was between 1.5 and When measuring angles the same problem occurs and a vernier may be part of a device to measure fine angles in between two of the marks on the scale.
We don't need to be sharp eyed to read the Vernier scale because its marks are almost as big as our main measuring scale. We just count how many marks there are to the next place where there is a mark on both the main and vernier scales that are exactly lined up. That number of marks tells us the size of the small extra measurement.
Images for kids

Mechanical displacement gauges with vernier scales on wall cracks (Moika Palace, Saint Petersburg).

When the jaws are closed and if the reading is 0.10mm, the zero error is referred to as +0.10mm. The method to use a vernier scale or caliper with zero error is to use the formula 'actual reading = main scale + vernier scale − (zero error)' thus the actual reading is 19.00 + 0.54 − (0.10) = 19.44 mm

When the jaws are closed and if the reading is −0.08mm, the zero error is referred to as +0.08 mm. The method to use a vernier scale or caliper with zero error is to use the formula 'actual reading = main scale + vernier scale + (zero error)' thus the actual reading is 19.00 + 0.36 + (+0.08) = 19.44 mm

A closeup of a caliper's measurement scales. Assuming the caliper has no "zero error" (that is, it registers 0.00 mm when fully closed) the image shows a reading of 3.58 mm ± 0.02 mm. This is found by adding 3.00 mm (left red mark) read off from the fixed main (upper) scale to 0.58 mm (right red mark) obtained from the sliding vernier (lower) scale. The main scale reading is determined by the rightmost tick on the main scale that is to the left of the zero tick on the vernier scale. The vernier reading is found by locating the closest aligned lines between the two scales. The 0.02 mm inscription indicates the caliper's precision and is just the width that corresponds to the smallest interval on the vernier scale.