IMAGE. A Vernier scale. You should record 9.2 mm for the measurement shown.
A Vernier scale is an auxiliary sliding scale that can be used to more accurately read the values on a fixed main scale. Its purpose is to allow accurate readings, rather than estimations, between the smallest graduations on the fixed scale. A vernier scale commonly has ten graduation marks. Each division on the Vernier scale is nine-tenths of the size of the finest division on the main scale.
To use the Vernier scale, read the main scale to the last certain digit. The last certain digit on the main scale is the graduation just below the zero on the vernier scale. The mark on the vernier scale that directly lines up with a graduation mark on the main scale is the last digit in your reading.
