Caliper, Ruler, Set-Square

Various measuring tools have been created to make accurate measurements, and representations, of spatial objects; in this section, we look at three key types.

Calipers

Caliper(s) are an instrument used to measure the length, width, thickness, diameter or depth of an object or hole. Many types of calipers permit reading out a measurement on a ruled scale, a dial, or an electronic digital display. A common association is to calipers using a sliding vernier scale. 

Figure 1: Different kinds of Caliper

Rulers

Rulers are graduated scales drawn onto a straight stick or edge. A graduated scale is a scale with markings that indicate units of measurement. Graduations can be found on a variety of measuring devices, including rulers, measuring cups, and cylinders.

Principles

  • Increments: The increments of a graduated scale are the amounts by which the scale increases when a load is applied. For example, a scale with a graduation of 100g will increase in 100g increments.
  • Spacing: Graduations can be spaced at a constant distance apart, or they can be spaced at varying intervals.
  • Linear vs nonlinear: A linear scale has graduations that are spaced at a constant distance apart, while a nonlinear scale has graduations that are spaced at varying interval

Examples

  • Rulers: Rulers can have fractional or decimal graduations. Fractional graduations are based on fractions, such as 1/2″, 1/4″, and 1/8″. Decimal graduations are based on the decimal system, such as 0.5, 0.25, and 0.1.
  • Measuring cups: Graduated measuring cups have markings that indicate units of measurement.
  • Graduated cylinders: Graduated cylinders have markings for different volumes.
Figure 2: Acrylic Rule

Set-Square

A set square or triangle (American English) is an object used in engineering and technical drawing, with the aim of providing a straightedge at a right angle or other particular planar angle to a baseline.

Figure 3: Geometry Triangle