_________ is a type of scale on which three successive dimensions can be measured.
📝 Detailed Explanation: Understanding Measurement Scales
Different scales are designed for different levels of precision and purpose in technical drawing and surveying. The ability to measure multiple dimensions or units on a single scale is a key differentiator.
The Principle of the Diagonal Scale
A diagonal scale is an advanced graphical scale that allows for the measurement of three different dimensions, such as meters, decimeters (tenths of a meter), and centimeters (hundredths of a meter). It achieves this high precision through a geometric principle.
It works by using a set of diagonal lines to divide a small division on a plain scale into even smaller parts. By reading the main scale for the first dimension, the vertical subdivisions for the second, and the intersection point on the diagonal lines for the third, a very precise measurement can be taken.
Comparison of Different Scale Types
- Plain Scale: This is the most basic type of graphical scale. It can represent two successive dimensions, such as meters and decimeters, or feet and inches. It is not precise enough for reading a third, smaller unit.
- Diagonal Scale (Correct Answer): As explained above, this scale is specifically designed to read three successive dimensions, offering greater precision than a plain scale.
- Scale of Chords: This is a specialized scale used for measuring or setting out angles when a protractor is not available. It is not used for measuring linear distances.
- Vernier Scale: This is not a drawing scale itself but a supplementary device that slides along the main scale of an instrument (like a theodolite or calipers). Its purpose is to read a fractional part of the main scale's smallest division, thereby increasing measurement precision.
- Engineer's Scale: This refers to a numerical scale format (e.g., 1 cm = 20 m), not a type of graphical scale. It simply states a ratio.
💡 Key Concepts for Students
- Two Dimensions (Plain Scale): Measures units and tenths (e.g., 4.7 meters).
- Three Dimensions (Diagonal Scale): Measures units, tenths, and hundredths (e.g., 4.75 meters).
- Angles (Scale of Chords): Used exclusively for angular measurements.
- Precision Tool (Vernier Scale): An auxiliary scale on a measuring instrument, not a drawing tool.