Unit 5 Linear Measuring Devices and Comparators

Linear measurement includes the measurement of lengths, diameters, heights and thickness. The basic principle of linear measurement (mechanical type) is that of comparison with standard dimensions on a suitably engraved instrument or device. Linear measuring instruments are categorized depending upon their accuracy. The two categories are non-precision instruments and precision instruments. Non-precision instruments include steel rule, caliper divider, and telescopic gauge that are used to measure to the line graduations of a rule. Precision instruments include micrometers, vernier calipers, height gauges and slip gauges. A wide variety of electrical measuring devices is also available. Electric measuring devices are mainly transducers, i.e. they transform the displacement into suitable measurable parameter like voltage and current. Some of the displacement transducers are strain gauges, linear variable differential transformers (LVDT) and potentiometers. This unit will discuss different type of linear measuring devices and comparators.