Chapter 8. Measurement of Length
Length is probably the most measured physical parameter. This parameter is known under many alternative names—displacement, movement, motion.
Length is often the intermediate stage of systems used to measure other parameters. For example, a common method of measuring fluid pressure is to use the force of the pressure to elongate a metal element, a length sensor then being used to give an electrical output related to pressure.
Older methods were largely mechanical, giving readout suited to an observer's eyes. The possibility of using electrical and radiation techniques to give electronic outputs is now much wider. Pneumatic techniques are also quite widely used, and these are discussed ...