As the world revolves a myriad of machines work smoothly to keep things going. Massive planes take to the skies in tremendous bursts of power, and at a different level coal powered and nuclear turbines keep the electricity flowing into domestic kitchens. The stresses imposed by heat and movement upon the material components of all the machines that power our lives do not in themselves cause break downs but are the causes that will inevitably result in effects. Engineers measure stress in mechanical components using a variety of means.
A strain gauge is a resistance-based sensor used by mechanical engineers. Strain does not officially have a unit of measurement, but for reference purposes, a special unit of measurement is used. Because the changes in length are often very small, the unit of change employed is expressed as 10 to the power of six, to provide meaningful readings.
There are various types and configurations of sensors. The metal foil gauge consists of a length of thin metal wire wound around a grid called a matrix. This is stuck to a metal backing and then bonded to the object where measurement is required. The gauge is aligned with the line in which stress will occur. As the wire lengthens or compresses, so measurements are taken.
Optical sensors are made of glass, of varying thicknesses. Fibres with a core of 5 micrometers are surrounded by a layer of pure glass with a diameter of 125 micrometers. Different reflection points create optical effects. As these gauges are insensitive to electromagnetic fields they are useful in explosive atmospheres.
Configurations of gauges can be designed to measure various strains that might apply to objects of different sizes and components. For example the bi-axial configuration can measure along different planes, as in a hole or cutting instrument. Here two different appliance are aligned at right angles to a common point in order to measure along different axes.
In addition to measuring mechanically, instruments can be designed to measure thermally. The forces applied to continuously welded railway lines occur vertically, longitudinally and laterally. Configurations of different instruments can provide vitally important data for maintenance crews, and help to ensure the safety of long distance and high speed trains.
It is clear that the strain gauge play an important role across the gamut of industrial activities. In mining, agriculture, architecture, construction and road building there are obvious applications. Less obvious, but equally important are the uses in the media, medicine and legal services. Engineers engaged across all these fields do well to choose the products of reputable manufacturers who can be relied upon to produce accurate measuring instruments.