A brief history of the Strain Gauge 1856 Lord Kelvin first reported on a relationship between strain and the resistance of wire conductors. Early 1930s Charles Kearns made the first notable use of bonded resistance strain gauges to measure vibratory strains in high performance propeller blades. He used carbon composite resistors (as used in standard electronic instruments) ground flat and mounted on an insulating strip. These were then cemented onto the propeller blades, and were able to indicate the dynamic strains experienced by the blades. However, these gauges were not very accurate, and due to the resistance stability with variations in time and temperature being poor, the gauges were unable to measure slowly changing or static strains. 1937/8 Arthur Ruge and Edward Simmons (working independently of each other) both discovered that small diameter wires made of electrical resistance alloys could be bonded to a structure to measure surface strain. This type of gauge had the advantage of responding well to static strains. Following this break through, strain gauge measurements were adopted for use in aircraft development programmes during World War II. It was due to the demands of this rapidly growing industry that the important advance into foil strain gauges was made. 1952 The Saunders-Roe Company (UK) were seeking improvements in the performance of the bonded wire gauges to enable their use in more demanding environments. At this time, printed circuits were emerging, and Saunders-Roe developed the idea of making a strain gauge by etching the pattern for the gauge from a thin foil. These foil gauges had some distinct advantages, most notably a reduction in size and production costs. This allowed much more extensive use of electrical resistance strain gauges, and they are the most common type in use today. Semiconductor strain gauges are also in use today, and these differ in many aspects from the metallic wire and foil strain gauges. Most importantly, they produce much greater sensitivity (10 to 50 times), which was at one time thought to herald the downfall of metallic gauges. But, semiconductor gauges are very limited as a general purpose gauge, and so there is a place for both types in modern strain measurement. For details of Strain Gauge Suppliers, click here...

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