The type of glue depends on the required lifetime of the measurement system. Strain gauges are attached to the substrate with a special glue. Gauges attached to a load cell would normally be expected to remain stable over a period of years, if not decades while those used to measure response in a dynamic experiment may only need to remain attached to the object for a few days, be energized for less than an hour, and operate for less than a second. In most cases the orientation of the strain gauge is significant. Different applications place different requirements on the gauge. Typical input voltages are 5 V or 12 V and typical output readings are in millivolts.įoil strain gauges are used in many situations. In practice Visualization of the working concept behind the strain gauge on a beam under exaggerated bendingĪn excitation voltage is applied to input leads of the gauge network, and a voltage reading is taken from the output leads. With careful installation, the correct gauge, and the correct adhesive, strains up to at least 10% can be measured. G F = Δ R / R G ϵ GF= is the bridge excitation voltage.įoil gauges typically have active areas of about 2–10 mm 2 in size. A single linear trace would have to be extremely thin, hence liable to overheating (which would change its resistance and cause it to expand), or would need to be operated at a much lower voltage, making it difficult to measure resistance changes accurately. This does not increase the sensitivity, since the percentage change in resistance for a given strain for the entire zig-zag is the same as for any single trace. From the measured electrical resistance of the strain gauge, the amount of induced stress may be inferred.Ī typical strain gauge arranges a long, thin conductive strip in a zig-zag pattern of parallel lines. Conversely, when a conductor is compressed such that it does not buckle, it will broaden and shorten, which decreases its electrical resistance end-to-end. When an electrical conductor is stretched within the limits of its elasticity such that it does not break or permanently deform, it will become narrower and longer, which increases its electrical resistance end-to-end. Physical operation An unmounted resistive foil strain gaugeĪ strain gauge takes advantage of the physical property of electrical conductance and its dependence on the conductor's geometry. Probably the last and most important property was the ease of transmission of the electrical output signal. Additionally, they were simple to install by the scientists, did not cause any obstruction or property changes to the observed object and thus falsifying the measurement results. The strain gauge applications were quickly gaining traction as they served to indirectly detect all other quantities that induce strain. His employer at MIT waived all claims on the right of the invention, as they did not predict the economic and large-scale usage potential. Ruge realized the commercial utility of the strain gauge. Ruge developed a widely used and useful measurement tool due to the lack of an alternative at their times.Īrthur C. The development of the strain gauge was essentially just a byproduct of other research projects. Hanns Meier) had the epiphany of measuring the resistance change in metallic wires caused by strain cemented on the thin walls of the water tank model. He was not able to utilize the standard optical strain measurement methods of his time due to the small scale and low strains in his model. He tried to analyze the behavior of a model water tank installed on a vibration table. Ruge, a professor at MIT, on the other hand, conducted research in seismology. Simmon came up with an original way to measure the force introduced into the sample by equipping a dynamometer with fine resistance wires.Īrthur C. They researched the stress-strain behavior of metals under shock loads. Simmons was involved in a research project by Dätwyler and Clark at Caltech between 19. Ruge independently invented the strain gauge. This resistance change, usually measured using a Wheatstone bridge, is related to the strain by the quantity known as the gauge factor.Įdward E. As the object is deformed, the foil is deformed, causing its electrical resistance to change. The gauge is attached to the object by a suitable adhesive, such as cyanoacrylate. Ruge in 1938, the most common type of strain gauge consists of an insulating flexible backing which supports a metallic foil pattern. The markings outside the active area help to align the gauge during installation.Ī strain gauge (also spelled strain gage) is a device used to measure strain on an object. The gauge is far more sensitive to strain in the vertical direction than in the horizontal direction. Electronic component used to measure strain Typical foil strain gauge the blue region is conductive and resistance is measured from one large blue pad to the other.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |