Various means like mechanical, optical, acoustical, pneumatic or electrical can be used to measure deformation (strain) of an object. The length of the wire is 25 mm or less. The other gauge is isolated from all mechanical stress, and acts merely as a temperature compensation device (the "dummy" gauge). Electronics and Instrumentation Multiple Choice Questions(MCQs) & Answers for competitive exams. The strain gauges R 1 ∼ R 4 are glue-bonded onto the metal beam supported by a metal cylinder. First, there is the fact that the resistance of most wires changes with temperature. Earlier wire types of strain gauges were used commonly, which are now being replaced by the metal foil types of gauges as shown in the figure below. Bonded wire strain gauges: The bonded metallic type of strain gauge consists of a strain sensitive conductor (wire) mounted on a small piece of paper or plastic backing. A wire gauge was mounted and bonded between two thin pieces of paper. d) infinite insulation resistance. Bonding element in a strain gauge must have _____ a) zero insulation resistance. As the bonded strain gauges are well bonded on to the specimen, the entire strain being experienced by the specimen is transferred to the strain gauge. Considering the mounting, strain gauges can be either bonded or unbonded and based on the construction, we can have foil, semiconductor, and photoelectric strain gauges. Both gauges are bonded to the same test specimen, but only one is placed in a position and orientation so as to be exposed to physical strain (the active gauge). Resistance Wire Strain gauges,with gage length greater than the maximum size of the Coarse Aggregate,typically 50 to 75 mm. Strain gauges. Bonded wire strain gauges exist in three forms, namely, metal foil, fine wire, and semi-conductor gauge. 1.1.1(a) and (b) schematically show a force sensor using four metal foil strain gauges as sensing elements. Unbonded Strain Gauges These strain gauges are not directly bonded (that is, pasted) onto the surface of the structure under study. These short objective type questions with answers are very important for Board exams as well as competitive exams. It is used for high resistance 4. In case of an emergency, the strain gauges can generate a warning so maintenance can be done early to minimize the impact on rail traffic. Q. The grid of fine resistance wire is cemented to carrier. This foil and backing combination are often thinner than a human hair. The strain gauges should have a high value of gauge factor, The resistance of the strain gauge should be as high as possible since this minimizes the effects of undesirable variations of resistance in the measurement circuit. Others include: metallic wire-type, Semiconductor, Thin-film, Diffused Semiconductor, and Bonded Resistance Gauges. ... we need to mount bonded strain gauge on the specim. The metallic foil-type strain gauge consists of a grid of wire filament (a resistor) of approximately 0.001 in. Q1) The detectors used in optical sensors is. Bonded Foil strain gauges The first bonded, metallic wire-type strain gauge was developed in 1938. The value will be printed on each pack of precision strain gauges. i.e. These gauges rely on direct pasting or bonding on the surface of object under measurement. Wire wound gauges are made of round wire of copper-nickel, chrome-nickel, or nickel-iron alloys about 0.0064 cm diameter. There are several types of strain gauges based on the principle of their working viz. A second temperature effect occurs if the thermal coefficient of expansion of the strain gauge wire is This is the reason why they are referred to as bonded gauges. This is attached to two lengths of rebar, one at either end, which in turn are used to transfer strain from the structure to be monitored to the gauge. A brief history of the Strain Gauge 1856 Lord Kelvin first reported on a relationship between strain and the resistance of wire conductors. 5 Figure 16 General arrangement of a bonded-wire type strain gauge The bonded wire gauge has largely been replaced by the foil gauge which has been in production since the 1950âs. c. Laser. Q. Strain gauge sensors are widely applied to measure the piezoelectric displacement. Many years ago there were several brave stress analysts who bonded strain gage sensors to a horse shoe, while the horse was wearing the shoe. In this chapter, one piezoelectric actuator (PZT stack) is used to illustrate the measuring principle of strain gauge sensors. b) low insulation resistance. Bonded foil strain gauges can be as small as 16 mm2 and have strain sensitivity or gauge factor of 2. Bonded wire strain gauge. (0.025 mm) thickness, bonded directly to the strained surface by a thin layer of epoxy resin. Two resistive films are bonded to the PZT stack, as shown in Figure 6.5.The length change of the piezoelectric stack alters the resistance of the strain gauge. The need for temperature compensation of strain gauges arises from two factors. Q. a. Commonly used elements for wire strain gauges are _____ A resistance wire strain gauge has a wire of diameter 0.25mm or less. Considering the mounting, strain gauges can be either bonded or unbonded and based on the construction, we can have foil, semiconductor, and photoelectric strain gauges. Considering the mounting, strain gauges can be either bonded or unbonded and based on the construction, we can have foil, semiconductor, and photoelectric strain gauges. 0 for foil and wire strain gauges. It consists of a very thin foil bonded to an insulating backing, and the foil is etched so that it looks like a long piece of wire that has been zig-zagged (early strain gauges were actually made out of thin wire). The wire grid may be & flat type or wrap-around. In use, the strain gauge is bonded to a surface. bonded wire strain gauges. Hence they are termed as unbounded strain gauges. (0.025 mm) thickness, bonded directly to the strained surface by a thin layer of epoxy resin. These short solved questions or quizzes are provided by Gkseries. There are many types of strain gauges. Types of strain gauge: -Bonded gauges(see Fig. Types of Strain Gauges. Prior to the invention of the bonded wire strain gage , Charles Kearns of Hamilton Stan- dard produced a crude version of the modern-day strain gage in 1936 by cementing flattened carbon composi- tion resistor elements to a propeller blade [12.1]. a. Photodiodes. c) nickel cadmium alloy. 5. Mention advantages and disadvantages.Q. Write a Short note on Bonded Resistance Strain Gauges. Bonded wire strain gauges Strain gauges For excellent and reproducible result .. The Strain Gauge Strain gauge: it is an electrical conductor whose resistance changes as it is strained. d. Only (a) and (b) e. All the above. Strain Gauges have a long history in the safety of rails. 3. c) high insulation resistance. The general construction of a bonded wire type strain gauge is shown in Figure 16. Fig. Bonded wire strain gauges are used on the surfaces of different structures. Wire strain gauges are normally of two types,. Encardio-rite primarily deals with six different types of strain gauges: Model EDS-11V/Hermetically Sealed Vibrating Wire Strain … Derive the expression for the gauge factor of a strain gauge. But some strain gauges are not of an isoelastic alloy. It … It is used for high resistance Chapter One The Strain Gauge Strain gauges measure axial tension or compression with no impact on the rails. Most of the strain gauges are made of constantan alloy which cancel out the effect of temperature on the resistance. mechanical, optical, acoustical, pneumatic or electrical. There are three types of bonded wire strain gauges. The figure shows the example of a wire-wound strain gauges. Model EDS-11V/Hermetically Sealed Vibrating Wire Strain Gage It is suitable for embedment in soil or concrete or for surface mounting by welding on steel structures. b. Phototransistors. 2. An application of stress on the bonded strain gauge causes the electric resistance to … i.e. MCQ ON DISPLACEMENT MEASUREMENT,STRAIN MEASUREMENT,MEASUREMENT OF ANGULAR VELOCITY,ACCELERATION MEASUREMENT. Dynamic strain measurements use _____ a) brass iron alloy. It is used to measure stress and strain on rails. 0 for foil and wire strain gauges. In such cases, dummy gauge is used in the place of R 2 in the quarter bridge strain gauge circuit which acts as a temperature compensation device. Testing was being done to validate the design of a lighter horse shoe intended to reduce the stress and cracking of the horse’s foot while training and racing The metallic foil-type strain gauge consists of a grid of wire filament (a resistor) of approximately 0.001 in. In us this gauge is cemented to the surface of the structural member to be tested. Q2) Optical sensors used for the displacement measurement works on the principal that. The metals can be easily cut into the zigzag foils for the formation of the strain gauges. The strain gauge is connected to a … For example, photoelectric gauges use light. namely, bonded and unbonded gauges depending on the method of fabrication. As stress is applied to the material, the BFSG will deform and the resistance changes. ... A fine wire resistance strain gauge is stretched around the insulated pins. Explain the construction of wire wound strain gauges. 1.1) 1- Wrap-around wire strain gauge It were wound with fine copper wire on a thin paper tube, which was then flattened and stuck to a metal surface. Bonded foil strain gauge (BFSG) pressure transducers & transmitters have foil gauges made from materials such as Constantan which are bonded using industrial adhesives to a stainless diaphragm or beam which is the material which flexes in response to change in pressure. I would like first to explain why we chose the image for this article. Types of strain gauge: -Bonded gauges(see Fig. b) iron aluminum alloy. Strain gauges can be made of metal foil as well as metal wire. Bonded foil strain gauges (BFSG) are metal based foil elements that are incorporated into a flexible electrically insulating material which can then be bonded to a surface with adhesives. The value will be printed on each pack of precision strain gauges. 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